Effects of anions on magnesium flame emission in flame photometry
by Glen F Anderson
A THESIS Submitted to the Graduate Faculty IN partial fulfillment of the requirements for the degree
of Master of Science in Chemistry at Montana State College
Montana State University
© Copyright by Glen F Anderson (1954)
Abstract:
This investigation was prompted by the conclusive results obtained in studying the anionic influence on
the flame intensities of calcium emission by flame photometry (1). Although little or no resolution was
exhibited by oxy-acetylene flame on magnesium as was found with calcium, the oxygen-hydrogen
flame showed excellent resolution for magnesium. Perchlorate ion enhances the flame emission,
whereas phosphate ions depress the values in the analysis of magnesium. The arsenate, sulphate,
borate, dichromate also exhibit a depressing action. It has also been observed that when any two or
more of the above anions are present in the same solution, some knowledge of the anionic system is
necessary for an accurate determination of magnesium by flame photometry. EFFSCTB QF MTCTWS OW HAGNSSimT
FLAMS HiTSSION IN FLAMS PHOTOMETRY
by-
■
Glen F.. Anderson
A-THESIS '
Subm itted to th e Graduate F a c u lty
IN
p a r t i a l f u l f i l l m e n t o f th e req u irem en ts
f o r th e d eg ree o f
M aster o f S c ie n c e i n C hem istry
at
Montana S ta te C o lle g e
Approved;
Head, Major !Department
Chairman, Examining Committe"e
L ean, Graduate D iv is io n
Bozeman, Montana
Septem ber, 195h
/ 3 ?/
P\ M
^
- 2 TABLE OF CONTENTS
S e c tio n
Page
I
ABSTRACT ............................................................................................................................
3
TI
HISTORY AND DEVELOPMENT.......................................................................................
Ix
III
INTRODUCTION ...................................................................................................................
3
IV
EXPERIMENTAL....................................................................................................................
6
V
DISCUSSION .......................................................................................................................
9
VT
ANALYTICAL SIGNIFICANCE
.......................................................................................
2b
V II
THEORETTCAI IMPLICATIONS.......................................................................................
2$
V III
SUMMARY.................................................................................................................................
31
IX
ACKNOWLEDGMENTS.........................................................................................................
32
X
LITERATURE CITED .........................................................................................................
33
- 3 -
I . ABSTRACT • ■
T h is X nvestirgatro rr wa-s- prompted b y th re cone Ixrsrve' re s u i t s obtained' in
stu d y in g t h e ' a n i o n ic i n f l u e n c e •on th e fla m e i n t e n s i t i e s o f calcip m em issio n
'ty fla m e photom etry ( I ) .
A lthough l i t t l e or no r e s o lu t io n was e x h ib ite d by
o x y -a c e ty le n e fla m e on magnesium a s was found w ith c a lciu m , th e oxygenhydrogen flam e showed 'e x c e lle n t r e s o lu t io n f o r magnesium.
P e r c h lo r a te io n
enhances th e flam e e m is s io n , w hereas phosphate io n s d ep ress th e v a lu e s i n
th e a n a ly s is o f magnesium.
The a r s e n a t e , s u lp h a te , b o r a te , d i chromate
a ls o e x h ib it a d e p r e s s in g a c t io n .
I t has a ls o been ob served t h a t when any
two or more o f th e above a n io n s a re p r e s e n t i n th e same s o lu t io n , some
knowledge o f th e .a n io n ic system -ig n e c e s s a r y f o r an a c c u r a te d eterm in a tio n
o f magnesium by fla m e photom etry.
-Ij1IT . ."HTSTOET AKD' DMSCOTMOTT
The u rg en t need f o r ex trem ely ra p id and a c c u r a te sodium determ ina­
tio n s ' on la r g e numbers o f sam ples le d to th e developm ent o f ^he flam e
p h otom eter.
P r e v io u s ly e x i s t i n g methods employed were r a th e r ^ime con­
suming and r e q u ir e d c o n s id e r a b le sample p r e p a r a tio n p a r t ic u l a r ly .in c a s e s
where o n ly t r a c e s o f "sodium were p r e s e n t .
The groundwork f o r th e developm ent o f flam e photom etry was .s e t down by
Lundegardh i n h is -b o o k ( 9 ) 5 d e s c r ib in g a method o f sp ectro -cfrem ica l a n a ly s is
which, in c lu d e d a l i s t i n g o f l i n e s c h a r a c t e r is t ic o f some 3U elem en ts i n
193k.
■
'
- Although in s tr u m e n ta tio n was d ev elo p ed and com m ercially a v a ila b le in
Germany p r io r to. u se i n t h is c Ountry5 d e s c r ip t io n o f th e e s s e n t i a l s f o r an . .
x
'
'
'
a l y s i s o f l i n e s d e s c r ib in g th e u se o f a ir - a c e t y le n e flam e f i r s t appeared i n
.th is cou n try i n T9I4I4, ( 2 ) .
The f i r s t r e a l l y s u c c e s s f u l a n a l y t i c a l proced u re i n America was de­
velo p ed and p u b lish e d i n 1945 by R.B. Barnes e t a l ( 2 ) , whereby i t was.
r e a d ily dem onstrated th a t any o f th e c h a r a c t e r is t ic r a d ia tio n ^ , i f is o l a t e d
by p a ssa g e through proper f i l t e r s , w i l l , upon s t r ik in g a p h o t o s e n s it i v e ■
elem en t, g iv e r i s e to an e l e c t r i c a l im p u lse which i s a f u n c tio n o f th e quan­
t i t y - o f th e r e s p e c t iv e m e ta l p r e s e n t i n the. sam ple.
I n :the"-oast" te n -y e a r s c o n s id e r a b le a t t e n t io n has been d ir e c t e d t o th e
improvement o f in str u m e n ta tio n and te c h n iq u e , th ereb y -en h a n cin g th e scope
o f t h i s r a p id , a c c u r a te and r e l a t i v e l y sim p le approach to a n a l y s i s .
Tt is
r e a so n a b le to assume th a t th e s u r fa c e has o n ly been touched in t h i s f i e l d .
- 5 ■ I I I . IFTRODUCITON
.
.
.
.
A lthough in s tr u m e n ta tio n consumed m ost o f th e tim e d ev o ted to flam e
photom etry i n t h e .e a r ly y e a r s s in c e Lundegardh• ( 9 ) ,-proposed and e s t a b lis h e d
h i s e a r ly m ethod, c o n s id e r a b le work has been done in t h is f i e l d during th e
p a s t te n y e a r s . • Q u a n tita tiv e a s p e c ts o f b o th c a t io n and a n io n in f lu e n c e
have been in v e s t ig a t e d and shown to a f f e c t th e i n t e n s i t i e s o f many charac­
t e r i s t i c fla m e e m is s io n s .
C o n sia e r a o ie in v e s t ig a t i o n has ]peen done w ith th e
c a t io n ic in f lu e n c e , b u t th e sea rch in t o th e a n io n ic , e f f e c t s h as been
lim it e d ( 3 - 5 - 6 - 7 - 8 - 1 1 ) .
R ecent s t u d ie s ( I ) ,
( 6 ) , ( 8 ) , have e s t a b lis h e d th e
n e c e s s i t y f o r a cco u n tin g f o r a n io n ic e f f e c t s i n a c c u r a te q u a n t it a t iv e work.
T his paper r e p o r ts on some a n io n ic e f f e c t s on magnesium a n a ly s is byflam e p h otom etry. - D ata o b ta in ed by adding in crem en ts o f some te h a c id s to
a stan d ard magnesium c h lo r id e s o lu t io n a r e p r e s e n te d .
—6 —
IT . MPERIMEMrAL
In t h i s i n v e s t i g a t i o n , a Beckman D.IT. sp ectro p h o to m eter Model "9200 w ith
p h o to m u ltip lie r attach m en t was u se d .
Oxy-hydrogen flam e d isp e n se d through
.a number 1*020 hydrogen a to m izer was th e e x c i t a t io n so u r c e , ex ce p t f o r a
sm a ll p o r tio n o f th e experim ent d ev o ted to a com parison o f em issio n s when
an oxy^ace t y le n e ' flam e was u se d .
R e la tiv e r e a d in g s were made w ith stan d ard magnesium c h lo r id e - s o lu t io n s
c o n ta in in g in crem en ts o f v a r io u s a c i d s .
The magnesium c h lo r id e standard
was prepared by d is s o lv in g magnesium rib b on i n h y d r o c h lo r ic acp d , evapora­
t in g to d ry n ess and d ilu t i n g w ith d i s t i l l e d w ater to produce a ; 0.02M mag­
nesium c h lo r id e sto c k s o lu t io n .
T h is in turn was used to prepare th e i n ­
d iv id u a l stan d ard s by proper d ilu t i o n to th e v a r io u s c o n c e n tr a tio n o f th e
a cid s' a s in d ic a t e d .
Magnesium has tw o' l i n e s a t wave le n g t h s o f 2 8 9 .2 mu.and 371 mu.
wave le n g th s a re f o r magnesium o x id e, bands.
These
R e so lu tio n " a t e i t h e r w ave­
le n g th was good w ith p o s s ib ly a l e s s e r background in t e r f e r e n c e a t th e 371
mu. s e t t i n g , and th e l a t t e r was a r b i t r a r i l y chosen f o r - t h is - e x p e r im e n t .
O ther in stru m en t c o n d itio n s in c lu d e d a s l i t w idth o f - 0 . 0 7 'ipn w ith a .
rea d in g o f 100 on th e ■tr a n sm itta n cy s c a le f o r a standard O.OOi* M mag- ■ nesium c h lo r id e s o lu t io n .
T his rea d in g was o b ta in ed by ad ju stm en t o f th e
m o n o c h r o m a tic -w e u sr tiv ity ' c o n t r o l.
gen and 12 P.S.I". f o r oxygen .
Gas p r e s s u r e s w ere I* P.5.1", f o r h yd ro- .
Optimum c o n d itio n s were e s t a b l i shed fo r each
-sep a ra te''operation-w orth th e n e e d le v a lv e i n th e hydrogen- l i n e p rpVided on
th e in s tr u m e n t.
D urin g th e co u rse o f sample runs c o n s ta n t r e fe r e n c e to th e
e s t a b lis h e d stan d ard c o n d itio n s was made.
T h e.n e cessa r y m inor ad ju stm en ts
~ 7 were f a c i l i t a t e d by th e s e n s i t i v i t y c o n t r o l;
zeroed by th e dark- c u rre n t - c o n t r o l.
lfe e d le d r i f t was c o n s ta n tly
For th e wave l e n g t h 371 mu,, th e b lu e
s e n s i t i v e p h o to m u ltip lie r ' tube was u sed .
In stru m en t warmup procedure i n ­
clu d ed a. te n m inute p e r io d w ith th e s e l e c t o r s w itc h a t llCHlCETlf..
Another
te n m in u tes were a llo w e d , a f t e r sw itc h in g to 11. I fl and •th e b a tte r y -b o x • ■ s e n s i t i v i t y tu rn ed to " F u ll11.
"The oxygen and hydrogen p r e s s u r e s were low •
a t l i g h t i n g and then b rought to o p e r a tin g p r e s s u r e s , w ith d i s t i l l e d w ater
b e in g a s p ir a te d t o a v o id e x c e s s iv e t i p h e a t to th e a to m ize r.
The h ig h ly s e n s i t i v e in stru m en t co n d itio n s* w h en .o x y -h y d rp g en flam e was
u sed f o r magnesium e x c i t a t i o n made r e p r o d u c ib le r e s u l t s im p o s s ib le when
even th e s l i g h t e s t l i g h t le a k s e x i s t e d .
T R ep rod u cib ility was u ltim a te ly -
accom p lish ed by co v er in g th e " p u ll arm" opening- f o r th e - f ilt e r - s l i d e w ith
a s t r i p o f b la c k masking ta p e .
T h is m inute so u rce o f l i g h t d id n o t cause
s e r io u s n e e d le f lu c t u a t io n w ith o x y -a c e t y le n e fla m e .
- ■-
W ith ■in stru m en t c o n d itio n s e s t a b lis h e d f o r a rea d in g o f 100 on th e
tra n sm itta'ncy s c a le a s d e s c r ib e d , s l i t w idth ad ju stm en t was m&de to 0 .0 6 3
mm to g iv e a rea d in g o f '8 0 .
A ll a n io n ic e f f e c t s were stu d ip d a t th e 100
rea d in g or 80 rea d in g a s c o n d itio n s w arran ted .
m itte d an in c r e a s e o r ,d e c r e a s e to be n o te d .
The s e t t i n g a t '80 p er­
—8 —
.002
003
004
.0 0 5
MOLAR CONCENTRATION OF MgCl1
F ig u r e I .
R e la t iv e B n is s io n I n t e n s i t i e s o f
Pure Magnesium C h lo rid e S o lu t io n s .
Q 60
.002
.0 0 4
ooe
.
00#
MOLAR CONCENTRATION OF ACIO
F igu re 2
Cursory Exam ination o f V arious A cid C o n cen tra tio n s
on I n t e n s i t y o f Magnesium Oxide E m ission .
- 9 ■ V. DISCUSSION
-
F igu re #1 shows th e r e s o lu t io n o f magnesium c h lo r id e s o lu t io n w ith ox y -
hydrogen flam e em issio n a n t h e f e a s i b i l i t y o f magnesium a n a ly s is a t low
" co n cen tra ti one -w ith fla m e p h otom etry.
A cu rso ry exam in ation o f th e a d d itio n o f v a r io u s a c id s t p -magnesium
c h lo r id e s o lu t io n i s shown i n F igu re # 2 .
The r e l a t i v e in s i g n i f i c a n c e o f
e f f e c t s on magnesium c h lo r id e by e it h e r h y d r o c h lo r ic acid- or n i t r i c a c id
in d ip a t e s th e im p r o b a b ility o f hydrogen io n in f lu e n c e on th e magnesium
flam e e m is s io n „
-
The d e p r e s s in g e f f e c t n o ted f o r p h o sp h a te, a r s e n a te , s u lf a t p and b or­
a t e io n s a re h ig h ly s i g n i f i c a n t .
For in s t a n c e , as i n th e c a se o f phosphate
io n , a magnesium to phosphate r a t io o f 2 :1 red u ces th e r e l a t i v e rea d in g f o r
I
magnesium n e a r ly £ 0 $ .
P e r c h lo r a te io n i s unique i n i t s a c t io n and enhances
th e rea d in g s u f f i c i e n t l y to warrant a more d e t a ile d exam in ation a s do the'
d e p r e s s a n ts .
F ig u r e # 3 "shows- th e " r e s u lts o f d ata taken when v a rio u s l e v p l s o f mag­
nesium c h lo r id e were used and in c r e a s in g amounts o f s u lf u r ic a c id added.
In stru m en t c o n d itio n s 'w e r e e s t a b lis h e d a t th e rea d in g shown fp r th e O.OOlt M
magnesium c h lo r id e l e v e l and zero a c id c o n c e n tr a tio n and m ain ta in ed when
d a ta were tak en a t th e rem ainin g l e v e l s . , , The r e s u l t s in d ic a t e tjia t a
m o lecu la r r a t i o may be i n e f f e c t .
A maximum e f f e c t seems to be e s t a b lis h e d
i n a l l c a s e s b y th e tim e t h e r a t io o f magnesium to s u lf a t e o f "1 :2 has been
rea c h e d , n o ted by th e d o tte d l i n e .
> . A rsen ic a c id in crem en ts when added to v a rio u s c o n sta n t c o n c e n tr a tio n s
o f magnesium c h lo r id e a s shown i n F ig u r e
d e f i n i t e l y " e s t a b l i s h a c o n sta n t
- 10 -
MOLAR CONCENTRATION'OF AGIO
F ig u re 3•
E f f e c t o f V arying S u lf u r ic A cid C o n cen tra tio n s
a t D if f e r e n t Magnesium C h lo rid e L e v e ls on
I n t e n s i t y o f Magnesium Flame E m ission .
■004
_
M
PO* M
■001
M
■0004N
002
.004
00 #
.000
MOLAR CONCENTRATION O F ACID
F ig u r e U.
E f f e c t o f V arying A rsen ic A cid C o n cen tra tio n s
a t D if f e r e n t Magnesium C h lo rid e L e v e ls on
I n t e n s i t y o f Magnesium Flame E m issio n .
Jm m
-
1 1
-
OOI M
.OOZ
.0 0 4
00#
MOLAR CONCENTRATION OF ACID
F ig u re 5 .
E f f e c t o f Varying Phosphoric A cid C o n cen tra tio n s
a t D if f e r e n t Magnesium C h lo rid e L e v e ls on
I n t e n s i t y o f Magnesium Flame E m ission .
LEVELS
.0 0 2
.0 0 4
.0 0 6
.
MgCIl
002
M
0004
M
00#
MOLAR CONCENTRATION OF ACID
F igu re 6 .
E f f e c t o f V arying P e r c h lo r ic Acid C o n cen tra tio n s
a t D if f e r e n t Magnesium C h lo rid e L ev els on
I n t e n s i t y o f Magnesium Flame B n is s ion.
- 12 v a lu e but o n ly a f t e r a v ery s l i g h t in c r e a s e i n rea d in g s i n eaph c a se j u s t
a f t e r a minimum v a lu e has been a t t a in e d .
This minimum v a lu e appears to
occu r a t ' a-'-magnesium- ter araenatenratiro o f I s l .
~TrrsLi-umeni-c o n d itio n s were
e s t a b lis h e d for" OlOOii M magnesium c h lo r id e to read TOO a t a s l i t w idth o f
0 . 0? mm f o r a l l curves'.
F ig u r e #5' I lT u s tr a te s ; a " d etailed exam in ation o f th e e f f e c t s , o f th e
p h osp h oric a c id , th e m ost d e p r e ssa n t o f th e a c id s used i n i t s a c t io n .
As
in d ic a t e d p r e v io u s ly w ith b o th s u lf u r ic and a r s e n ic a c i d s , p h osp h oric a c id
seems to p r e s e n t a m o lecu la r r a t io a t th e minimum r e a d in g .
"The magnesium
to phosphate r a t i o o f T s l i s n o ted b y th e d o tte d l i n e i n th e graph.
Stan­
dard O.OOI4 magnesium c h lo r id e was read w ith th e in stru m en t rea d in g s' a t IOO
on th e tr a n sm itta n c y s c a le a t 0 .0 7 mm " s lit w id th .
F ig u r e #6 v e r i f i e s "the dou ble r i s e shown i n th e c u r so r y exam ination f o r
th e p e r c h lo r ic a c id c u r v e .
I n a l l c a s e s a r i s e i s n oted e a r ly f o r p er­
c h lo r a te io n w ith a l e v e l i n g o f f , fo llo w e d by a second r i s e t o a near max­
imum.
A m o lec u la r r a t i o does n o t appear a s d e f i n i t e w ith th e F p r c h lo r ic
a c id -curve a s was- in d ic a t e d "with th e d e p r e s s a n ts , a lth ou gh 'b eyon d th e mag­
nesium to p e r c h lo r a te r a t io d fT s'2 th e enhancement i s f o r a l l p r a c t ic a l
p u rp oses n e g l i g i b l e .
The q u e s tio n now a r i s e s a s to th e e f f e c t on magnesium c h lo r id e flam e
em ission .w h en th e v a r io u s a c id s are to g e th e r i n th e s o lu t io n .
To determ ine
w hether two d e p r e ssa n ts in s o lu t io n w ith magnesium would fu r th e r d ep ress th e
re a d in g s by a d d it iv e e f f e c t , or w hether two d e p r e ssa n ts would com pete, a
s e r i e s o f runs in c o r p o r a tin g com b in ation s were made.
--
F ig u r e '# 7 j shows th e e f f e c t on magnesium fla m e em issib h by adding
-1 3
-
O
□
.0 0 4 M
.0 0 4 M
MfCIt V INCWMCNTt Nt M 4
MgCIt VWCNCMCNTt N1M l4
A
004 M
MeCI1 V A O t I ^ M 4 V W CNCtENTt M4NO4
X
004 M
MfCIt V O Ot H1 NO4 V NKNCMCNTt I ^ t q 4
MOLAR CONCENTRATION OF AGIO
F ig u r e 7•
E f f e c t o f S u lfu r ic -P h o s p h o r ic Acid M ixture
on I n t e n s i t y o f Magnesium Flame E m ission .
.0 0 4
O
□
.0 0 4 M MgCIt VINCRCMCNTt N4Neq4
.0 0 4 M MtCIt VWCNCMCNTtNt Pq4
A
.0 0 4 M M gcit V A oiM M t NW^VINCMCNCMTt H4 P q ,
.OOC
MOLAR CONCENTRATION OF AGIO
F ig u r e 8
E f f e c t o f A rsen ic-P h o sp h o ric Acid M ixture
on I n t e n s i t y o f Magnesium Flame E m ission .
- I h -
00«
H
HfClt * MCRIMCNTt Mt BOl
□
.0 0 4
A
.0 0 4 M M fC ^ * O O t M M jB O ,* MWMtMMMTS M /f l
.0 0 4
M MfCIt * MCMtMCMTB Mt Mflt
M M fC I,* .O O S MHt M ^ *
.0 0 4
. 004
MOLAR CONCENTRATION OF ACIO
F igu re 9 .
E f f e c t o f B o ric-P h o sp h o ric A cid M ixture
on I n t e n s i t y o f Magnesium Flame E m issio n .
O
.0 0 4 M
MfCI8 + INCREMENTS Hf SO4
O
.0 0 4 M
MfCI8 +INCREMENTS H3 AtO4
A
.0 0 4 M
MfCIf + INCREMENTS H3 PO4
X
.0 0 4 M
MflCI8 + .0 0 4 M HjSO4 *
.0 0 4
O O tM H3A efl,* WCMtMtNTf H3 Pfl4
.0 0 «
MOLAR CONCENTRATION OF ACID
F ig u re 10
E f f e c t o f S u lfu r ic -A r s e n ic -P h o s p h o r ic Acid
M ixture on I n t e n s i t y o f Magnesium Flame E m ission
in crem en ts o f phosphate io n to a c o n s ta n t m ix tu re o f magnesium c h lo r id e and
s u lf u r ic a c id i n one c a s e , and adding in crem en ts o f s u lf a t e io n to a con­
s t a n t m ixtu re o f - magnesium c h lo r id e and ph osp h ate io n i n th e second s it u a ­
t io n .
The r e s u l t s "show t h a t th e d e p r e s s in g e f f e c t o f s u l f a t e 3.on does n o t
add to th e d e p r e ssin g e f f e c t o f ph osp h ate io n , but r a th e r th e e f f e c t i s a
com peting one- determ ined u lt im a t e ly by th e io n e x i s t i n g i n ex p ess in th e
s o lu t io n .
F u rth er i t shows t h a t th e rea d in g s approach th e same ipinimum
v a lu e f o r th e io n " in e x c e s s , a s was o b ta in ed when th a t io n was "the s o le de­
p r e s s a n t.
F igu re # 8 , w herein p h osp h oric a c id and a r s e n ic a c id a r e uped i n combin­
a t io n with, a s o lu t io n o f magnesium c h lo r id e , fo llo w s e s s e n t i a l l y th e same
p a tte r n a s shown i n F igu re # 7 •
I t sh ou ld be n o ted however, ^ hat a s the i n ­
crem ents o f •a r s e n a te io n a re added to th e c o n s ta n t m ix tu re o f magnesium
c h lo r id e and phosphate io n , th e d e p r e ssa n t e f f e c t o f phosphate was ex er ted
f o r a c o n s id e r a b le tim e and n o t u n t i l th e a r s e n a te io n was in c r e a s e d to
n e a r ly th r e e f o l d t h a t o f p h o sp h a te, d id th e curve approach th e minimum fo r '
a r s e n a te .
F ig u re #9 i l l u s t r a t e s th e e f f e c t o f th e s tr o n g ly d e p r e ssa n t phosphate
'±orr im 'combi"na"tion--with' a-m i I d ly -d ep ressan t b o r a te io n . ' I n tfie c a se o f
th e in c r e a s in g amounts o f b o r a te , added in crem en ts o f b o r a te n ev er ov er­
come th e o r i g in a l d e p r e ssin g a c t io n o f th e phosphate io n even a t the b o r - •
a t e to phosphate r a t i o o f 3 s l i n fa v o r o f' th e b o r a te io n .
F ig u re ^lD i l l u s t r a t e s th e answer to th e q u e s tio n as to th e e f f e c t s
o f a com b in ation o f th r e e d e p r e ssa n ts i n s o lu t io n w ith magnesium c h lo r id e .
As' e x p e c te d , th e e f f e c t s a r e s t i l l c o m p e titiv e w ith th e ph osp h ate minimum
—l 6 —
O
.0 0 4 M Mgci1 + INCWMtNTS H1SO4
D
0 0 4 M Mgci1 4- MCNtMCNTS HgAeO4
6
.0 0 4 M MgCI1 * . 0 0 3 M HgAsq, ♦ INCWNENTS H1 SCl4
X
.0 0 4 M MyClg 4 . 0 0 S M Mt SO4 T INCNtMtMTSH1MO4
.0 0 4
OOS
MOLAR CONCENTRATION OF ACIO
F ig u r e 11«
E f f e c t o f S u lf u r ic -A r s e n ic A cid M ixture
on I n t e n s i t y o f Magnesium Flame E m ission
O
O
A
.002
.0 0 4
.0 0 4
.0 0 4
M MgCI1 + INCREMENTS HCMI4
M MgCI1 T INCREMENTS H4RO4
M MgCI1 * OOSHCIO4 T INCREMENTS M1 RO4
.0 0 4
006
OOS
MOLAR CONCENTRATION OF ACID
F ig u re 12
E f f e c t o f P e r c h lo r ic -P h o sp h o r ic Acid M ixtu re
on I n t e n s i t y o f Magnesium Flame E m issio n .
- 17 -
O
.0 0 4 M Ht Clt + w e n t W W iS MCH^
D
.0 0 4 M Mt CIl + MCtttMOiTS H ,*4%
A
.0 0 4 M Mt CIt + OOSM MCK^+
MOLAR CONCENTRATION'OF AGIO
F ig u r e 1 3 .
E f f e c t o f P e r c h lo r ic -A r s e n ic A cid M ixture
on I n t e n s i t y o f Magnesium Flame E m issio n .
20 -
.0 0 4 M MQCIt + IMCMCMCNTt MCK^
.0 0 4 M MgCI8 + MCNCMCNTt H8SQt
0 0 4 M MQCI8 + OOS M MCIC^+ WCNCMCNTt MgtQjt
004
.OOS
MOLAR CONCENTRATION OF ACID
F ig u re l l u
E f f e c t o f P e r c h lo r ic - S u lf u r ic A cid M ixture on I n t e n s i t y
o f Magnesium E m ission i n Oxygen-Hydrogen Flame.
— 18 —
b e in g .a tta in e d as th e in crem en ts o f p h osp h oric acid" a re addgd. T t i s i n t e r ­
e s t in g to n o te th a t th e s u l f a t e and a r s e n a te io n s p r e s e n t a p a r t i a l l y
a d d it iv e a c t io n a s i l l u s t r a t e d by th e i n i t i a l rea d ip g f o r th e m u lt ip le com­
b in a tio n cu rve marked by th e "x" p o in t s .
F ig u re # 1 1 , showing th e e f f e c t s o f s u lf u r ic acid' and. a r s e n ic a c id pro­
v id e s n o ■new e v id e n c e b u t r e a ffir m s th a t h e r e to fo r e b rought f o r t h .
The
c l o s e p r o x im ity o f th e l e v e l s exten d ed beyond th e minimum p o in t makes th e
r e s u l t s more d i f f i c u l t to i l l u s t r a t e , however th e approach to th e e x c e ss
a c id l i n e i s n o t ic e a b l e .
The e f f e c t s ' o f th e d e p r e ssa n t a c id s i n com bination p it h th e enhancing
p e r c h lo r ic a c id ' a re "shown i n F igu re # 1 2 , F ig u re #13 and F ig u r e #iLt.
F igu re #12 e s t a b lis h e s a .p u rely c o m p e titiv e n atu re o f t h e a p id s .
-Per­
c h lo r ic a c id m a in ta in s a h ig h e r rea d in g for- th e same c o n c e n tr a tio n o f phos­
p h o ric a c id than e x i s t s i n th e absence, o f th e p e r c h lo r ic a c id , however, as
b e f o r e , th e p h osp h o ric a c id minimum v a lu e i s rea ch ed .
The a tta in m en t o f
t h i s minimum however i s a t a p h osp h oric a c id c o n c e n tr a tio n a lm o st double
th a t r e q u ir e d to reach the' minimum w ith o u t th e p e r c h lo r ic a c id .
F ig u re #13 f o llo w s th e p a tte r n a s e s t a b lis h e d above i n F igu re # 1 2 .
However, th e d e p r e ssa n t n atu re o f th e a r se n a te io n i s n o t s u f f i c i e n t to
1overcome c o m p le t e ly •th e enhancing a c t io n o f th e p e r c h lo r ic a c id w ith in th e .
c o n c e n tr a tio n Tim irts i l l u s t r a t e d .
■Figure # l l |, whereby p e r c h lo r ic a c ifi and s u lf u r ic a c id arp u sed in com­
b in a tio n w ith magnesium c h lo r id e adds n o th in g new.
I n th e cu rso ry exam in ation o f th e a c i d s . F igure # 2 , chrom ic a c id r e ­
a c te d in a manner t h a t was perhaps u n ex p ected .
A lthough no fu r th e r
19 -
.0 0 4 H MfCIl ♦ MCMCMINTt HCM),
.0 0 4 M MfCit ♦ M C X M iirrt e r e .
.0 0 4 M MfCIt 4- JO M M HCKfc ♦
.0 0 4
.O O t
MOLAR CONCENTRATION OF AGIO
F igu re l £ .
E f f e c t o f P erch loric-C h rom ic A cid M ixture
on I n t e n s i t y o f Magnesium Flame E m issio n .
-------------- -----------------------------------
O 60 1
£
50 ‘
UJ
I*
UJ
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0 0 4 M Mq CI1 -MNCRCMENTS NClO4
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.0 0 4 M MgCIg+MCREMENTS H1 SC^
A
.0 0 4 M MQCIa 4 -.0 0 8 M N C K ^-f INCREMENTS HgSQ1
__ I________ I
004
I
OOt
MOLAR CONCENTRATION OF ACID
F ig u re 1 6 .
I_________I_________I
00#
.010
E f f e c t o f P e r c h lo r ic - S u lf u r ic Acid M ixture on I n t e n s i t y
o f Magnesium E m ission i n O xygen-A cetylen e Flam e.
— 20 —
.001 M C eC l,* WCMMIfTS HCtO4
.001 M CeCfc+WCNCMCIITt 1V O 4
.001 M CeCIt + .OOt M M CKt+ WC
.0 0 4
OOS
MOLAR CONCENTRATION OF AGIO
F ig u re 1 7 .
.oos
E f f e c t o f P e r c h lo r ic - S u lf u r ic Acid
M ixture on I n t e n s i t y o f Calcium
E m ission i n O xygen-A cetylen e Flam e.
to -
O .001 M CeClt + NMlRCMClfTS NOM t
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WCMCMCMTS
A
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. 0 0 1 M M OM t+
.0 0 4
M gS^
00#
MOLAR CONCENTRATION OF AC*)
F ig u re 1 8 .
E f f e c t o f P e r c h lo r ic - S u lf u r ic Acid
M ixture on I n t e n s i t y o f Calcium
E m ission i n Oxygen-Hydrogen Flam e.
21
O
OOl M C tC Ig ♦ M CtEHENTt HCN^
O .001 M C t e it + INCRCMCNTt HgEQ,
A .001 M
CtCIg +
OOt M HCKt+ MCRCMCNTt N ,R < t
.00«
.OOt
MOLAR CONCENTRATION OF ACIO
F ig u r e 19 .
E f f e c t o f P e r c h lo r ic -P h o s p h o r ic A cid M ixture on
I n t e n s i t y o f Calcium E m ission i n Oxygen-Hydrogen Flame.
- 22 exam in ation was made a t t h i s tim e, th e d e p r e ssin g a c t io n to a minimum and
th en a r i s e i n th e curve sh ou ld be f u r t h e r in v e s t ig a t e d i n l i g h t o f th e pyro
io n p o s tu la t e made by Baker & Johnson ( I ) *
F ig u re
' i l l u s t r a t e s th e r e ­
s u l t s when chrom ic a c id was u sed i n com b in ation wi^b. p e r c h lo r ic a c id w itfi a
p u r e ly c o m p e titiv e a c t io n f o r th e a v a il a b l e io n s b ein g shown.
To attem p t t o shed more l i g h t in t o th e n a tu re o f th e r e s u l t s d e sc r ib e d
thus f a r , an- o x y -a c e ty le n e flam e was used to e x c i t e th e m ix tu res o f s u l­
f u r i c a c id - p e r c h lo r ic a c id i n com b in ation w ith magnesium c h lo r id e .
(T hese
s o lu t io n s e x c it e d w ith oxy-hydrogen flam e were i l l u s t r a t e d i n T lgu re # l b . )
These r e s u l t s a s shown i n F ig u r e #16 f o ll o w th e fe a t u r e s o f th e hydrogen
flam e e x a c t ly , d i f f e r i n g o n ly i n th e e x t e n t o f d e p r e ssin g or enhancing
v a lu e s - o f t h e in d iv id u a l apids" on th e stand ard magnesium f Iamip e m issio n .
Tn l i g h t o f th e work p r e v io u s ly done w ith th e calciu m em issio n when
e x c it e d w ith o x y -a c e ty le n e fla m e , s o lu t io n s o f calciu m c h lo r id p w ith m ix­
tu r e s o f p e r c h l o r ic - s u lf u r ic a c id s were s u b je c te d to o x y -a c e ty le n e fla m e .
The anomalous r e s u l t s o b ta in e d ))y'"Baker & Johnson "(1)» were r e a ffir m e d a s
shown i n F ig u r e # 1 7 .
However th e s e s o lu t io n s s u b je c te d to th e oxy-hydrogen fla m e . F igu re
# 1 8 , showed no anom oly, b u t a s i n o th er c a s e s d is c u s s e d , p o r tr a y s th e
p u r e ly c o m p e titiv e n a tu re o f th e io n s .
I p a d d itio n , th e in c r e a s e d e x te n t
o f “d e p r e s s in g a c t io n o f th e s u l f a t e io n i n th e oxy-hydrogen f lapie i s a g a in
-a p p a ren t.
"The- p erch fo ra t e ■"ion however i s n o t ic e a b ly low er i n i t s enhance­
m e n t-v a lu e s , -±n- th e oxy-hydrogen ■fla m e and a t t a in s i t s maximum v alu e a t
r e l a t i v e l y s m a ll c o n c e n t r a t io n s .
-
The anomoly shown, s im ila r to F ig u r e # 1 7 , w ith p e r c h lo r ic -rphosphoric
- 23 a c id m ix tu res on ca lciu m c h lo r id e by "Baker & Johnson ( I ) , i s n o t observed
"when th e s o lu t io n s a re s u b je c te d to qxy-hydrogen fla m e . F ig u re # 1 9 .
•
—
2U
—
■V I. ANALYTTCAL SIGNIFICANCE
The e v id e n c e e s t a b lis h e s t h a t a working curve f o r th e d eterm in a tio n o f
magnesium by flam e photom etry w ith oxy-hydro'gen fla m e i s f e a s i b l e .
However
a t th e lo w c o n c e n tr a tio n s o f magnesium t h a t can be determ ined i n t h is
manner, i t i s o f paramount im p ortan ce th a t th e g en era l co m p o sitio n o f th e
s o lu t io n b e in g e x c it e d be n o te d .
A f i l e o f working cu rv es ta k in g in t o
v a c c o u n t th e d e p r e ssa n t e f f e c t o f each o f th e s e v e r a l a n io n s may be p re­
p ared , and th en s e le c t e d f o r th e a n io n whose c o n c e n tr a tio n i s predom inant.
To f a c i l i t a t e th e problem how ever, sh ould th e a n io n s p r e s e n t n o t exceed
th e magnesium to " a n io n r a t i o o f 1 : 1 , a d d itio n o f phosphate io n beyond th e ■
magnesium to phosphate r a t i o o f 1 : 1 w i l l p erm it th e phosphate curve to be
u sed fo r a l l s i t u a t i o n s .
— 2^ V II. IHHDREHCAL •IMPLICATIOHS'
A -summary o f th e d ata p r e se n te d p o se s many p r o b lem s-th a t are worthy o f
n o te and in q u ir y .
-IfVhyy fo r in s t a n c e , i s a g r e a te r d e p r e ssin g a c tio n by some
a n ion s ca u sed on e it h e r magnesium or calcium em issio n when-oxy7-hydrogen
flam e i s u sed than when a n -o x y -a c e ty le n e fla m e i s used?
A ls o , why i s th e
r e v e r s e tr u e i n th e two fla m e s when e x c i t in g ca lciu m a s n o ted i n th e
F ig u r es #1? and #18 w ith p e r c h lo r ic a c id , i n th a t a l e s s e r in p r e a s e i s
shown fo r th e oxy-hydrogen flam e a s compared to th e o x y -a ce^ y len e flam e?
Why i s th e r e an ap p arent l e v e l i n g e f f e c t i n th e p e r c h lo r ic a c id cu rve,
F ig u re # 6 , fo llo w e d b y a secon d r i s e to a n ear maximum?
Why does th e
chromic a c id cu rv e. F ig u re # 2 , d ep ress to a minimum v a lu e apd then r i s e
as shown, w ith in th e c o n c e n tr a tio n s l i m i t s used? - The same b eh a v io r is po t e d b u t -more lim it e d i n t h e - c a s e o f a r s e n ic y a c td , f ig u r e # 2 .
A lso a t
v e r y h ig h c o n c e n tr a tio n s beyond th e l i m i t s employed i n t h i s work, m ost a l l
o f th e a c id s show t h i s ten d en cy to r e t u r n .
Two o th e r p o in t s o f i n t e r e s t may be n o te d . - Why d id th e i n i t i a l rea d in g
o f th e curve through th e "x" p o in ts i n F ig u re #10 o r ig in a t e a t th e i n d i ­
c a te d l e v e l ?
And s e c o n d ly , why was i t im p o s s ib le to d u p lica te- rea d in g s a t
th e s t a r t o f th e exp erim en t w ith oxy-hydrogen fla m e u n t i l l i g h t le a k s were
red u ced -beyond t h a t p o in t tjia t p erm itted o p e r a tio n w ith o x y -a c e ty le r ie -fla m e
a t i d e n t i c a l - In stru m en t-rS e n S it i-U itie s ?
The l a s t two -p o in ts may be e x p la in e d more r e a d ily than th e problem s
.p osed e a r l i e r .
W ith 'reg a rd to' th e l i g h t le a k s , th e problem appears to be
one -of" s ig n a l t o background r a t i o .
I n t h e o x y -a c e ty le n e fla m e t h i s r a t io
o b v io u s ly was h ig h e r than f o r th e oxy-hydrogen flam e i n th e e x c i t a t io n o f
- - -26 magnesium.
Thusjl- an e q u iv a le n t amount o f sp u rio u s l i g h t was n o t - s u f f i c i e n t
to change th e g iv e n r a t i o to th e p o in t o f in t e r f e r e n c e - i n th e p x y -a c e ty le n e
f l a m e . - The in c r e a s e i n background w ith th e sm a lle r r a t io a t t a in e d by th e
oxy-hydrogen flam e was s u f f i c i e n t however to r e q u ir e e lim in a t io n o f a t
l e a s t some o f th e ex tra n eo u s l i g h t .
The i n i t i a l r ea d in g n o ted i n F ig u re #10 a t t a in e d a v a lu e t h a t was n o t
e x c l u s i v e ly c o n t r o lle d by e it h e r th e a r s e n a te io n or s u l f a t e io n , b u t seems
.to be due to a p a r t i a l l y a d d it iv e e f f e c t r e s u lt i n g when th erp i s s u f f i c i e n t
magnesium p r e s e n t to u t i l i z e a l l o f th e a v a ila b le s u l f a t e and a r se n a te
a n io n s .
i n g e n e r a l, th e c o n s is t e n t c o m p e titiv e b eh a v io r o f any twp a n ion s in
com b in ation w ith th e magnesium appears to r e s t w ith th e co n c e n tr a tio n s' o f
th e a n ion s a n d - r e l a t i v e - s t a b i l i t i e s o f th e compounds form ed.
■• - The v a r ia t io n s in th e flam e em issio n i n t e n s i t i e s may p o s s ib ly be b e s t
e x p la in e d by th r e e ap p ro a ch es.
F i r s t , th e fo rm a tio n o f a s t a b le interm ed­
i a t e compound, (a s th e pyro compound proposed by Baker & Johnqon ( I ) and
th e tr ic a lc iu m phosphate compound su g g e ste d by Leyton ( 8 ) ) , w i l l e x p la in
th e r e d u c tio n in i n t e n s i t y v a lu e s i n t h a t th e r e -would b e a l p s s e r number o f
magnesium o x id e m o le c u le s a v a ila b le fo r- e x c i t a t i o n .
I n a d d it io n , t h is
p o s t u la t e i s i n agreem ent w ith th e f a c t t h a t m o lecu la r r a t i o s appear to
e x i s t betw een th e magnesium and d e p r e ssa n t a c id employed a t t h e i n f l e c t i o n
p o in t .
However, t h i s -p r o p o sa l d oes n o t seem to e x p la in .the in c r e a s e in i n ­
t e n s i t y observed" when p e r c h lo r ic a c id i s i n s o lu t io n w ith'the magnesium
c h lo r id e .
-
S e co n d ly , it .m a y be proposed t h a t .t h e v a r ia tio n s in i n t e n s i t i e s a re
-ZTdue to an in c r e a s e or d e c r e a se i n a v a ila b le e n e r g y ■due to th e d ecom p osition
.o f a c i d s . or a n io n s i n th e fla m e .
I f t h i s d eco m p o sitio n adds to th e a v a i l ­
a b le energy,m ore magnesium o x id e co u ld b e e x c it e d , r e s u lt i n g i n an enhance­
ment -as n o ted i n th e c a se o f p e r c h lo r ic a c id .
Conversely^ a d ep ressa n t
■ •
e f f e c t would be ob served i f th e d eco m p o sitio n o f th e a c id or a p io n -absorbed
en ergy.
However, sh o u ld t h i s r e le a s e or a b so r p tio n o f en ergy "by th e a c id
or an io n b e th e s o le o p era n t, th e r e sh o u ld be no ten d en cy to a t t a in the
s to ic h io m e tr ic r e la t io n s h ip s t h a t have been su g g este d a t th e i n f l e c t i o n
p o in t .
Other i n v e s t ig a t o r s ( I ) ,
( 8 ) , ]iave n o ted r a t i o s i n flam e photom etry
work w ith calciu m e m issio n .
A th ir d approach I n e x p la in in g v a r ia t io n s i n i n t e n s i t y ma^r be th a t
some o f th e e x c e s s a c id form s g a se s t h a t p e r s i s t i n th e e x t e r io r p o r tio n s
o f th e fla m e .
These g a s e s cou ld absorb or em it l i g h t o f wave lp n g th
e s s e n t i a l l y th e same a s th e r a d ia t io n b e in g s t u d ie d .
T his e f f e c t would be
r e f l e c t e d a s a d e c r e a se or in c r e a s e i n th e i n t e n s i t y c o n c e n tr a tio n r e ­
la t i o n s h i p .
However, s in c e th e v a r ia t io n s i n i n t e n s i t y a re o b ta in ed from
s im ila r s o lu t io n s f o r e i t h e r wave le n g t h , t h i s phenomenon, i f p r e s e n t, i s
o f more im portance i n th e s ig n a l t o background p roblem s. - I t shpuld be n oted
h e r e th a t L upie & Sherman (TO), have determ ined by experim ent- ah:^ 'c a lc u la ­
t io n - t h a t th e r e e x i s t s a tem perature' d if f e r e n c e o f a b o u t ^OO0 vK i n fa v o r o f
o x y -a c e ty le .n e flam e when compared to oxy-hydrogen fla m e.
TFe cap assume
then t h a t th e d ata o b ta in ed and p r e s e n t e d .in t h i s work were d e r iv e d from a
lower temperature Hvhen 'oxy-hydrogen flam e was in use than when the oxyv
■■ ■■
a c e ty le n e fla m e was em ployed. As p r e v io u s ly m en tion ed , th e s ig n a l to back­
ground r a t i o was sm a lle r when th e o x y -a c e t y le n e flam e was u sed a s compared
- 28 to oxy-hydrogen fla m e .
T his f a c t o r determ ined th e u ltim a te c h o ic e o f ox y -
hydrogen flam e f o r magnesium d e te r m in a tio n s , i n s p i t e o f th e f a p t th a t one
would e x p e c t more e x c i t a t io n o f magnesium to occu r i n th e h ig h p f
tu re o f th e o x y -a c e ty le n e fla m e .
tempera­
The p o s s i b i l i t y o f th e e x is t e n c e o f th e
gaseou s en v e lo p e s i n th e fla m e , th e n a tu re o f which i s dependent on th e
flam e so u r c e , sh ou ld t h e r e fo r e n ot be o v erlo o k ed .
E x p lo rin g th e s e th r e e su g g e ste d b eh a v io rs f u r t h e r , an' attem p t to ex­
p la in th e d if f e r e n c e i n th e amount o f d e p r e ssa n t e f f e c t n o ted in th e two
fla m e s , may be made by r e tu r n in g to th e fo rm a tio n o f th e s t a b le in term ed­
i a t e compound.
Energy would be consumed i n form ing th a t in te r m e d ia te , con­
s e q u e n tly w ith e it h e r fla m e , th e a v a ila b le en erg y f o r e x c i t a t io n would be
red u ced .
T h is would o f co u rse produce a low er i n t e n s i t y v a lu e .
Removing
th e energy n e c e s s a r y f o r th e fo rm a tio n o f t h i s in te r m e d ia te from th e o r i g - .
i n a l en ergy o f e it h e r fla m e , would p erm it th e o r i g i n a l l y h ig h er tem perature
o f th e o x y -a c e ty le n e flam e ( 1 0 ) , to' e x c i t e more magnesium.
Higher* i n t e n s i t y
v a lu e s would be m ain ta in ed when a d ep ressa n t a c id i s p r e s e n t i n th e mag­
nesium c h lo r id e s o lu t io n .
An a lt e r n a t e and e s s e n t i a l l y s im ila r e x p la n a tio n
cou ld be b ased upon th e p o s tu la t e th a t th e in te r m e d ia te compound formed i s
so s t a b le th a t th e r e i s c o n s id e r a b le r e d u c tio n i n th e number o f magnesium
o x id e m o le c u le s a v a ila b le and th e r e fo r e e x c it e d in th e f lam p.
Leyton ( 8 ) ,
h as proposed a d eg ree o f d i s s o c i a t i o n r a th e r than a " d if f e r e n t .type o f
em issio n to e x p la in th e reduced e m is s io n .
The second p o s t u la t e o f a b so r p tio n or em issio n o f energy e s t a b lis h e s
an i n t e r e s t i n g com parison when f r e e e n e r g ie s o f fo rm a tio n a re c o n sid e r e d .
A l i s t i n g o f th e a n io n s u sed i n t h is i n v e s t i g a t i o n and arranged i n t h e .
- 29' ord er o f t h e ir d e c r e a sin g f r e e e n e r g ie s o f fo r m a tio n , (in c r e a s in g s t a b i l ­
itie s )
show them to f o llo w the o r d e r , •-p e r c h lo r a te , - n i trains, -Chlrpride, a r -.
s e n a te , chrom ate, s u l f a t e , and p h o s p h a te .. The
v a lu e s rangfe from - 1 0 ,7
k c a l. f o r p e r c h lo r a te io n to - 2 l|1 .0 k c a l. f o r phosphate i o n .
"This order i s
n o t ic e a b ly c o n s is t e n t when th e s e a n io n s a re arranged in ord er o f t h e ir
a b i l i t y - t o d ep ress 'th e 1^ n t e n s i ty . of-ma-gnesium-"emission, "Figure. # 2 .
A lthough'
't h e s e AF0 v a lu e s a re f o r 25° ' C , . the ord er might- w e ll be p reserv e d to much
h ig h er tem p era tu res.
The maximun• tem peratures'-determ ined: b y L urie & Sherman
(1 0 )j f o r "oxy —
arce L ylene' flam e "was IltlO0 K and 2933° K f o r oxy—
hydrogen fla m e .
To a r r i v e - a t a c o n c lu s io n th a t a b so r p tio n o f en ergy u p on-d ecom p osition o f
th e a n ion s in th e flam e i s r e la t e d or c o n s is t e n t to t h e ir r e s p e c t iv e f r e e
-en ergies o f "formation;, on e sh ould c a l c u l a t e thre-free^ e n e r g ie s o f forma­
t io n and th e f r e e e n e r g ie s f o r w hatever r e a c t io n occu rs w ith in th e fla m e a t
th e e x c i t a t io n tem p era tu re.
There a re f a c t o r s however t h a t r e s t r i c t s the
e x c i t a t io n tem perature from r ea c h in g th e Maximum v a lu e s o f ap p roxim ately
3000° K.
The v e l o c i t y o f th e s o lu t io n through th e a s p ir a t o r , th e b i -
products" form ed i n th e fla m e , th e-v a p o r -p r e s s u r e s , th e p r o p o r tio n o f oxygen
to f u e l and th e n a tu re o f th e burned and unburned g a se s i n th e 'flame a l l
"would in f lu e n c e th e a c t u a l e x c i t a t io n tem p era tu re.
Thus f r e e energy c a l­
c u la t io n sh ou ld add c o n s id e r a b ly to th e u n d erstan d in g o f what happens w ith ­
in" th e fla m e," ev en though -maximum flam e tem peratures were n o t u s e d - i n the
c a lc u la tio n s .
-
-
The a b so r p tio n o f en ergy would b e s t e x p la in th e ten d en cy , p a r t ic u la r ly
n o te d "with chrom ic a c id , f o r i n t e n s i t i e s to r e tu r n to th e o r i g in a l mag­
nesium sta n d a rd v a lu e , a f t e r th e i n f l e c t i o n p o in t had been rea c h e d . • i t has
t
— 30 —
been o b served th a t o th er a c id s ten d to r etu rn to th e o r i g in a l .in t e n s i t y .
v a lu e o f th e stan d a rd , b u t o n ly a f t e r th e c o n c e n tr a tio n o f th e a c id was i n ­
c re a se d beyond th e c o n c e n tr a tio n l i m i t s p r e se n te d in t h i s work.
T t may
w e ll be th a t a t th o s e a c id c o n c e n tr a tio n s beyond th e i n f l e c t i o n p o in t,
an oth er r e a c tio n o ccu rs w hich i s ex o th erm ic, and e v e n tu a lly p ro v id es s u f ­
f i c i e n t en ergy to e x c i t e a l l o f th e "magnesium..
■-
I t i s r e a so n a b le t o assume th a t n o t any one o f th e proposed b eh a v io rs
i s o p e r a tin g in d e p e n d e n tly , by.t th a t a com b in ation o f two or a l l th ree con­
t r ib u t e in f lu e n c e on th e f i n a l b e h a v io r .
Tn ord er to fu r th e r i n v e s t i g a t e flam e photom etry b eh a v io rs from a
t h e o r e t i c a l p o in t o f v iew , some knowledge o f fo u r s it u a t io n s would appear to
be n e c e s s a r y .
F i r s t , a more a c c u r a te knowledge o f th e a c t u a l o p era tin g
flam e tem peratures,.
Second, more in fo r m a tio n in t o th e co m p o sitio n o f the
compounds formed and t h e ir in t e r a c t io n w ith in th e s e tem perature ,ra n g es.
T h ird , what a re th e components i n th e flam e a t e x c i t a t i o n , and what in ­
f lu e n c e do th e y have in s ig n a l to background r a t io ?
"Fourth, What i s th e
spectrum o f each a cid ?
J
/
— 31 ~
V I I I . SUMMARY _
I n the" flam e photom etry d eterm in a tio n o f .magnesium, a n io n ic e f f e c t s a re
pronounced and m ust be accou n ted f o r i n a c c u r a te q u a n t it a t iv e m easurem ents.
S ig n if i c a n t e f f e c t s o f p h o sp h a te, s u l f a t e , a r s e n a te and' p o s s ib le b o ra te io n s
sh ould be w atched fo r t h e ir d e p r e ssa n t a c t io n , whereas p e r c h lo r a te io n w i l l
enhance th e re a d in g s o f th e magnesium fla m e e m is s io n .
C om binatiops o f one ■
or more a n io n s in th e magnesium system w i l l be c o m p e titiv e and c o n t r o lle d by
r e l a t i v e s t a b i l i t i e s and c o n c e n tr a tio n s o f th e a n io n s .
- 32 IXo ACIQiDWLHJGfflEHTS'
-
The au th or w ish e s to ta k e t h i s o p p o r tu n ity to ex p ress h i s a p p r e c ia tio n
and thanks to Graeme L . B aker, D r. Leon H. Johnson, D r. C h arles N. Caughlan,
th e r e se a r c h s t a f f and g e n e r a l f a c u l t y f o r t h e ir p a tie n c e and, s u g g e stio n s
i n c u lm in a tin g t h i s r e p o r t .
- 33 X. 'LITERATOEE"-CITED
(1 )
Baker, G.L. and_Johnson, L .H ., A n a l. Chem. .26?h6$} - (19$b)
(2 )
B arn es,. R .B ., e t a l . , I n d . Eng.- Chem. A n a l. E d ., 17,. 6 o 3 , (UpbS)
(3 )
B erry, J'.W., C h a p p ell^ D .G ., and B arnes, ""ReI . , I n d . 'Eng. 'Chem.,
A nal. E d ., 1 5 , 19 ,---(1916)
(i|)
-
C h lo la k , J . and Hubbard,TDJM., T nd. Eng. Them. A nal. E d ., "16, "728
(19l4ll)
-
(5 )
C o o ley , M .L ., C erea l Chem., 30", 3 9 , (1933)
(6)
D enson, j . R . , -J. B i o l . Chem. 20 9 , 2 3 3 /( 1 9 3 1 )
(7)
F i e l d s , .M ., e t a l . , S o i l S c i . , 7 2 , 219, (1931)
(8)
Ley-ton, L ., A n a l y s t ,'7 9 , L97, (193b) •
(9)
Lundegardh,- H ., "Die q u a n t it a t iv e sp e k tp a la n a ly se der Elements'",
Jen a, G ustav F is h e r , P a rt I , 1 9 2 9 ; P art IT , (193|i)
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L u r ie ,"H.H ., Sherman, "G.W., In d . Eng. Chem. 2 3 , ii-Oit,- (1933)
• ■
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W est, . P.W ., F o l s e , P , , and Montgomery, D ., .A nal. Chem. 22, 66?, (195.0)