PART
3
Concepts Related to the Scientific Method
.... _-------_ .. _-----------_..... _----_ ... _-.-----------------------------_._.
INTRODUCTION
I n yo u r work on th e preced ing- pro blems you have learn ed ma ny th ings. For exam pl e.
y O li have d evelo ped an abi lity lO plan ahead . to fo resee di ffic ult ies an d ove rco me them in
advance. Th is is a valu able ability. And , as you learn more chem istr y fro m the problems
in thi s sect ion, th i.. ab ility to plan ahead can be int egrated wit h anothe r skill, proficien cy
in team work. For each assigned problem , arrange an equ itable d ivision of the tasks 1O be
don e with YOU T partner so that eac h of yo u is b usy most o f th e t ime. Pla n YOU T work befo rehand so that while on e par t ner prepares a solu t ion . the ot he r is scn ing u p the apparatu s;
wh ile on e stud ies a refe re nce tex t, t he other carefully reviews the resu lts described in the
laborato ry no tebook s an d then bo th confer, mu t ual ly exchang ing information an d ideas.
Mode rn society is co mplex . T od ay most people work at special tasks, each a mem ber o f a
team : pro ficiency ill tea mwork, learn ed now, will be hel pful later O il.
T he problems listed ill th is secti on d eal p rima ril y with pri nciples that, thus far , yo u
have on ly rea d abo u t. Your instructor lIlay ask yo u , for exa mple , to pre pare a litt le d ecaa nuu inc-s-pcroxod icobalt (I II) terrae lilor -i d c.
O r he lila)' assign YO li the task of pro ving that t he atom ic weigh t of wolfram is
app roxi mate ly 184. Perhaps he will ask you to "how that h ydro gen ch loride can be prepared
by the an ion o f sulfu ric acid on almost an y chloride . You mi gh t be asked to show that nickel
is sta ble in the d ivalent Hate and u nstable in t he tr-ivalen t sta te. Or he m ight assign a pro bleu r from th e list of problems in th is sect ion.
As us ual, you will refer 1O the avai la ble litera ture in the lib rar y and elsewhere. You
will d iseuse th e man cr with yo u r instr uct or an d others. ult imately determi ning a proper
auac k, all the wh ile recording t he necessar y fans and suggestio ns in you r notebook.
O ln .ionsly, 110 lch om tor v u-ork should
that yo u r proposed [noced uve is safe.
Ire
at tempted until
63
Y OUT
instructo r has certified
Prior to perfon niug th e ste ps which you b el ieve will lead to a solu ti on of the problem ,
you will prc pare a written re por t. Th is re port wi ll consist o f th ree par ts:
I. T h e state m ent o f the problem . Copy th e stateme n t from the page.
II. The p roposed method of attack . Descr ibe
III
shor t im pe r ati ve sen ten ces t he step s
to be ta ken.
II I. Demon strat io n of co nsoua ucc. State why your p roposed m ethod will r eall y yield
a solu t ion to you r proble m . Show that the ste ps in you r att ack are pertinen t.
Subm it th is rc port, an d your no te book, to yo u r instructo r. H e wi ll exam ine the report
and , pe rh ap s suggesti ng a few changes, cert ify th at your proposed m eth od is satisfac tory.
T hen carry ou t you r procedure, re cording all impor tant ob serva tions in your no teb ook.
Rewri te, or n eatly correct wh ere n ecessary, you r original r e por t an d add a fourth
sccuon:
I V. The so lu tion of the problem . Show, by citi ng th e res u lts o bt ained in the Iabora .
tory, that th e problem is in deed solve d . If req ui red by th e nature of the problem , include
sam ples of mater ial p repare d in the la bora to ry.
Su b mi t th e ent ire r eport for grad in g. T he gr ade will be deter mined b y co ns iderat ion
of thes e po in ts:
I.
2.
3.
4.
5.
G.
T h e aptness an d efficienc y of the p lan used to ob tain an answer to the p roblem .
Agreemen t o f the res u lts ob tai ne d wit h acce p ted ch emical fact s and principles.
T he m e of go od En gli sh gr am ma r.
T he clarity of your exposit io n.
You r la bora to r y techniq ue .
P ro pe r usc of your labo rator y notebook .
THE PROBLEMS
Group A. A Study of Principle s
l. Sel ect an y ind icator you ch oo se and d etermin e its jJK va lue .
2. P ro ve the valid it y o f Cha rles' law.
3. Pr ove that any salt yo u choose d issolves in wa ter in the form o f io ns.
4 . Show, fo r an y two ele me n ts you choose, that th e law of m u lt ip le proportions is true
for two or more com pou nds of these two clem ents.
5. Show th at m etals below hy d roge n in the electromoti ve ser ies will, u nd er certai n
con d it io ns, d isp lace hyd roge n fro m some acids.
6. Prove Dalto n 's Law of Part ial P r essures.
7. Show th at oxid es o f m etals h ave bas ic properti es and th at oxid es of nonme ta ls ha ve
acid ic properties.
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8. Show tha t, in the series 1\', P, As, Sb . Hi, the metallic character of these el ements
inc reases as atom ic n u mber increases.
9. Show that , because o f h yd ro lysis, a solut ion o f ammoruum sulfide has a lower
concentra tion of sulfide ion than a solution of sod iu m sulfide of the same sto ich iometric
co ncentra t ion .
10. By usin g the Dulong-Petit rel ation and su itable laborator y data , determine th e
approxima te atomic weight of any ele me nt you choose.
Group B. A Study of Principles (continued)
l. Determine the value of R , the gas constant.
2. \ Vhat is the
aceta te per liter?
pH of a solu t ion con taining
I mole of ace tic acid an d 2 mo les of sod iu m
3. Prove the validity of Boyle's law.
1. Show th at , compared wi th each o th er, ti n (II ) su lfide is basic and tin (I V) sul fide
is acid ic.
5. Sho w that the p resence of ammonium aceta te will affect the d egr ee of ionization
of acetic acid, whereas the presence of ammonium ch loride will not affect the degree of
ionizat ion of h ydro chloric acid.
6. Sho w that it is possib le, under proper conditions, for a meta l that is below another
in th e ele ctromot ive series to form ions, wh ile the mo re read ily oxidized metal is precipita ted
fro m so lu tio n.
7. The properties o f an el ement can often be in ferred fro m the beh avior of other
d ements. Demo nstrate, b y labora tor y tests, but witho ut testing every possib ili ty, that it is
reas onable to state tha t all nit rates are solu ble.
8. Sho w that the degree of h ydro lysis of a solu t ion of a salt o f a weak acid an d stro ng
base, selected b y yourself, d epends u pon the temperature of the solutio n.
9. Show that the electron ega ti vity of the ha loge ns, chlor ine th rough iodine, decreases
as the ir atomic n um ber increases.
10. Sho w that, in a solution con tai ning h ydronium and sulfid e ions in equ ilibrium
with hydrogen mo no su lfide ion s and d ihyd rogen sulfide, when the h yd ro n iu m ion co ncentrat ion is increased by a fact or of 10, the sulfid e ion co ncentrat ion is decreased by a factor
o f 100.
Group C. The Proper ties of Substa nces
l. Sho w th at ammon iu m sulfat e hydrolyzes in sol u tion.
2. ' Vha t is the atomic weigh t o f ch lorine ?
3. What is the ion izat ion cons tant of acetic acid?
65
4 . W h at is th e equ ival en t weight of tin ?
5. 'Vhat is the valence of alu m in u m?
6. Usi ng dat a ob tained in th e la boratory, p re par e a gra ph sh ow ing th e density of
liqu id wa te r as a func tio n of its tem pe ra ture over the range from 00 C to 100 0 C.
7. ' Vhat ar e th e valence s of ir on?
8. Sh ow that a fused salt will con d uct an electr ic cu rren t.
9. Sh ow that the boi lin g po int of a homologous ser ies of alco h ols is a fu nct ion of their
molecu lar weigh t. N ote: u se on ly a few mill il iters of eac h alcohol.
10. Show that iod id e io n is a reduci ng age nt.
Grou p D. The Properties of Substa nces (continue d)
1. List an y four ox id izing agents in order of decreasing ox id izing po wer an d validate
the list.
2. Show th at potassium d ichromate is an oxi d izing agent.
3. w ha r is th e atom ic weigh t o f magnesium?
4 . Select severa l substanc es and show, by la borato r y tests, that they are all reducing
agents.
5. t vhar is the fJH o f a O. l -Af solution o f acet ic ac id?
6. Show that t he molecu lar weight of oxygen is 32. Caut ion : Do n ot pr e par c element al ox ygen (if yo u d ecide to solve the prob lem in this way) by h eati ng a ch lo rate or
perch lorate.
7. P rove t ha t sod iu m carbona te will react with calcium hydrox ide.
8. By m eans of a su ita b le appara tu s, study the p rope r ties of severa l selecte d me ta ls to
deter m in e wh ich w ill and wh ich wi ll not , nell in the finely div ide d state , react with hot
steam.
9. Show that acetic aci d rea cts more slow ly with l ine than docs h yd roch lori c acid
of the sam e m ol ar ity.
10. Show that the value of any selecte d p hysical pro perty of severa l compou nds
isom er ic to each o ther, wh ich yo u select, de pend s u Jlon th e molecular str uct u re o f the
Isomers .
Group E. Ana lytica l Chem istry, Qualitative Ana lysis
l. Show that acetaldeh yde is an ald ehy de.
2. ' Vha t products arc for m cd in the comb us ti on of the fuel gas used in yo ur
laboratory?
3. ' Vhat is the sm allest con centration of iod ine that can be de tected by the starch te st?
66
4. O f wh at is the at mos p here com posed?
5. Show that heel' co n ta ins arsen ic.
6. Show that gel atin e coma ins nitrogen .
7. Show that the ion ,
Cll Br ~ = ,
can exi st in solu t ion.
8. Show th at there is a car bony l group in the acetone molec u le .
9. Se parate an int imat e mixtu re of 5 g of sodi um ch lor ide and 5 g of sucrose.
10. Determ ine t he lean amount of arsenic and of antimony that can be detected h y
the Xla rsh te st.
Group F. Analytical Chemistry, Qualitative Analys is (continued)
As required for ea ch problem , prepare solut ions approximatel y O.03-M in each ion
listed . Deter mi ne, and te st, methods for se par at ing each ion from t he o thers present in
the same solu t ion.
l. AIH +, Ag +, Ba H .
2. H gt H , Cll H , Pb H .
3. Cu ' ", Sn ++++, Fet ".
.1. Sr H,
~ l g H,
Zn H .
5. II g H , Ag", Ca H .
6. BaH, C u H , Ca H , H g H .
7. AI H +, Zn H,
~l gH , ~l n H .
8. II g H , Ca " , Ag -, xs -.
9. Cr, O r- . Fe ++, AP ++. Zn ++.
10. Sn t "t". ClI H , Ag", :\In ++ .
Group G. Analytical Chemistry, Quantitative Analysis
I. As accu r ately as po ssible, dete rmi ne the percen tage of sod iu m ch lorid e
represen tat ive sam p le of t he rock salt in th e bo u le o n th e side she lf.
III
a
2. " ' hat is th e form u la of n ickel su lf ide?
3. \ Vha t is th e per ce n t o f acet ic acid ill vinegar?
4 . \ \' hat is th e value of X in any one , or more, o f t he following or sim ilar for m u las :
C u S O~ ' X Il 1 0 , Z\' a 1 B ~ O .· XH 2 0,
CaSO-l'X H 1 0 ?
5 . Sh ow that the m olecu lar we igh t of am m on ia is a pp ro xim ately I i .
6. Deter m in e th e am ou n t of citric acid as gra ms per 100 m l (you m ay assume that all
the ac id p re '>elll is ci tr ic acid ) in a sample of citr us frui t juice.
67
7. Determine th e solubilit y produ ct of an y ..lightl y solu blc salt you choose.
8. Determi ne the mol ar co nce nt ration of amm o nia in the di lute ammonium h ydroxide solu tion o n th e side shel f.
9. \ Vhat is the co mpos it ion of constant-boiling hydroch lori c acid?
10. Determi ne t he first and second ion izat ion constant s of ortho phosphoric acid .
Group H. Anal ytica l Chem istry, Quantitative Ana lysis (continued)
1. Show t hat 13
~
of calcium carbon ate con tai n ap proxima tel y 1.2 g of carbon.
2. Show that th e molecul ar weight of carbon d ioxide is approx imately 44.
3. Pro ve tha t water cons ists of h ydrogen and ox ygcn in th e ra tio of two atoms of
hydrogen to one atom of ox ygen.
4. Determ ine th e percen tage of hydrogen in a su itable piece of sto ne. (N ote: N ot
all kind s of rock conta in hydrogen .)
5. Confirm thc statement, as given o n the label by the man ufact urer, of the per·
ccntage of ni tric acid in a bou le of concent ra ted acid.
6. Det erm ine the value of th e instabil ity consta nt of the complex ion Ag (XH 3)2-.
7. Determine the purity of a sample of bak in g soda . calcu lated as perccntage of ::'\a 2 0 .
8. Prove th at when 100 m l of I -N H CI solut ion are added to 100 m l of I-N i\'aOH
solution, 0.1 eq uiva lent of water is form ed.
9. By a proced ure which re q uire s ti trat ion . de termi ne the carbo n dioxide cont ent
of th e a ir in yo ur lungs as a fu nction of the length of t ime after inh alat ion .
10. \\' ha t is th e purity of the potassium pcrm an ganate in the bou le
011
the side shelf-
Group I. Pre para tions
1. Start in g with re sorcinol and ph thalic an hydri de. prepare a few grams of fluoresce in.
Pro ve th at your prod uct is reasonably pure.
2. Exercising all possible precautions to avoid loss of and contam ina t ion of mater ial .
prc parc pure sod ium chloride from th e rock salt on the side shelf.
3. Convert an y solu ble sulfate to the corres ponding chloride by two d iffere nt me th od v
an d con firm yo ur resu lts.
4. Prepare an aq ueous collo idal d ispersion, free of dissolved elect rol ytes. of ' a ny
chosen water-insoluble su bstance.
5. Purify a few grams of crude borax .
6. Prepare a Iew grams of mon osodium d ihydrogcn orthophospha te and of d isod iurn
mo noh ydrogen ort hopho sphate by mix in g the proper q ua nt it ies of ortho ph ospho t ic acid
and sod ium hydroxide. Prove tha t yo u have pre pared the se salts "
68
7. \ Vithout ut ili zing p u re or impure gasco us oxygen, preparc a sample of purc
magnesiu m oxide. Sho w tha t your product is p ure.
8. In the synt hes is of Congo red, whi ch includes a step requiring the diazotizatio n of
bcn zid enc, wha t variab les affect the yield ?
9. Prepare a few grams of zinc chloride , start ing with zin c su lfate. Prove that you
h ave ob ta in ed the desired prod uct.
10. Prepare 10 rnl o f etha nol.
Group J. Preparations (continue d)
l. Prepare 2 g of co ppe r (I) su lfide and 2 g of cop pe r (II) su lfi de .
2. \ Vhat factors affect the yield in the syn thesis of a -prop yl acetate in the laborator y?
3. P repare a small q uant ity, about 0.00 1 mole , of hydroge n b rom ide.
4. P repare a sma ll quan ti ty o f magn esium nitr-ide an d cert ify its pur ity.
5. P rep are a few gra ms of any salt o f a p hospho-oxy acid, salts of orthophosphoric acid
excl u de d , and confi r m yo ur synthesis.
6. P repare a few grams of coarse filamen tous rayon.
i . Prepare a few grams of an y water-soluble wer ner comp lex com po u n d tha t you
choose.
8. P repare I g of iodine.
9. Prepare a few gra ms of an y water-insoluble 'Vern er com plex co m pound t hat you
choose.
10. Prepare 5 g of sod ium h yd rogen su lfa te. P ro ve tha t it is sod ium hyd rogen su lfate.
Group K. Technique
l. At wha t tempera ture is the solu b ility, expressed in grams of salt per lit er of wat er,
of sod iu m ni tra te and potassium n itrate the same?
2. Demo nstrate th at air h as weigh t.
3. Show tha t ni trogen , o btained by th e removal o f oxygen, carbon di oxide, and water
Ya po r from the air, is d ifferent from ni trogen ob tained b y the carefull y co nt rolled react ion
be tween ammoni um ch lori de and sod iu m nitrite. Ca ution : Un less the reaction between
:--: H~CI a nd :'\a:\"0 2 is carefu lly controlled , the nitrogen may be released exp losivel y.
4. Show that the su m of the con d ucti vities of a O.I ·.:\J sod iu m ch lo ride solu tion and
a O. l -M silve r n itra te sol u rion is gre ater tha n the cond uc t ivity o f an equal vol ume o f thes e
two sol ut ions mixed toge ther.
5 . Show, us ing laborato r y data, th at the logari th m o f the yapor pressurc o f an y
sta nce you ch oose is a lin ea r function o f the recip roca l of the abso lu te tcmpera tll r ~
69
~
6. Show, for a pai r of su bstances wh ich you cho ose, that whe n a solute is d issolved in
a solvc u r, the volu me o f the solut ion is not equ al to the sum of the volu mes of the separa te
co nsti tucnts.
7. Show t ha t act ivated alu m ina 'will ad sorb a gas.
8. Select any three ind icators whic h change color in the p H ra nge 4 to 9 and de te rmi ne , to the nearest half j )H u nit, t he re lat ion between color o f each ind icato r and the J)l!
o f the solut io n in whic h a few d rops of the indicator so lut ion ha ve been d ispersed.
9. Det ermi ne t he weigh t of a p iece of zin c wit ho ut weig hing it or any o th er su bstance
o n a balance or other weigh ing d evice.
10. Sho w that th e su m o f the cond uctivi t ies of a n.I -At acet ic acid solu tion and a O.l -AI
am mon iu m h ydro x ide solution is less than the co nd uct ivity o f a mi xture of eq ual volu me s
of these two solu tions.
Group L. Techni que (continued)
1. Prepare a few m illiliters of any easily liq uefied gas.
2. From the stand poin t of cur rent cost and from labo ratory data , d ete rmine whic h is
the best, next best, nex t to poores t, an d poorest, antifreeze : sod iu m sulfa te, calciu m chloride,
glycerine, ethyl alcohol.
3. Determ ine th e d ensit y of a large piece of mo ssy tin .
4. Compare the prod ucts formed in the d estruct ive d istilla tion of bitum ino us and of
anthracite coal.
5. Measure the rel at ive h umidi ty o f the ai r in the laboratory.
6. Using a calomel electrode, a plati nu m electr ode, an d a po ten tiom eter, tit rate
O.Ol -Al iron (II ) su lfate solution (in a beake r) with O.OI-At po tassium dichromat e solu tion
(in a b u ret ). Draw a titration cu rve an d determ ine the endpoin t.
7. Using data ob tained by steam di stillation , an d oth er necessary information fro m
reference wor ks, ca lculate the molecular weigh t o f nitrobenzene .
8. Show that the su m of the condu cti vit ies of a I-M h yd rochlori c acid solut ion an d
a I-At sod iu m h ydroxide solut ion is greater than the con d uct ivity of a m ix tu re o f eq ual
volu mes o f these two sol u tions.
9. Show that acti vated charcoal will adsorb a solute from a solu tio n .
10. Show th at acet ic acid is d imeric when d issolved in car bo n tetr achlorid e.
70
Appendices
~_._._---- - -- - - - -- --_._._._--_._-_._-- -- -_._._._----- _ . _ - - - - - - - - - - - - - - - - - - - - -
SAFETY IN THE LABORATO RY
If good pr acti ces an d co mmon sense arc hab it ual in the la boratory no one w ill suffer
fro m an u nex pected ser-ious accident . BUI if the contrary is the r u le d isastrous r esu lt s will
almost surel y fo llow. It is u p to you. T he ins tructor wi ll do all he call to prc\'e nt accidents.
but he cannot carr)' out this duty without your fu ll coo pe rat io n . At all times be aware of
the consequences of your actions. If an accident docs ha ppe n , remain ca lm and seek the
assista nce of yOUT in structor at once.
Var iou s precaut ions are listed in th is book on preceding pages and in this sect ion.
Y OUT in structor will ad d rul es which ap p ly to you r part icu lar situat ion. For yo ur ow n sake
an d for the sake of others . follow these d irect ives h abitual ly. Be fu ll y acq u ainted wi th
the rules listed between pages I an d 30 and wit h those th at follow here :
I. H orse play in th e la borato r y is str -i ct ly p ro h ib ited .
2. A ll acciden ts, 110 ma tter how m in or , m ust be re ported to th e instruct or, prefer ably
immediately after they occu r, but at least within mi n utes after they ha p pen .
3. If YO li propose to per form an expe rim ent , ch ang ing th e deta ils or cond iti ons fr om
th ose prescribed in yo ur r epor t , b y your instr uc tor, by a laboratory m anual you h ave used
for ref er ence, or b y any o th er r eferen ce th at you hav e fo und . be sure to obtain the approva l
of you r in stru ctor prior to carrying ou t t he procedure.
4. " 'ear safety glasses at all t imes in the laboratory .
5. wear a la borato ry apron at all times in the laborato ry.
6. \\' h en acid... or ba ses are spil led upon th e clo thes or skin , flush the affecte d are a
im m ed iately w ith copious qua nt ities of water and ask a fellow student to ca ll the instr uctor.
Par ti cularly, im medi ate flu sh ing is de manded if the eyes have been splashe d wi th liquid .
7. Ea t ing and smoking in the laborato r y arc p roh ibited . Be very car ef u l not to drink
an y liquids, even water, in t he laboratory.
8. Coats, hats. books wh ich will not be u sed d uring the lab or ato r y period, and o ther
personal effects shou ld be deposite d in th e spa('c provid ed-outside th e la boratory r oo m .
9. St r ik e-an ywh ere ma tch es sh all no t be mel! u n der any circu mst ances. Safety matches
71
or flin t lig hters o nly are acce ptable. If safety ma tches are used, put a little water int o th e
con tainer required by rule 10 and douse the matches in this ' ....ater when t hey are di scarded.
10. I nsolu ble refuse, such as small pi eces of pa per, wood, glass, etc., shall be deposited
o nly in the refuse cans, never in the sink, nor on the floor. I n most cases, th e small plast ic
co nt a iner or " tin" ca n at yo ur work space will be su itable. If dead matches are to be deposited in your ind ividual container, begin your laboratory work by puttin g a l ittle wat er
in yo ur conta iner. At the close of each labo ratory period th e refuse accumulated in the
individ ua l containers is to be transferred lO the large refuse cans pro vided by the janitorial
staff.
I I. Apply th e d irect heat of a flame only lO th ese piece s of eq uip ment: beakers, test
t ubes, evapora ting di shes, cr uci bles, glass tubes an d rods, wire gauze, an d ot her meta llic
objec ts. Especia lly, never put a flam e di rectly u pon : gr ad uate cyl inde rs, bo ttl es, b urets,
mortars, pestles, th ermometers. These o bjec ts break spectacularly whe n heated stro ng ly!
12. Large quant it ies of water or ot her liquids spilled u pon t he floor or bench top sha ll
be clea ned up as soon as possible by the st uden t re sponsible. If the liquids are corrosive
or flammable, ask the instr uctor for assistan ce.
13.
WE ALL HAVE A DUTY TO PROTECT T HE ENV IRONM ENT.
Dispose of the excess reagents and products of reactions according to the procedures
described by your laboratory instructor. Do not dispose of any substances except water. water
and detergent or water and soap into the drain. Some of the reagents and products of your work
would not cause harm to the environment if they were disposed of down the drain. On the
other hand. some could be seriously harmful. Since it is not practical to distinguish which is
which. follow the rule and dispose of all chemicals and products as your instructor directs.
14. Bot tles of reagen ts sha ll be returned to the side shelf from whence the y were ta ken
as soo n as possib le afte r a student is finished with th em . T he)' sholl not remain at his bench
area. w hen empty, rea gent bo tt les shall be taken lO the stockroom for replen ishing. The
student ,v-ho empties a bottle is re sponsible for thi s acti on.
15. At the close of each laborat or y per iod , each student will po lice the laborato ry
ben ch area and floor about his assigned space, leaving it as clean as, or clea ner tha n, he foun d
it. All water, gas, compressed air, ctc., cocks will be secured befor e th e stud ent leaves for
the day.
72
THE WRITTEN LABORATORY REPORT
As a college grad ua te not too lon g from now , and perhaps as a scie n t ist. teacher, or
d octor, as wel l, you will be requ ired to make reports, wr itten a nd spoken . I n ma ny cases,
the o nly way ot hers will be able to judge you r competence will be by observing what you
wr ite. o r speak. It is q u ite possible th at you r em ployer will kn ow little or nothing of you r
tech n ical ab il ity. He will determ ine yo u r wort h to h im by what he unde rstands from your
reports. Th is is pa rticularly true o f chemists, phys icists, and other scientists. It is not
qu ite as applicable to engineers, for with them, a su pervisor can see wha t they have built.
It is less applicable to physicians, for the pat ient can judge in part by the re sults of the
treatment which is recommended. Bu t it remains true for almost all types of p ro fessional
work: A person is judged to a great extent by the way he wr ites and speaks. T herefo re it
is essen tial that you begin to learn , here and no w, to wr ite and to speak wel l.
Ho w can you learn to wr ite and speak well? If this were a co urse in English we mi ght
tell you about the elements of style : u n ity, force, beauty, di ct io n, contrast, and a host of
others. Yo u shou ld learn about these things. A list of good reference works treating of
these matters. and other things, is added at the end of this d iscussion. Do no t try to read all
of the m now . (You mi gh t just browse through a couple, to sat isfy your curiosity.) \ Va it
until yo u graduate ; then , wh en you have more leisure, read some of the m . To enco urage
you to do this, it can almos t be gua ranteed that if yo u do read severa l of the references
listed your salary will in crease by at least five per cent , or more, whe n you r employer
notices the re sults in your work .
W hy will yOll be req uired to report in wr it ing, or ora lly? Co nsider yo u r employe r as an
inve stor. He has, eac h pa y day, invested a certa in amo u nt of money in yo u. Obviously, he
wants to kn ow whe t her h is in vestment is a good one, and whether he can , for eac h do llar
he pays you, get back more than a dollar from his custome rs. H e pays yo u to do the work
assigned, th is is true. But he must know that the work assigne d is o f value to h im . In a
repor t to your emp loyer you will recommen d th at certain act ions, p rofitabl e to him , be
undertaken. Now it may be very true that th ese recommendations arc profitable, and that
yo u kn ow the y are so. But you must convince yo u r emp loyer th at your recommendations
are profitabl e, and this re q u ires a certa in skill in writ ing or spea king.
Yo u m ust , in other words, write or speak so that you r reports are u ndersta ndable to
your em ployer, so that he sees d earl y that the act ions you recommend are sou nd ly based
upo n the result s of your work in the laborator y, so that he will agree tha t th e act ion proposed
is pro fitab le.
And th is is the first point. A report must be pre pa red with th e read er in m ind. Remember it wel l. A re po rt m ust be dear to the read er.
How can a report be made dear and u nderstan d able? Th is is m uch too lengthy a su bject to co nside r in detail he re . T he references listed bel ow contain most o f what you need
to kno w. \\re will consider only a few tricks.
First: Be sure that you understa nd the matter you wish to report on. T his is the most
important requ iremen t. Most persons know of and lise the other tricks listed below. But
73
few pay su ffi cient attention to th is first point , even th ough it is ob viously th e most importan t. This er ror is su ffi ciently widespread to warra nt a st r ict in junction : B efore yaH
wr ite a repo rt, )'0 11 shou ld knoiu so much about the su bje ct th at it wou ld not be [easi ble to
unite down all you knoio in a report of reasonabl e leng th.
It is as sim p le as th at. If in wr it ing your repon , you tell all you know about the subject ,
your re port is almost cer ta in to be foun d unsa tisfactory b y you r emplo yer. Ei ther shor ten
th e re port, or lear n more ab o ut th e m ater ial , preferably t he latter.
Beg in now to cultivate th e habit o f thorough in vesti gation . This requ ir es four d ifferent act ivities, listed in order of in creasin g im por tance : ask q uest io ns of you r fellow stu dents;
r ead all you can a bo u t the topic ; see yo u r in st ructo r and ta lk over the problem wi th h im ;
th in k a bo ut what you ha ve lear ned . Then , eve n in t h is cou rse you will know m or e ab out
you r prob lem s tha n is req ui r ed to be written in yo ur r epons.
Aga in, the ou tstan d in g im port ance of th is precept can no t be over em pha sized . It is,
b y far, the most im portant secr et of good r epon wr it ing.
Second : Use the ru les of good gr am ma r. Correct spell ing, p roper punctuation , ag reemcn t be tween su bject and verb , consisten t use of verb te nse, and so on .
T hi rd : Arran ge your exposition in an orderl y way. The o ut line for r eports described
in th is ma nual was design ed to help you wr ite an or der ed re port. \ Vithi n the lim itat ions of
the o u tline , yo ur tas k is to sta te the most im portant thing first and the lea st im po r tant
thi ng last , wi th the o th er items in between , in ord er.
Fourth : A tt end to these m iscell aneo us suggest ions: A vo id the use of long sen te nces
as a genera l ru le. Be su re th at you kn ow the m ean ing o f the words you u sc. Use simp le,
neatl y d r awn sketches to su p port your exposition . Sp ice yo ur r epor t with a little humor,
a good met a p hor or a we ll-tu r ne d phrase, b ut do so wit h pru dence. w r h c, or typ e, your
re port as leg ibl y and as neatly as you can. Rer ead th e ent ire re pon no sooner tha n 12
h ours after yo u h ave fin ished it, correct ing errors that we re mis sed befor e. If possible, h ave
some o ne else read it over an d su gges t correc ti ons.
F ift h : Above all , keep the purpose o f the re port always in you r min d . Then , write
the report , no t so that yo u can understand it , bu r so th at it is clear an d und erstanda ble to
the reader. Benjami n Fran klin ha s sa id: "T o be good , it ought to ha ve a ten dency to ben efit
the reader , by improvin g hi s virtue or his knowled ge ... It sho u ld proceed regu larly . . .
d isti nctl y an d clearl y without con fusion . The words used shou ld be the most expressive
that the language affords, provid ed tha t they ar e th e m ost generall y u nderstood ... T h e
whole shou ld be as short as po ssible, cons iste nt wi th clear ne ss: the words sho u ld be so
placed as to be ag reea b le to the ea r in re ad in g ; in su m m ary , it sh ou ld be smoot h , clear, and
short, for the co n tra ry q ual it ies are d ispleasing ."
74
REFERENCES
A M nnuol of St yle, I l th ed., U . of Chicago (1949).
Baker. S., "Scho larl y Style, or the Lack Thereof ," B ull. Am. Assn. U nw. Proi., 42. 464
(1956).
Harmn , ]., " Eng lish as She's not Taught, " Th e A tlan tic M ont hly. 192, 25, (Dec. 1953).
Brooks. C . and \ Varren, R. P., M odem R hetoric, H arco urt Brace (1949).
Fowler, H . ' V., a nd Fowler , F. G ., T he King's English, Srd ed .. Oxford U. P. ( 1930).
Cowers, E. A., Plain W ords: T heir A B C, Knop f (1954).
Harbarger, S. A., et al., English for E ngin eers, 4th ed., "( cC raw-H ill (1943).
H ewitt, R . '\1. , T he Physician. W riter's Booh, Sau nders (1957).
H odges,
1. C., H arbrace
Co llege H andbook , 4t h ed. , H ar court Brace (1956).
Kap p, R . 0 ., T he Presenta t ion of T ectnucal I niorm ation, Macm illan ( 1957).
.\I illcr , \\t.
J., and
Sa idla, L. E. A. , Eds., E ngineers as W riters, Van Nostrand (1953).
vk Canney, E. 5., R ecurrent M alad ies ill Sch olarly W riting, U. o f
~I ic h i ga n
(1953) .
:\IcCartney, E. S., " Does \ \'r it ing Make an Exact Man>," Science, 119, 525 (1954).
N elson ,
J. R.,
JVritillg th e T echnical R eport, Srd ed., :\IcGraw-H lll ( 1952).
Xichols, " '. T ., "T he Technical Report Bugaboo ," Ch ern. and Eng. Ne ws, 26, 602
( 1948).
Orwell, G ., " Politics and the Engl ish Lan guage," in Shoot ing an Elephan t, H arco urt
Brace ( 1950).
Perrin , P. G. , W riters G u ide and I n dex to English , R ev. Ed ., Scott Foresman (1950).
Roberts, P., Undersunut ing G ram m ar, Harper (1954).
Ski llin , M. E., and Gay , R . M ., W ords in to T y/)e, Appleto n-Centur y-Cro fts ( 1948).
Stewa rt,
J. L. , Ex position
for Scie nce am i Te ch ni cal S tude nts, \Vm . Sloa ne ( 1950).
Struck , H . R., " R ecom mended Die t for Padd ed tvr iti ng." Scie nce, 119, 522 (1954).
w add ell , R., G ram mar an d Style, Dryde n ( 195 1).
\\'all , F. E., " T hc Essent ials of a G ood Re port ," ] . Chem. Edu c., 24 , 127 (1947).
weil. B. H ., Ed., Th e T ech n ical R epo rt. Rei nhold (1954).
J. H ., " A Few H ints on \ \ 'o n l Usage," ] . Chem. Ed uc., 33, 577 ( 1956).
\ \' il..on, J. H ., " O u r Co nst antly Changing Language," ] . Ch ern. Ed uc ., 34, 44 7 ( 1957).
w ilson.
75
SOME UNSOLVED PROBLEMS
By th e tim e yo u han progressed in a per u sal of the m an ual to th is page, several in te res ting ideas have n o do u bt come to m ind . One, pe r h ap s, is that all the prob lems on the
p reced ing pages have al re ad y been solved an d you r task was r eall y to solve them all over
again - a som ewhat u n profi ta ble occu pa tion. H owe ver, several p roblems for wh ich the
ans wers ar c no t known arc listed below. T hese prob lems are o nl y a few o f ve r y, ver y m an y.
T hey have be en selected for in clusion he r e on the basis of thei r sim plicity o f presentat ion .
(T he re ar c many other p roblems, some mor e interesti ng, n o dou b t , than the ones posed
here, t hat ca n no t be easily descr ibed to th e b egi n ner ill scicncc.) Also , b ecause of th eir
sim pl icity , we do have a loose sort o f ex planat ion for a few o f the problems in th is list. You
ma y even be aware of some of th ese expla n ations. Bu t th ey arc not solved in any real sense ;
th at is, for those for whi ch we han a h ypothe sis, the h ypothesis is doub ted b y at least some
o f those who h ave cond u cted tes ts in their la bo rator ies. H ence they arc, all of the m ,
unsol ved .
Later on , yo u m ay be the on e to conce ive o f an accepta b le exp lan at ion for a few o f
these. Let th is be you r cha llenge!
I. To 200 m l of bo ili ng water , ad d , with st irring, 0.5 g of each of the follow in g dyes:
Sudan red , su lfan il b lue, an ili n e yell ow. W hen the dyes ha ve d ispe rsed , ad d sm all swat ches
of co tt on , silk , woo l, an d acetate r ayon to the h ot liquid . Aft er a few minutes r em ove the
p ieces o f clo th and r inse in ta p water.
Wlry arc the pieces of clo th d yed di fferen t colors?
2. '\'ash an ar ti cle soiled with greasy and with no ngr easy d irt
solution .
W hy is th e ar ticle clean ed ?
111
a soap or de terge n t
3. P u t a bo ut 50 0 n il of wa te r in a large beaker an d hea t it to boi ling. Cont inue to b oil
the wat er vigorously; note th at th e bub bles for m fro m fixe d spots o n the bo tt om, or sides,
o f t he beak er .
\Vhy do b ubbles form from particu lar spots when the water is b oi led vigoro usly?
4. Add 5 m l of a n . I-.N silver n it rat e solut ion to 5 uil of a O.I -N KBr solut ion. Filter
o ff the prec ipi tate wh ich is form ed am i cxp ose it to a strong li gh t.
\V h y d id th e silver br om ide darken ?
5. Clea n I ml of m ercu ry by sh ak ing it vigoro usly for on e m in u te in a test t ube con ta inin g 10 m l o f I-M n itri c acid . D iscard the acid an d wash the m er cury with dist ill ed water.
P ut the m cr cu r y 011 a clean watc h glass and ad d enough 5-N su lf u r ic acid to cove r the
m ercur y co m pletely. Ad d I 1111 o f O. I-.M po tassiu m permanganate solu tion to the acid an d
st ir ge n tly. (If the m crcury at th is po int is bro ken lip into seve ra l glob u les, collect it into
on c glob ulc .) \ Vith a steady hand , p ut the po int of a steel sewing n eed le u nder the surface
of thc aq ue ous so lu tion an d li ghtl y touch the side o f th e m er cury glob u le , a few de gre es
ab ove its "eq u ator." H ol d th e need le ste ady. R h yt hm ic act ion will co nt inue fo r several
seco nd s.
Wh y d ocs the m crcury pulsate?
76
6. Prepare a collod ion bag sim ilar in size and shape to a test tube. H alf-fill the bag
with a sol u tion co nta in ing 0.1 g of po tato starch and 0.1 g of sod ium chloride per 100 ml .
Suspe nd the half-filled bag in a beaker o f d ist illed water. From t ime to t im e test the di stilled
water for the pr esen cc of CI- ions and for the p resen ce of sta rch.
' Vh y does the electrolyte d iffuse through the collod ion membrane, wherea s the sta rch
does not?
7. I n the hood , pass a little ph osp horo us t rihydr id e (or arsen ic tr ih ydride or antimon y
u -ihydri d e) in to a O. I-M solu tion of silver n itrate. A yello w p recipitate whic h turns black
in a few ho urs or less is formed.
' Vhat is the nature of the yellow precip itat e?
8. Mi x 2 g o f finel y d ivided P b aO ~ with 2 g of finel y d ivid ed clea n sa nd. Put 50 m l
of water and 50 m l of paraffin oil in a tall glass cylinder. (A grad uate will do , bu t the good
chem ist uses a grad uat e on ly for mea suring vo lumes, no t for the p urpose o u tl ined hcrc.)
Add the lead ox ide-sand mi x ture, and with the pal m of your han d over the mou th of the
cylinde r, shake vigorously for several m in ut es. T hen let the cylinde r a nd its co n te n ts sta nd
un d istur bed for a few min u tes.
' Vh y is the lead ox ide separated from the sand ?
Every che m istry class includes a few studeurs interested in subjects other than chemistry.
In recog ni tion of these nonchem ists, here arc a few p ro blems from ot her d iscipl ines.
Fro m geo log y: w har caused the deformat ion of the outer layers of the eart h an d th e
n msccluen t fo rmation of mo u n ta ins?
From a su bd ivision o f b iology, emb ryo logy : T he ne rve cells whi ch are d istr ibuted
throughout the bod y o f an an imal were o rigi na ll y, in the ver y yo u ng embr yo, all collected
together in one place. D ur ing th e su bsequen t gro wth o f th is em bryo, man y of these cells
left the site of their origi n and mi grated to remo te places in th e body, where they gr ew
into fu nct io ning cells.
What fac tors in it iated t his m igration? \\'h at di rected the m igr a tory cells to certa in
specific locat ion s? W hat was thei r mod e o f locom ot ion?
It is remar kable to realize t hat o nly lOO yea rs ago almost every q uestion listed in th is
ma n ua l as an exerci se for th c stude nt (ami many ot he rs, no t l isted , for wh ich the answers
are now fa irly well esta blished ) would have been p ut in t he list in th is part of th e m anual.
At some fut u re t ime t he an swers to the question s now listed here will be rea so na bly well
established and ot her quest ions not as ye t even co nce ived (!) will ta ke thei r place in a list
such as th is one.
Yo ur duty and pleasure, as a scien tist , will be to move q uest ions from the u nsolved li st
t he solved list (and occasiona lly back aga in ). Yo u will learn to note with awe th at for
e' "ery question re moved from the list o f un solved problem s two or three will arise to take
its place. A nd yct, for all this. o u r knowled ge of what is true gets closer and closer to T r u th ,
a nd th is is thc wonder of wonders.
to
77
TO THE STUDENT WHO HAS FINISHED THIS COU RSE
Nex t year anot her grou p of beginners will face the same tasks th at yo u faced th is year.
the tasks that you have mel an d solved . And ju vt as you did , th ey will ask th e upperclassmen
to help them solve their problem s.
:"\0 o ne would. for a moment, sugg est that this int erchange of ideas be tween beginning
and advanced stu den ts be st ifled. Especiall y in these t ime s of large enroll men ts and reacher
sho r tage . t he instruct ive aid furn ish ed by the u pperclassmen is mo st welc ome. H owever no
one wou ld want to prc\'cllt next year's begin ni ng students from lea rn ing all they ca n, and
im p ro per assista nce by th e upperclassmen ca n be harm ful.
So when a new stu den t asks yo u for hel p in figu ri ng out a solut ion to h is proble m, be
careful. IJl' ve ry care tnl, ho w you hel p h im . A bove all do not ans wer h is q uest ions b lu n tl y
and direc tl y. Mak e th e begin ni ng studc u t gct th e answer himself. \ Vhen he asks a qu est ion
of yOll, instead of ans wering it with a d irect sta te me nt , ask a q ue st ion of you r own that is
rel at ed to th e answer he seeks- and do n't make it a too-clo sel y rel ated q u estio n, either. Try
to ask h im qu estions wh ich, when he an swers them , will bring hi m o ne sma ll step closer to
the sol ut ion of his problem . A nd obvi ously. if he d ocs not know the answer to yo u r questi on ,
d o not answer it for him . Let it ha ng. telling h im on ly where he can find the answer, and
don 't be too speci fic.
It takes rea l sk ill to ask q uesti o ns in a '\'ar whic h will be of most hel p to the heginn ing
st udent. Yo u will proba b ly not do a perfect job . but try to do th e best YOli can. R eme m be r
the es...cu ria l pri nciple : Answer the <Ille..t ion of th e beginning student wit h a quest ion of
you r ow n, related to the ans wer h e seeks; not with a d irect and dear ..tatem cnt.
The inst ru cto rs, who ha ve some ex perience in teaching. will kn o w wh en it is best to
break th is rule. So do no t be di sma yed if they seem to di sregard the above precepts.
Above all, be su re that yo u do not take away from these n ew st ud en ts th e fun YOll had ,
the ex ulta tion you ex pe r ienced , when yOll ded uced the sol ut ion to you r prob lems b y
yourself.
78
HOW TO BECOME A CHEMIST
From yo ur use of this ma n ual you have acquired a b ro ad notion of why a person becomes a ch em ist an d h ow, after he is fu ll y trained , he works as a ch em ist. Bu t so me ad d it ion al aspects of the q u estion "Wha t i" a chem ist?" remain to be d iscussed . W e sha ll consider two po ints which pertain to the Fu tu re: first, wha t is req u ir ed in order to become a
perso n ,.. . hom o th ers will call a chem ist ; an d seco nd, wh at still remains to be accomplish ed
before such a person can really consider h imself a ch emist. Th is secon d topic \.. . ill be
d iscussed in te r ms of two d ifferent asp ect s, th e chem ist as a p roblem solver an d chemistr y
as a profession .
Let U s co nsi d er the first topic, the tranung to be received by a st ud en t major in g in
chem istr y. T he b ull etin or cat al og o f yo ur ins t itution lists the co urses to be taken and
br iefly d escr ibes thc co nten ts of each course. You alread y know that to receive a degree in
chemistry you w ill be required, in add ition to courses in ch emistry, to enroll in severa l
courses in ma themat ics and physics, in English , in a foreign langua ge , an d even in other
liberal arts cou rses.
T he reasons for the science an d mathematics req uirements and t hose of En glish are
d ea r en ough lo the stu dent who has used this manual. An d sin ce scientists in o ther co u n tr ies oft en descr ibe th eir work in th e ir ow n langu age, th e need for pro ficiency in at least
one fore ign langu age is clear. But wh y arc co urses in p h iloso ph y, or hi sto r y, or economics,
or music app reciat io n, or o ther, sim ilar non-science-rela ted su bjec ts requ ired?
T h is is not an easy questio n to answe r, but p er haps it can b est be answered b ri efly
ap posit ion. A ma n is a ch em ist ; a ch emist is not necessarily a man. T ha t is, in ord er
to act as a ma n sho u ld act, to be wh at a man sho u ld be, to th in k as a man shou ld th ink , it
is necessary to k no w more tha n jus t che m istry. Co nside r th is, can you read a newspaper or
magazin e, an d pro fit from such read in g , if yo u ha ve on ly a knowledge of ch em istr y? \V ho
could enjoy a piece of po pu lar or classical music by relying solel y o n h is knowledge of
ma th emat ics? Can train ing in p h ysics, alo ne, h el p you learn wh o yo u arc? \ Vill your
knowledge o f scien ce suffice to answer the q u estion , "\ Vhy am I ?" Clear ly, the h u man it ies
arc esse n tial.
by
a ll
I n an immediate pract ical sense, ho wever, students who hope to major in chemistry
will be in terested in the ch emi cal side of the educat iona l process. Curricula d iffer from
school to SLilOO!' It is no t possible to say that certai n courses will be ta ken in the Sophomore
year, ot hers in the foll owi n g year , an d still others as a Sen io r. Some t ime before gradu at ion
the chemistry maj or tak es a cou rse in an alyt ical chemistr y. You already know a bi t abou t
th is subject. I n special cases yo u can even no w te ll ho w to d etermine if a cer tain su bstance
is p resclll in a sam p le an d, if so, how mu ch of it is p resen t. From yo ur Future st ud ies in
this subjec t you will lear n how to do th is better, more accuratel y, marc rapidly, with an
ordered kno wledge of the su bje ct mauer. You will learn more abo ut why certain su bstances
react in partic u lar ways an d h ow to usc thi s knowledge to yield in form atio n ab ou t the
com position of mat erial s. A n alytical chemistry is the single bran ch of chemistry u po n wh ich
all ot her branches depend.
79
You no w kno w some thing about the fiel d of st udy called organ ic chemistr y. By
fu rt he r stu di es in this su bject you will learn mo re about the electron pair bo nds which hold
ato ms toge ther in molecule s. Yo u will learn about man y new kind s of organ ic compou nds ,
amides, mcrcap ta ns, thi o-ethers, alpha am ino acids, an d severa l othe rs. You will learn how
these su bstances are pre pared fro m simple r co mpou nds, how they react with each other
an d with d ifferent ki nd s of inorganic re agelll s, and wh y these reacti ons occu r. You will
learn how to pr edict th at a cert a in react ion will, or will no t take place, an d wha t the
prod ucts of the reaction will be, if th e reaction docs occur. Xlany studen ts find that orga nic
chem istry is extremely interesting and spend a lifet ime st udying this su bject.
Some o f the proble ms in th is manual have been selected fr om the field of ph ysical
che m istry : th e lower ing- of the freezi ng point of wat er by the add ition of a solute, th e effect
of temperature on the rate at which a reaction p roceeds, t he ability of a b u ffer sol ut io n to
resist chan ges in jJH, the value of R , th e rel at ions h ip be tween th e vapor pressure of a liq u id
and its tem peratu re, an d many others. I n a for mal co urse in physical che m istr y you will
learn how to ap ply conce pt s learn ed in p hysics an d mathemat ics to obtain a fu ller u nderstand ing of these pheno me na. T hose who like p hysical chemistry define it as the branch of
che m istry wh ich includes all thin gs; o thers d efine it as the che m istry of mathemat ics.
Often a cou rse in advanced inorgani c chem istry is part o f the che mistry maj or curricuh un . I n this co u rse you will learn more about the period ic ta ble, how to use it, wh y the
elements are arra nged in groups an d ser ies. Yo u wi ll learn about the uses and pro pe rties
of clem ents whic h were not stud ied , or only briefly so, in the in trod uctory co u rse , an d why
these clem en ts have these properties. Although ino rga nic chem istry is the oldes t branch of
chem istry, it is today probably the most import ant an d the fastest growing.
Yo u ma y also learn how to ap ply the knowled ge gai ned in your p hysical che m istry
course to a more detai led study of analyt ical che m istry. O r per haps you wi ll learn ma rc
abo u t organ ic chemistry in a second, adva nced cou rse in the field. O r you may be able to
choose a course in b iochem istr y. In this su bject a knowledge of che m istry, primarily p h ysical
and orga n ic chem istry, is enriche d by stu d ying its ap plica t ion to che m ical p rocesses occurring in living tissues . Lastl y, yo u ma y wish to work 011 a re al re searc h problem; in many
u nd ergr ad uate schools this is po ssible. Such a st udy is almost always ver y rewarding.
T hese, then, are the usual cou rses in che mi str y. T hose who are able to undertake this
regi men, and it is cha lle nging, make no m istake, will fi nd it worth the effort required .
Studen ts wh o are pa rtic ularl y successful sho uld cons ide r the de sira bi lity of further st udy
beyond the baccala ureate d egree- in grad uate 5d 1OOI.
T he ma jority o f studen ts who attend grad ua te school do so at no expense. T hey are
hired as gra d uate assistants an d work as supervisors of elemen tar y la borator ies, o r grade
exam inat io n papers, or assume other duties . Fo r thi s servi ce they receive pay su lri'cicnt
to meet their ex pe nses. A few of the ver y Lest stude n ts rec eive grad ua te fellowsh ips . A
gr ad ua te fellow is usua lly paid a bit mo re generously tha n a grad uate assistant but, even
better, he do cs no work in re tu rn an d can d evote full time to h is stud ies.
Two maj or cr iteria are used by the gra d ua te school in sele ctin g successfu l applicants,
the record of the stude nt's grades and the statemen ts in letters of reco mmend ati on written
80
by the applica nt' s u nd ergraduate pro fessors. O f th e two , a good grade record is the most
important. I n the first place, if t hi s record is unsatisfactory , a favorable letter of recommendat ion will not be written. Second ly, the record of grades already earned by the
applicant is o bv ious ly the best objective ind icat ion of success in grad uate school. Students
with grades that are consistently above ave rage, with at least a few outstanding grades in
science or mathemat ics, can expect to recei ve favora ble action by t he graduate school of their
cho ice.
Some student s elect to proceed directly toward the h igh est academic goal, a Ph .n.
degr ee . O th ers elect to try for a Master's deg ree. O ne ma y attem pt ei th er path ; it is not
necessary to first obtain a Master 's degree before beginning stud ies for the Docto rate altho ug h this can, of course, be do ne.
Master's de gre e students be gin their thes is wor k ra ther ea rly , wit h in a few mont hs after
arriving at gr ad ua te school. I n most schoo ls, whe n the required course work is completed,
proficiency in a foreign language demonstr at ed , and the thesis wor k almost completed , th e
Xl aster's degr ee cand ida te is g iven a ri gorous exa minat ion over th e entire field of chemi stry.
Upo n passing th is examinat io n an d u pon fi ni sh ing h is thes is work, th e stu dent can be
assured that he will recei ve hi s degree.
For the Doctorate candidate the path is more d ifficult . His required course work is
more extensive a nd h is th esis work more demand ing. H e must demonstrate proficiency in
two foreign lan guages and h is examination on the en t ire field of chem istry is much more
compre hensive, usu all y including bot h ora l and written po rtions . ' The Docto ral candidate
mu st also pro\'c that he is competent in the field he selected for h is thesis work. I n many
ca...es th is proo f cons ists of a demonstrat ion that the ca nd idate kn ows mo re about hi s own
t he...is wor k th an any o ther living person . Th e sacrifices req ui red , hard t houg h they are,
and man y, are worth t he result, te n tim es over. There are few rewards given to any ma n
which exceed the on e expressed by the sym bo ls ·" Ph.D."
8 I
SERENDIPITY, THE SECRET OF SUCCESS
I n this m anual two po int s have been em p ha sized : Che m ist r y is fun, but you must
think in order 1O en joy it. T hese two points ar c o f p r im ary im po r ta nce to a beg in ner in
ch emistry. Hut there is a thi r d poi n t wh ich shou ld also be ment ioned , on e wh ich will becom e im po rtant to yo u when yo u becom e a trai ned che m ist a few years from now . This
poi ur ca n be ex pressed by the word " serendipi ty: ' Loo sel y defin ed , sere nd ipity means t he
a bi lity to profit from th e u nexpecte d .
Al though it m ay not have seem ed 50 at the t ime. t he pro blem s u sed in this manual wer e
sim ple. T hat is, the answers which the p ro ficient stud ent ob tained were the answers wh ich
were ex pec ted . If the proficient student mad e no m ista kes, the ans wer he o bta ined co uld
have been predi cted in adva nce b y any ot he r profi cient st ude n t. H o wever , the pr oblems
that will co n fro nt the trai ned chemist arc not always th is simple ; o ften the r esul ts cannot
be p red icted in ad va nce. Even though the che m ist may make no m ista kes as he works on a
prob lem , it is not always possib le to for esee the re sul t he wi ll o bta in .
\ Vh y is t h is so? I n or der to reach t he su bject of chem ist ry to th e be gin ner it is necessar y
care fu lly to select p roblems wit h know n answers . O therwise, it wo u ld be d ifficult, if not
im possible, to help the begi n ner learn th e m ateria l he m ust learn in order to becom e a
trai ned che m ist. H o wever , there are m any m an y th ings wh ich arc not yet known a bout
che m ist ry an d th ese arc the yery things wh ich the tra ined chemist st ud ies, Since th e tra ined
chem ist works in an u n known re gio n , it is to be expected th at ma ny of h is problems will
h ave u nexpecte d answers,
H owever, in or der to begin wo r k o n an y problem, whethe r it has an answer wh ich is
know n or u n known , it is necessar y tha t t he chem ist have so me well -tho ught-out id eas co ncern ing th e p roblem . It is certain that no o ne ever solved a di fficult problem b y tackl in g
it ra sh ly. Bu t m an y m an y workers have missed golden opport un ities b y cli ngi ng to the ir p re ·
li m in ar y ideas too ten acio usly. Cavendi sh anal yzed the consti t ucm s of th e at m os phe re and
fo un d th at h is percen tages d id not qui te add lip to 100 pe r ce nt . H e att r ibu ted thi s d is,
cre pancy to h is prelim in ary n ot ions that the atmosph ere co u ld be com posed on ly o f n itrogell. ox ygen , wa te r \'a po r, and carbo n d iox ide, and 10 the su p posed fact th at h is an alyses
were sligh tly in error. H e m issed d iscoveri ng th e inert gases which we kn o w, today, to be
also pre sen t. O n t he o ther ha nd , as Mendc lccv de vised hi s period ic ta b le , h e not iced tha t it
was ne cessar y to a ba ndon h is o riginal ide a that the elemen ts sh ou ld be arranged cousccut ivclv in ad jacent positions in the order of t heir increasing atom ic we igh ts, \\'e ho nor h im
a ~ t he di scoverer of th e periodic table , o ne of the most sig n ifican t achievemen ts of th e h u m an
int el lect . Mendelccv in deed began with a preconce ived notio n of thc answer he expect ed ,
but when h e re cogni zed that h is expect ed answer was mistak en . he seized u po n the u nexpected re su lt tha t he d id find and estab li sh ed a new princi pl e. Bccquercl o bserved that in
on e of hi s ex periments a photo gra ph ic p lat e was unexpect edl y fogged . H e had begu n wit h
an elaborate, logica l p lan to stu d y th e phenom eno n of lut u iucwc ucc but his res ults did not
fit the plan at all. Others had stu d ied the sam e phenomenon (the ir n am es arc u nk nown
toda y) an d h ad ob-cr vcd sim ilar un expe cted result s which they di sm issed as u n important
beca use the se resu lt s d id no t co n form to what they had ex pected. Bccq uc rcl d ropped h is
82
preconcei ved id eas an d pu rsued the cau se of th e u n ex pected resu lt. H e discovered the
phenome non of rad ioact ivi ty.
T he li st is end less. Irvin g Langm u ir, on e of t he outstanding scientists of this cemury,
att r ib uted m ost of h is d iscoveries LO sere nd ip ity. The l igh t b y wh ich you read , the au tomobi le in wh ich you r id e (to men t ion two a pplications of h is work) wo ul d no t be as we have
th em to da y if Langmu ir had not rea lized that som e unexpected results which he ob ta ined
d uring h is research work in d icated t hat h is previo u s ideas about certain p henom ena were
wro ng. O th ers had not iced th e sam e pe cu liarities in their work b u t had d ism issed th cm as
un im portan t. T h cy fa iled to see t he implicat io ns of the unexpected.
Each of these wo rkers, Caven di sh , Xlcudclecv, Becq uercl , Langm uir, an d all t he others,
wh ethe r th ey p racticed serend ip ity or not, all bega n with a p lan ned expe r imen t, wi th a
p re co nceive d notion of wha t to expcct for a n a nswer. And, J uring th e course of th eir wo r k,
they n oticed a sm all or large d iscr epancy b etween wha t di d happen and what wa s expect ed.
Sonic att r ib u ted th e unexpected r esu lt to a m ista ke in the la boratory wor k and d ism issed the
mat ter as u n import an t. Ot hers, suc h as Bccqucrc l, Xl cndc lccv , an d Langm u ir, a ttributed
the u nexpected resu lt to a m istake in their original ideas, altered the se ideas, a nd di scovered
a new con cep t.
Now all carefu l workers who come across a n un expe cted r esu lt will first ch eck the ir
laboratory work be cause the y know from bitte r experience how ea sy it is to mak e a mista ke
in th e la borato r y. And u su all y the unexpected resu lt is in fact due to an error in la bor ator y
tech n iq ue. U pon ca refu l repetit ion of th e la borator y p roced ure, the u nex pected result
d ocs no t occu r agai n and th e pre co nceived ide as are ther efore d et erm ined to be consiste nt.
But occasiona ll y t he u nexpect ed result r eoccurs, an d the worker th en h as a choice o f di sm issing t he unexpected resu lt as an uni mport an t happenstance or of accept ing it as real an d
pu rsu in g it fu rth er.
T he ch oic e selected, to p ursu e or to d ism iss, probab ly d e pends largel y u pon t he m ental
alti tu de o f the scie n t ist toward hi s wo r k. Certain ly those who reall y enjoy their work are
more l ikel y to see the un expect ed re su lt as a ch all en ge 10 be overcome : whe reas the wor ker
who v iews h is ta sk o nly as a daily occupa ti on to be performed in a rou tin e ma n ne r is less
li kel y to be stim u la ted by an u n ex pected resul t. H e will be in cl ined to d ismiss the u nex pected as unim portant eve n though re peated experimen ts, if in deed h e h as bothered
to carry out a re petition , show t hat the u nex pect ed resu lt is real.
T he concl usi on is o bviou s. T o p ractice sere n d ip ity, it is de sira ble th at you find your
work in chemistry en joya b le, and it has been th e aim of th is la borato r y man ua l to foster
th is atti tude.
83
THE RESPONSIBILITIES OF THE CHEMIST
Man y who read th is w ill beco me ch emists, an d it is for them , espe cially, th at the d iscussion is inte nded. BU l these co nsidera t ions arc also of im p ortance to those re aders who
will choose oth er vocat io ns: for tod ay, m orc t han eyer before, scie nce affect s c\"er yonc.
T h ese o thers sh ou ld know th at chemists han: an ob ligat ion towar d the m, and sho u ld know
just wh at th is ob ligat io n is.
A d etailed sta tem en t o f the eth ics of the chemical pro fession , fo rm all y accepted by
most chem ists, d ocs no t ex ist. BU l LInaugh the year s an in form al unde rstandi ng o f the
respon sibi lit ies of the chem ist ha s evolved . W hat fol lows is the a uthor 's in terpr etat ion of
that in formal cod e , with special em p hasis 0 11 those par ts a pplyi ng to the inex per ienced
chem ist. Mu ch that per tains to the matur e professiona l ch em ist h as been om itted .
'\'e can be gin by asking the q ues tion : ' Vha t do es it mean to b e a good chemi st? T he
an swe r is twofold . A good chemi st is on e who kn ows h is chem istr y, wh o ca n ex p ress h im sel f wit h pro ficie ncy in writing and spea ki ng, and who see ks to increa se hi s knowledge o f
chem istry by co nt in ued study. A cousc icnr ious ch em ist cannot SlOp lear ning upon gr ad u ation , H e m ust 1'0110\\' a plan n ed cun- icu lu m of continued st ud y th ro ughou t his life. (O nce
begu n , th is is n ot so ard uous a task as it m ay appear to bc .)
T he second par t o f the answer is a li tt le mo r e d iffic ult to m easure u p to: A goo d ch emi st
is one who fu lfills his respo nsib ilit ies- an d h e has m:lIIY.
' Ve n eed n ot discu ss h er e the r esponsib il ities imposed b y Cod upo n eYery m em ber
of the human r ace : T o try to l ive in acco rd wi th the ten co mmandments and thc eight
beat itu des. Nor is ou r concer n with the d ut y of eye r y profession al man to carefu lly form
his ow n opinion on the curren t pro blems o f society, to properl y in fluence the o p in ions of
othe rs, to fu llill civ ic d u tie s, to im prove h is kno wledge 0 1" m att ers not d irectly r elate d 10
h is own field b y a pla n ned program of self -stu dy , and so Oil, T h ese duties ar c obviously
requi re d o f all.
O u r co ncern is with those respon sib il ities whi ch arc d irectly conn ected with the work
of a chem ist as a chemist. T hey can bc consi de red u nder three aspects: r esponsib ility to
society; responsib ility to an em plo yer ; re sponsib ilit y to O Il C's fe llow wo r ke rs.
III acquiri ng an educat ion , c\'cr yon c is indeb ted to h is p redecessors for th ei r contribu tions toward an u nd er stand ing of nat ure and to hi s contemporaries for their insp ir at ion
and enco u ra ge ment. Fr om Ari stot le th ro ugh Al bcr tu s Xlagu us and Lavo isier , to P lanck
an d Einstein , to ment io n on ly a few, from the immed iate fam ily, fro m tea ch ers and friend s
and Illan y o thers, have come contri butio ns ma k ing it possib le for you l O b ecom e an educated
ma n . To these benefactors an obligation is dearly owed .
Chem ise, can pay this debt in m an y ways. So me will set o u t purposely to co ntr ibute
new kn owledge. T hese re search wor ke rs arc obl igated to be o bjec t in in t he p u rsuit and
interpre ta ti on of th eir findings, and not to distor t the resu lt s of these ex peri me nts to suit
their OW II ends and prejudices.
Some will use the know ledge they h an
84
gained b y transm itting it to others, T h is
grou p. whic h in cl udes teach ers an d o th ers wh o com e before the public wit h infor m at io n .
is ob liged to seck and transmi t new kno wled ge th at is d eveloped by th e r esea rche r , and to
avoid teaching false in for m at io n . Chem ists must welcome opport u ni ti es to speak p u blicly
about the ir profession , to help ot hers u nd erstand what ch emi str y is an d what che m ists do .
Other chemist s will go into in d ustr y. T h is group has a moral res ponsib ility to !'>ee
that their work is used for th e benefit. and not the det ri ment , o f mank ind . T hey m ust
"su p port and cncou rage the leg-al and eth ica l u se of chem istry. and o ppo<,e its improper usc .
All chem ists. of co u rse, are com m itted to expQ<,c fra u d and er ro r whi ch may n ot be
apparcnt to the genera l p u blic. but which their train in g ena bles them to recognize. I n
such cases, ex pe r ien ced chem ists sho u ld be consulted be fore pu b lic act ion is tak en .
The chem ist ha s a dearl y defined responsibi lity to h is emplo yer. H e m ust contribute.
and he must be loyal. O bviously, th e chem ist-employee will he in d ustri ous , see king to do
more than th e min imum work he is assigned. H e is a lso obliga ted to learn about his em ploycr'v prot-esses. hi s p lans for the Futu re , his prob lems. admin istrat ive proced ures . and
particu lar way of doing bu siness, in order to cont r ib u te effect ively and efficie n tl y to the
welfare of hi .. emplo yer.
Fu rth er. he will hold the in forma tio n concern ing h is emp lo yer's private p lan s and
technica l work in confide nce. Since he ha s learned t hese thing.. as a n agent o f h is employer.
he has no ri ght . excep t b y proper legal professes, to d ivu lge t his informat io n to others who
wo u ld use it to th e d isadva ntage o f hi s employer. Th is o bliga tion ho lds even after h is
em p loyment has been termi nated . although it i s certa in ly proper to u sc all such pr ivate
information , leg iti matel y acq u ire d, as pa rt of h is per sonal p ro fessiona l exper ien ce. I n addi t ion , it is u nct hica l to with hold , for fu tu re perso nal be nefit , au idea of one 's own th at the
em ployer llIay ri gh tfull y ex peel to be used to hi s ad van tage . O f co urse, the ch em ist has
th e r igh t to usc, for h is person al gain, any infor m ation or id ea he has leg itimately acq u ire d
b u t wh ich l ies ou tside th c ter ms of the em plo yme nt con tract . It is p r u den t, however, to
LJc con serva tive in these ma tt ers .
w hen . d ur ing the da ily work, d ifferences o f o pin ion ar-ise b et ween the ch em ist and
h is emplo yer, the ch em ist will try to re solve t he m pat ien tly a nd tactf u ll y. H e will , in effect,
seek the welfare of hi s employer as th ough it were h is o wn .
T he re spo nsibi lity of a go od chemist to ward his fel low wor kers can be su m m ed up in
1I1e\C words: rc spect , loyalt y. an d contri b u t ion. Ever y man i~ all ind ivid ual and is en titl ed
10 the respect o f oth er s. T he inexperienced chemist, in part icu lar, w ill listen to th e suggcstions o f h is fell o w worke rs , whet he r they be 0 11 chem ica l p roblem s or rel ated to ot her
subjects , whether they be voiced by a chem ist or by a non -chem ist.
T h e ch em ist is solic itous o f the ph ysical welfa re o f hi s fello w workers and follows safe
practiccs in the laboratory. H e ex presscs h is consid cration for others b y keep in g h is work
' p:KC neat , hy encou ragin g h i.. su bor d ina tes to improve th em selves, and b y refra in ing from
be littl ing gossip COl Kerning h is su bor d inates. su pe rvisors. and Fellow workers. H e does no t
tak e unfai r ad va ntage of ot hers in seek in g h i.. own advancement . I n shor t , he recognizes
hi s responsibil ity to promote ph ysical and social harmon y in the organization of which
he is a part.
85
T he chemist ,su p port s h is professiona l society 'b y mcmbcrship , b y part icipation at
meeti ngs, an d by ac tivit y in co nun iu ces and ot her functioning bod ies. H e recogn izes h is
obligat ion, whe n commitmen ts to his employe r wi ll allow, to p u bl ish the re sults of h is
scienti fic work in the tech n ical journals or at me etings of his socie ty, and no t elsewhere.
In such p ublicat ions, he is alwa ys careful to g ive credi ts to ot hers who have contribu ted to
the success of hi s work .
Above all else, he never assum es cred it for a d iscover y tha t p roperly belongs to an other
scien t ist. T o acce p t un due credit is desp icabl e, for it means that he has sto len , not fo r
mo neta ry ga in (which is bad enough) , but for thc appro bation of o thers (wh ich is far worse} .
The pract ice of chem istry, the n , is a profession . And the d ist in ctive character ist ic o f
a pro fession is its ob ligat ion to serve. Che mists, the refore, are ste ward s; they are cus tod ians
and seekers o f kn o wledge ; they arc servan ts o f h u man ity. Beca use they are pro fessional
men , they will fin d a certain joy ill d oing more than the minimu m req u ired in their rel atio nships wit h socie ty, with their employer , an d wi th their fellow scie nt ists.
86
ADMINISTRATION OF THE LABORATORY
Reagents a nd special items
D ue to the nature of the work p rescr ibed in th is manual it is no t possible LO Lite a
complete ca ta log of materia l needed d u r ing th e year. H owever, ex per ience h as shown that
the ma teri al listed b elow will su ffice to m eet all bu t th e un u sual r eq uests o f th e students.
Add it ional ne eds can u sually be met from the ord inary stocks ob ta ina b le from the la borato r y
. stoc k room or from local h ard war e, f,'Toccry, an d oth er stor es.
S O LI n R EAGE:'\TS
Aga r agar
Al um ina ; act ivated AL,l0 :\ ' xH:: O
Aluminum ,\ 1; fo il
Al uminum AI; gran ular, 8 mesh
Alu mi num AI; tu rn ings
Aluminum chlori de; anhyd rous AICI;"!
Alumi num ch lori de AIC I:1 • GH :: O
Al uminum sul fate .-\ ldS O~h · 18H::O
Ammoni um acetate C H:I C O ON H~
Ammoni um carbona te ( N H ~ )2 CO;l
Ammonium ch lo r ide X H~ C I
Ammo n ium d ichrom at e ( N H ~ h C r :: O j
Am monium d isulfa tohe xnaquoferra te (I I)
(X I I ~ h [Fe(SO ~ h (0 H 2)fl]
Am mon ium nitrate N I I..X O:1
Ammoni um sulfate (N H ~hS O ~
Anil ine hyd roch loride C'l H .; XH 2 • H CI
An iline yellow dye
Ant imo ny Sb
An tim o ny trich lor ide ShCI;\
Ar senic (II I) ox ide As..O u
Asbestos fiber , acicl washed
Azoxyben-enc C,;H ;;(:\O:\)C,;H .;
Bariu m hyd rox ide Ba (O H h ' 8H 2 0
Bar ium peroxide BaO ::
Hen- idc ne ( X I I :: C ,; H~h
Bismu th (II I) ch lor ide B i Cl ;~
Bo ra x, n ude; if not ava ila ble, conta mi na te
sodium tet ra borate with a litt le sodi um
car hona te a nd ca lcium car bo na te to simulate crude ma ter ia l.
Bo ric aci d II ::BO :\
Cak ium Ca; lumps, pelle ts or tu rni ngs
Caki um carbide CaC::; in sealed contai ner
Calcium chloride Cael::; a nhydrous
Ca lcium h yd rox ide Ca (O Hh
Cal cium pho sp hide Ca;~ P ::; in sealed conta iner
Calcium su lfa te CaSO .. • y:! H ::O
Ca lcium sulfate CaSO .. • 2H::O
Ca r bon C; cha rcoa l, block
Ca rbo n C; cha r coa l. powdered
Ca rbo n C; graphi te powde r
Carbo n d iox id e CO 2 ; solid ; D ry Ice
Cation exc hange re sin; Dowcx 50, h ydrogen
for m
Cation exc hange resin ; J'er rnutit Q
Charcoal: act iva ted (Da rco brand)
Chrom ium (I I I) ch lorid e c-ci, · 6H 20
Ch ro mi um (I II ) oxide Cr::O:\
Citric acid
(CO O H)C H ,C-(O H) (CO O H)-C Il,
(CO O H)
Coba lt (II ) ch loride CoCI:: · 6H ::0
Cobalt (II) nitra te CO(NO ;lh ' 6 H::0
Co pper Cu: sho t, #8
Copper Cu: strip, ca. I em by 5 cm
Cop per e u; wire, har e, # 18
Coppe r (II) ch loride CuCI:: · 2H :: O
Copper (II) n itra te Cu(X O:1h ' 3H:: O
Copper (II) ox ide Cc O
Co pper (II ) su lfa te C uS O ~ ' 5H:: 0
Egg a lbumin; d ried
Ferr ic ammon ium citra te. com mon nam e for
im pure { X H~h ' ~ Fe[(COOh C 3H ..O H h ~
Gela tine
D-Gl ucose CGH12 0 fl
Iodine I::
Iro n Fe; filings
Iro n Fe; wire , hare. #18
Iron Fe; wire , ha re, #2,1
Iro n (II) chl or ide FeCI:: ' 4H 2 0
I ron (II I) chlo r ide FezC I,• • 12H z O
Iron (III) n itrate J.'e (N O :.b · 9H ::0
Iro n (II I) oxide Fe z 0 3
Iro n (II ) su lfate FeS O ~ ' 7H:: O
Iro n (II) sulfide FeS
Lead Pb : shot . # 8
Lead Ph ; strip, ca. I em by 5 em
Lead (II) aceta te (CH ;\COO):: Pb · 3H 2 0
Lead (I I) n itrate I' b (N O :\)::
87
(contin ued )
Le ad (I V) ox ide P bO z
Le ad mono x id e PbO
Trilead tetro xide P b :\ O ~
Lith ium chlori de LiCI
:\fagnesiu m :\Ig; gra n ula r. 20 mesh
:\lagn 5i u m Mg; ribbo n
:\l agn 5 iu m carbona te :'o lgCO :!
:\Ianganese (II) ch loride :\l nClz • -l H 2 0
.:\ fanganese di o xide :\lnO z
Xla ngan ese (II) sulfa te M n SO ~ · H zO
Ma rble ch ip s im p ur e CaCO :!
" fercury (11) chlorid e HgCl z
:\Iercury (I I) ni trat e I lg(NO:I ) 2 • H 2 0
Na p h tha lene C l l1 l- l ~
fJ·N a p h tho l C1u H , O l-l
N ickel (II) n itra te Ni(N O :1h ' 6 H 2 0
Ni ckel (II) o xid e N iO
N icke l (II) sulfate Ni SO~ · 6 1-1 z0
Z. -t-Dinitro phe n yl h yd razine
C, OZh Clll-1 ;\ N I I N l l z
Oxalic add (CO O Hh ' 2 H zO
Pa ra ffin C. H . +z
Pheno l C" H ,..O H
Ph th a lic a n hydride C,; J I~ (C Oh O
Po tassiu m b rom id e KRr
Po tassium ca rbona te KzCD a • 1.5 H zO
Po ta ssiu m chlora te KCIO :!
Pot assium chlor ide KCI
Pot assiu m chroma te KzC rO..
Pot assium cya n ide KCX
Pota ssium d ich ro mat e K Z Cr 2D ,
Tri potassi um hexacyanofer rare
K:I[Fe (CN),,1
Soda lime; m ixt ure of 1'\aO Il a nd Ca (O Hh
Sodium ace ta te C H aC O O Na ' 31-1 2
Sod iu m perbora te. ~ aBO a ' 41-1 z0
Sodium tet ra bo ra te ~ a zn ~ O .· IOH z O
Sod ium b ro m id e Na Rr
Sodi u m ca rbonate Na: CO:1 ; a nhyd rous
Sod iu m car bo na te .....a: CO :\ • IOH zO
Sodi u m ch loride Na CI
Sod iu m d ichroma te Na 2Cr20 , . 211 2
Sodium h ydrogen su lfa te 1'\a IlSO .. • H 20
Sodi u m h yd ro xid e N aO H ; pe lle ts
Sodi um iod id e Na I
Sod ium nit ra te Na XO :1
Sod ium ni tr ite Nai\' O~
Sod iu m ox ala te ( CO O)~ ~ a ~
Sucrose, imp u re ; d ar k b ro wn cane sugar
Trisod ium phosp ha te
i\'a ;:PD j ' 1 2 H ~O
Sodium di hyd rogen phospha te
1\"a H:PO j ' H ~ O
Sod ium monohydrog en p hospha te
°
°
X a~ HP O ~ ' 7 H~ 0
Sodiu m po ta ssium tartrate
~aO OC(CH O H hCOO K
' 4H zO
Sodi u m pyrosul tire X a zS ~O :.
Sod ium sul fate 1\""250 ..
Sod ium su lfite Na 2SO :\
Sod ium thiosu lfa te N'a 2S20 :\ ' 5H 20
Starch . pota to
Steel woo l; # O()
Sucrose C 1 : 112 2 011 : ca ne suga r
Sud an red d ye
Su lfunil blue d ye
Su lfur S
T in Sn: gra n u lar, 30 mesh
Tin Sn: Illo s~y
Ti n ( II) ch lorid e SnCI 2 • ZJl: O
T ita n ium d io x ide T i0 2
Urea CO C:, H : )2
wood sp lin ts
Zinc In : gra n ula r. 30 me sh
Zin c I n; mo~sy
Zinc Zn; str ip. ca . I em by 5 ern
l in c car bo na te ZnCO a
Zinc ni trat e Zn(N O :1h · 611: 0
Zinc oxide l nD
Zinc sul fa te Z n SO ~ • 711:=0
'Tet rapota ssilim hcxacynno rriaq uoferra te
K ..[Fe (C N),,(1120):IJ
Pota ssium h yd ro x id e KO I-I ; pe lle ts
Pot a ssium iodate KIO ;\
Po ta ssium iodide KI
Po tassiu m n it ra te KX O :\
Po tassium permallga na te KMnO..
Potassium su lfa te K z SO ~
Po tassiu m th iocya na te KSC N
Resorcino l C" H j (O Jl h
Rock salt im p ure NaCI
Sal icylic add HO C,;l l j CO OH
S;lI1d impure SiO z
Silver nitra te Ag:'\ O ;1
Soa p. mi x ture of sodi um salts of fatty ac ids,
im p u re; fla kes or g ran ules
88
Solutions and liqu ids
N ote : I n those cases where the co ncentrat ions of solu tions are not specified in th is
man ual , solu tions of th e concentrations listed here should be used. I n those cases where
solut ion concentrations are speci fied, b ut differ from those listed here, the studen t is expec ted , as an exercise , to prepare his own solu tions eithe r b y d iluting a stoc k solu tio n or
by dissolvin g a weighed quan t ity o f solu te 1Il the proper amount of solvent.
T hese solut ion s shou ld be available,
la bora tory:
1Il
sets of bo n lcs, conve nien tly set ou t
Acetic acid C H ;\C O O H , 3-M
Acet ic acid C H :\CO O H . glac ia l
Ammonium hydroxide N H 40 H , 3·M
Ammonium h ydroxide
:\ H 4 0 H , cc nce nt ra red
H ydroch lor ic a cid H C I, 3·M
H yd ro ch lo ric acid H C I, concent rated
.\ (e thy l orange, 0.1% ; in d ro p p ing boule
T hese liqu ids sho uld be placed
III
1Il
the
Ninic acid H NO;\, 3·M
Xitric acid II NO :I , conce ntra ted
Phcnolpluhale in C ~O Il14 04' 0.1% : in d ropp ing: bottle . Di ssol ve I g in GOO m l of 95%
etha nol an d add ·!OO m l o f wat er
Sodi um h yd roxide NaO H , 3-M
Su lf uric' acid H 2S0 4, l.5 -M
Sulfuri c acid H ~ S0 4 ' concen trated
the hood :
,\ <etyl ch loride C H :\C OCI
Bro mi ne Br 2 : in d rop p ing bo tt le
Bro m in e wa ter; a sa t ura ted so lut ion o f Br z in
wa ter with a litt le ex cess Br2 in the bottle
lten zen e C nH ()
Be lllO}'1 ch lor id e C,JI ..,COC I
Carbon tetrachlorid e CC I4
C hlo ro for m C I IC I:1
Eth yl ether C ~ H ... O C ~H .-,
Fo rma ld eh yde . ca. 40'%
aqueous
T hese liq u id s sho uld be avai la ble from the side shelf:
Ace taldehyd e C H ;;C H O
Acetone C II: ;COCH :\
I/·,\ my l alc o ho l C..,1l 1 1 0 H
.·\ lu m in u tll chloride A ICI:\, 3-.\1
..Yluminum nitra te AI(:\ 0 ab . I-M
Am mon ium chl o ride ;,\H 4C I. 1·.\1
Ammonium oxala te (COOh(i\ H4):!, 0.25-M
Am mo n ium sulfate (i'\ H4b S04' 0.25·M
Am mon ium su lfid e (N H l):! S. 3·M
Am moni um th iocyanate " H 4SCN , 0.5-M
An ili ne C,;H ... N H~
Barium chl o ride BaCl :!, O.25·M
Bism u th ( III) xnrare B i ( :\O ;~ h , 0.2-M
Brom cresol green (ind ica tor), 0.05% ; in d ro pp ing: bo tt le
II-Btlly l aIr olm l C 4 H H O H
/I . But yl b ro m ide C 11 Br
4 i.
sec-Buty l bromide C 4 Hjl Br
Cadmium ch lor ide CdC I:! , 0.25-.\1
Ca lcium ch lori d e CaCI~ , 0.5·.\1
Collod ion U .S.P. so lutio n in et h er
Co p p er (II ) ch lo ride CuCI:!. I-M
Copper (II ) su lfa te Cu S0 4. 05 ·M
Eth yl a lcohol C:!H .-. O II , 95%
I , 2· Did lloroe tha ne C ll ~C IC H :!CI
(;I yfe ri ne C H ~OI IC H O HC H~O H
H yd ro ge n peroxide H ~O ~ , 10%
Iron (II I) ch lor ide FeC I;\, 0 .5·M
Kerosen e CH H n + ~ , impu re
Lead (II) ace tate (C H: ;COO h P b, 0.25-M
Lead (II) n it ra te Pb (l\'O:;b 0.25-M
xtagn csium ch lo ride ~ lgC I ~, O.25-M
:\la gll esi um ni tra te .\lg( i'\O:J2' I-M
.\fagn csiu m su lfa te .\lg S0 4• I·M
.\ bnganese (II ) su lfate MnS0 4, 0.25-M
.\lernlrY Hg: in bottle fitted with d ropper
.\l('rcm )' (I I) ch lori de HgCI :!, 0.25·M
.\ fernt ry ( II ) n itr a te H g{l\'O:lb I·M
,\le thyl alcohol C H:10 Il
X id ..el (II) chloride i\iCI 2 , 0.25-M
Nit robe nzene CG I-I .-.l\' O ~
O leic arid C ~ H I,C II: C HC, H 14C O O H
Par a ffin oil
Ph osph or ic acid H :I P0 4, (j-M
Po tassium bromide KBr, 1-,\1
Potassi um ch ro ma te K 2 Cr0 4 • 0.25-M
89
Sod ium o xala te (CO ONab O.25-M
Sod iu m silicate Na:! O. xSiO~; _10° Bc.,
weigh t r at io N at O to SiO :!, ca. 1: 3.25
Sodi u m sulfate N"a tS 0 4 , 0.5-11I
Stro n ti u m chlor id e S rCl~ , 0.25-M
T h ymol blue (indica to r), 0.05% : in d ro pping
Lottie
Tin (II) chlorid e SueL.! , 0.5·;\1
Toluen e CHII ;, CII;j
Turpent ine
Un iver sal Ind ica tor .. t
Vinegar (a 1% a ce tic acid solution lIlay be
subst it ut ed )
Zinc chl oride ZnCI :! , 3·M
Zin c su lfate ZnS0 4 , I-M
Po tassiu m dichroma te K ~Cr~O " O.S-At
T r tpo tasstu r u hexa cya noferra te
K ~ [Fe (C N ) ,;] , O.S-At
T e trapotassium hexacyanolerrate
K 4 [Fe (C N )l> J, 0.5-M
Po tassiu m h ydroxide KO H , 3·M
Po ta ssium iodid e KI , I-III
Po ta ssiu m perma ngana te KMn0 4 , 0.01·A1
Pot assium thio cya na te KSC"':, I-M
Isopro p yl alcohol C;\ H , O H
a- P ropy l alcoho l C;IH 'jOH
Silver n itra te Ag NO a , 0.5·11I
Sodi um chlo r ide NaC!, I-III
Sod ium fluo ride Na F, O.5·11I
Sodiu m hyd rog-en car bona te N a HCO;I' O.5-A!
Sodi um n itra te NaN O ;\, I-M
bromthymol blue
methyl red
phenolphtha lein
thymol blue
Dissolve in 100 ml of 95% ethanol. Add O.05·,\f Na O H um il green . Dilute to 200 nil with water.
Foster, L. S., and Or unrtest, I. J.. J. Chern. Ed uc., H , 274 ( I!J37).
.. 0.050 g
0.0 13 g
0.100 g
0.005 K
t
N ote : Due to h yd ro lysis, solut ions of some salts of the heavy metals will be clo ud y.
Addition of a few m illi liters of the proper acid (hyd ro chloric acid for chloride salts, for
exam ple) will repress the h ydrolysis and d ea r the solu tion.
Solutions of the lower valence states of some metals oxi di ze, on stand ing, to the hi gher
valence state. T hese solut ions should be fre shly pre pared (j ust befor e use) from sol ids of
kn own com position, or, if earl ier pre pa ration is necessar y, an exce ss of the metal itself put
in the bo ttom of th e bot tle and a li tt le excess of the correspondi ng acid added. (Such bottles
sho uld be stoppere d wit h one-hole rubber stoppe rs fi tt ed with a Bu nsen valve in the hole.)
Ca tch-a ll List
The eq ui pme nt issued to each student at th e begin nin g of the year suffices for most
of h is needs. Fo r practic al reasons, ho wever , not all nee ded equi pme nt can be placed in
his han ds for the ent ire year. O ften, a special piece of eq uipment is used only for a short
t ime ; or, d iffere nt st udents, from year to year, will request d ifferent items in the course
of wor k on the same problem ; or, the equipmen t ma y be too delica te to use witho ut dose
su pervision, too bulky to store in a small space, too costly to purcha se in large q uantities;
a nd so on .
It is recommen ded that th ese item s be ava ilable for use when needed :
Aitch-ru -ess cartrid ges (so urce of H 2 S, p ro priet a ry-ava ilable fro m laboratory su p ply
house)
Am met er s
Alli gator d ips (o b taine d from electro nics su pp ly hou se)
Asp irators (to fit water ta ps)
Ba lances (vario us capacities and sensi tivities)
Blanke t, fire smotheri ng
Blast burner
m o w pip es
Buch ner fu nne ls
90
O ffi ce sup p lies (erasers, gu m me d ta pe. p a per
di p s, ru bber bands. ruler, scissors, etc.)
Pe troleum j ell y (Vaseline )
pH m et er
pH test p ap er
Pi p et s (asso rted, fro m sm a ll sizes, fra ctional
m illi liters, I ml to 50 Illl)
P latin u m w ire, #24 su ggested
Pneuma tic troughs
Potassi u m iodid e-starch test pa per
Candles
Centr ifuge. and centr ifuge tu b es
C lo th swa tches (small , ca . 5 r ill square ; prefera hly wh it e. Ace tate r ayo n , cotton , d acro n ,
n ylon , silk, \1'001 , etc.)
Copper w ire, ins u la te d , # 18 sugges ted
Cork bo rers (asso rt ed sizes; and sharpener)
Cotton , abso rb ent
Desicca to rs
D irect current source (p ref era b ly var iab le. 0
10 10 or 15 vol ts, with attached voltmeter
and a m me ter)
Electri c ho t p la tes
Em ery doth (as sorted gra des, coa r se to fine )
Filter paper
(asso rt ed porosities and d iam eters)
Fir e ex tingu ish ers, va r io us types
Fir st a id cab ine t, well -stoc ked
Hot air dr yin g d evice
G la ss \1' 0 0 1
Cooch cru cib les, with pla te s
Graph ite rods (p en cil "lead " o r anode Irom
dry cell)
le e, cr ushed
In ca ndescen t lights, typ e 46 or 47, 6 to 8 volts
(a nd socket to fit)
Iron dishe s (assorted sizes and sha pes)
Labels, g um m ed p aper
Menur)' ba romet er (o r a nero id if a m ercury
barometer is not ava ilable)
Meter sticks
::'\ails, 3d fm ish ing
X ich rorne wire. # 18 sugges ted
l'ycnomcters
P yrex or Kim ax tubing (assorted diamete rs, 3
m m to 15 m m )
R efrigerator (used infreq ue n tly, n eed n ot be
imm ed iately accessible)
R u b ber halloons (sm all sizes)
Safety shower (p u ll lan yard to ac tua te]
Speci fic gra vity bottles
Stopcock gre ase
Stop wa tch
Stra ight p ins
String
Th read
" Tin" cans (assorted sizes a nd shapes)
Vacuum tub e voltmeter
Vacuum p um p . mech an ica l
Voltme ters
Volumetr ic flasks (va r io us sizes)
\ Vo rksh o p equipment and su p p lies (fro m
hammer. n ai ls, saw, screw d ri ver-through
portab le d ri ll-to ba nd saw a n d la th e, the
more complete the be tt er
Memora nda for the First Few Laboratory Period s
THt: FIRST
i-zaron :
I. Assign in d ivid ua l locker or d rawer space to the students.
2. Demonstrate the use of safety dev ices-fire ex tingu isher, fire blan ket . safety shower.
etc.
3. Emphasize the im porta nce of first aid treat ment, even for m mor accidents.
4. Describe the procedure followed whe n corrosive l iq ui ds are spille d on the cloth ing
or skin, in particular, the eyes.
5. Advise studen ts how to obtain ex tra p ieces of eq uipment for tem pora ry use an d
how to effect replacemen t of broken items.
6. Pro vide a sheet of paper to be signed by each student in cert ification that all equipmen t listed on page x iii has been received by hi m .
91
7. The instructor may prefer to provide some or all o f the items listed on page X I V
whic h th is ma n ual re qu ire s the st ude nt to provide. T hi s is, of co urse, a matter to be dec ided
locall y. Items not to be fu rn ished b y the stud ent himself sho uld be provided b y th e instr uctor; hence thi s reminder.
Tns
SE C O N D P E R IO D;
l. Check to see th at items to be provided by the studen t an d brought to th e laborator y
have been procured.
2. Give a short exam inat ion on the material in the sections " T o the Studen t" an d
" Safety in the Lab oratory."
3. If desired, provide a few sam ple wash bo ttl es as models. It is helpf ul to ex hi bi t
one or two glarin g examples of poor work.
4. Exam ine the studen t's stirring ro ds, bent tubing, and wash bottl e. \ Vhen properl y
accomplished , ini t ial man ual (in three places) .
5. Exam in e student's en tr ies at the end of the sections on the b urner and on glass
worki ng.
L ATER L AB ORATORY PER IO DS:
Ad d ition al rem ind ers to in it ial the man ual and ex am ine the studen t's work will not
be cited. T he suggestions whic h follow list o nly tho se po ints to be not ed wh ich are not
easil y recogni zed in a cursory reading of the man ual. Also, since some st udents begin to
sho w more ra pid p rogr ess than others at th is po int, fu rt he r reference to items on a n um bered
day basis can not be m ade. I n the order in whic h they ap pear in the manual, t hen ;
l. Demo nstrate how to re ad the barometer.
2. If nece ssary, d emo ns trate collect io n of CO 2 b y d irect (downward) displacement of
th e an- in the collecting bottle.
3. If desire d , set u p a sample filter in g ex hibit. I t is helpful to use several pieces of
filter paper, first fold , second fold, ctc ., in a series to show the successive steps of fold ing,
tea ring the corner, fitting to the fun nel, etc.
4. Set th e la borator y oven at ca. 1100 C for drying the barium chroma te.
5. See that b urets are ava ila ble, as t he students req u ire them .
6. As the studen ts finish Part I collect their wr-it te n assignments o n th e five most
portant safety ru les.
7. Di vide the students in to pairs, as they become ready, for the work in Part I I.
92
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