-I
VIC
Y
THE CORROSION OF DURIRON ANODES
BY
CHARLES W.
DINAN
COURSE XIV -1927
7
Cambridge,
October 15,
Mass.
1927
Prof. A.L.Merrill,
Secretary of the Faculty,
Massachusetts Institute of Technology,
Cambridge, Mass.
Dear Sir:In partial fulfillment of the requirements
for the degree of Bachelor of Science in Electrochemical
Engineering, I submit the accompanying thesis.
Respectfully submitted,
Charles W. Dinan
10 219
ACKNOWLEDGMENT
The writer wishes to acknowledge the
advice and other helpful suggestions of
Prof. M.
deKay Thompson.
TABLE OF CONTENTS
PAGE
Object
1
Introduction
1
Method - Apparatus - Procedure
7
Discussion
15
Conclusion
17
Results
19
Bibliography
24
Appendix
25
INTRODUCTION
OBJECT:
The object of this investigation is to
determine the advisability of using durion anodes
in certain electrolytic oxidations.
THEORY:
The use of platinum electrodes has been
very extensive and completely satisfactory,
from the scientific viewpoint, when unattackable
electrodes are required.
However, from the
economic viewpoint, the use of platinum is
objectionable because of its excessive cost, and
the resulting value of goods tied up.
Therefore,
from the start of industrial electrochemistry,
research workers have been trying to discover
a substitute for platinum that will be both cheap
and practically unattackable.
Various metals
or alloys have been found satisfactory under
certain conditions but none have been found that
may be used for as many different purposes
as platinum.
Since the problem is primarily
one of corrosion, an explanation of the theory
of corrosion brings to view the various factors
which play a part in this investigation.
The electrochemical theory is how
generally accepted as the one which best explains
the mechanism of corrosion.
-1-
Since the test is being made on an alloy of
silicon and iron, the theory may be specifically
applied to the metal.
According to the explanation by Speller
in "Corrosion", "Iron, like all other elements,
has a definite, inherent tendency to go into
solution when placed in contact with water.
Iron can enter solution only by displacing
some other element already in the solution.
Hydrogen is the element usually plated out.
This hydrogen gathers on the surface of the iron
in the form of a thin, invisible film.
The
presence of this film obstructs the progress
of the reaction by insulating the metal from
the solution.
In order that corrosion may
proceed, the film must be removed.
This may be
removed by depolarization, combination with
oxygen to forn water, or it may pass off as
gaseous hydrogen. "
Corrosion reactions:
Fe(metal)+2H (ionic) = Fe++(ionic) + 2H (atomic)
Removal of hydrogen:
2H (atomic) + 1/2 02 (dissolved) =
H20 (water)
2H (atomic) = H2
-2-
(molecular).
In all electrolytic cells, an oxidation
takes place at the anode.
Since the primary
corrosion reaction is the oxidation of the metal,
the anode is the more severely attacked.
Therefore,
the formation of an unattackable anode is the
object of men working in this field of research.
The effect of alloying various
quantities of silicon with iron was first
studied
systematically by Jouve, in France, in the year
1900.
The possibilities of this combination were
borne out owing to the fact that when conducting
analyses of steel-silicon alloys, considerable
difficulty was experienced in the attack of acid
upon these metals.
After having prepared a
series of silicon steel alloys for the purpose
of acid resisting, progress in this investigation
was held up because of the unsatisfactory
physical nature of the metal.
However, in 1907,
Jouve stated that-he had been successful in
overcoming to a very great extent the difficulties
inherent in the preparation of these alloys.
Numerous castings and vessels were produced with
considerable satisfaction although the greater
part of these pieces were of comparatively small
size.
-3-
90-10001iial-
__9
Later,
in Germany,
"Neutraleisen"
was produced for the purpose of making castings
The
to withstand nitric or sulphuric acid,
production of "Neutraleisen" met with many
disappointments, finally resulting in the
abandonment of its manufacture.
The develop-
ment of the electric furnace has proved a
valuable aid to the satisfactory commercial
production of alloys of ferro-silicon and
consequently these alloys are now produced in
In the
good quality and in good quantities.
year 1917, Kowalke, in America, ma4e considerable
research to determine the resistance to corrosion
of alloys of iron and silicon.
He found that
when silicon is present in a lesser quantity
than 12%, it does not promote a satisfactory
resistance to corrosion.
Also, when the silicon
content of the alloy reashes 16% or upvards
the acid resisting quality again falls.
konsequently, in producing these high silicon
irons for acid resisting, one is compelled to
work between fairly narrow limits.
The most
suitable alloys have been found to be those
containing between 13% and 15% of silicon.
The metal is extremely hard and melts at about
12500 C.
Owing to its hardness it is
impossible to machine it in any other way
-4-
.1
than by grinding with high-speed abrasive wheels.
There are several recognized manufacturers
of high silicon irons for resisting acids both,
in this country and in Europe, and each has its
separate trade brand.
In this country, the best
brands are "Duriron" made by the Duriron Company,
I-layton,
Ohio, and "Corrosiron'i,produced by the
Bethlehem Foundry & Machine Co., Bethlehem, Pa.
In Europe, the most important alloys go under
the nanes of
"Ironac",
"Tantiron",
and
"Narki" metal.
Since high silicon iron was developed
primarily as an acid-resisting alloy, there
is no reason to assume that this alloy is
adaptable to other conditions of corrosion.
On the contrary, when the alloy is placed
in contact with strong alkaline solutions,
it
is appreciably attacked and is vevj unsatisfactory
as a base-resisting metal.
The base attacks
the silicon forming silicates, thus ruining
the structure of the alloy.
However, it is an
interesting problem to study the corrosion of
high silicon iron in certain electrolytic
oxidations, and to determine the inhibiting
effect of the silicon under conditions widely
divergent from those for which the alloy was
intended.
Therefore, a study was made of the
-5-
electrolysis of various solutions using duriron
anodes.
REVIEW OF LITERATURE
Some work has been done relative to the
corrosion of duriron in acid solutions but very
little work has been published concerning the
behavior of duriron anodes.
Kowalke made an
extensive study of the acid corrosion of iron
silicon alloys, the results of which he presented
to the American Electro-Chemical Society in
1917.
Fink and Eldridge, in a paper presented
to the American Electro-Chemical Society in
1921, mentioned the use of duriron anodes by the
Chili Exploration Company at its Chuquicamata
copper refining plant.
More information about
the results obtained by this company are
lacking due to .its failure to publish any work
which was carried out in this field.
In T922,
J.M.Cosgrove and J.S.Sarros performed a thesis
at the Massachusetts Institute of lodhnology
on the corrosion of duriron anodes in NaOH
solutions of various concentrations.
They
arrived at the conclusion that the rate of corrosion
increases considerably with an increase in
temperature.
Their results also show that
there is an increase in the rate of corrosion
as the concentration of the NaOH is increased.
-6-
However, they did not complete any work on
electrolytic oxidations using duriron anodes.
Therefore, any commercial application of their
Since 1922, no work in this
work is lacking.
field has been published.
METHOD
-
APPARATUS -
PROCEDURE
The apparatus used in this investigation
consisted of a sour.ce of electromotive force,
115V D.C., a 15a ammeter voltmeter, 3v-15v-15Ov,
rheostats,
and a series of four cells.
The four
cells were placed in a zinc-lined tank about
six feet long, and a cross-section about tem
inches square and open at the top.
The cells
consisted of one or two liter beakers, a
cylinder of sheet lead as cathode and an anode
of duriron supplied by the Duriron Company of
tayton, Ohio.
The series of four cells were
placed across the 115 volt D.C.
supply with
the ammeter and rheostats in series.
The
voltmeter was fitted with long leads to obtain
the voltage drop across each cell.
The tank
was filled with water to maintain a fairly
In the case of low
constant temperature.
temperatures, cold water was circulated through
the tank and in the case of higher temperatures
the warg bath was kept stationary, the heat
-7-
MI4
given off by the passage of the current compensating
for the heat lost to the atmosphere.
In this investigation, three different
oxidations were tried.
First, a solution of
potassium chlorate was subjected to electrolysis
for the purpose of producing potassium perchlorate.
Next, a solution of chrome alum in sulphuric
acid was electrolyzed to form chromic acid.
Lastly, a basic solution of potassium manganate
was oxidized for the production of potassium
permanganate.
In the first case the procedure
according to Elbs was followed with slight
variations.
The electrolyte consisted of a
saturated solution of KCLO 3 at room temperature.
In order to keep the solution saturated, a
cloth bag filled with solid KCLO3 was suspended
in the solution.
A duriron anode and lead
sheet cathode were used instead of the platinum
electrodesrecommended by Elbs.
The cells
used were one liter glass beakers.
No
diaphragm is necessary in this run.
The four
cells were placed in series in a bath of
circulating cold water.
-8-
M
The electrolytic oxidation of chlorates
to perchlorates depends on the reaction,
2 CLO3 + H20 = HCLO 4 + HCL03 ,
whereby 2 discharged chlorie/acid ions unite with
water to give one molecule of perchloric acid
and one molecule of chloric acid, which form salts
with the alkali produced at the cathode.
This
reaction is confined to low temperature.
At
warmer temperatures, the transformation of the
acid radicals occurs,
2 CLO 3 + H20 = 2 ICLO 3
+
0
and the evolution of oxygen replaces the
oxidation of the clorates.
In the first
run, the current was
adjusted to about 8 amperes and the electrolysis
According
was allowed to continue over-night.
to Elbs, when the experiment has been in progress
some time, the electrolytic becomes saturated
with KCLO, and fine crystals of perchlorate
fall from the anode to the bottom of the vessel.
Actually, however, the electrolyte soon becne
badly contaminated with iron rust and no
crystals of perchlorate appeared.
Oxygen was
evolved continuously during the run.
After
the run the solution was treated with H 2 SO,
in just sufficient quantities to dissolve
-8-
-1
the precipitate of ferrous and ferric hydroxide.
When this was done nothing else remained in the
liquid as solid matter giving further proof of
the absence of KCL04 .
A second test was made with
the same solution having a current density about
double that of the first test.
This increase
in current density raises the anode potential and
presents a possibility of obtaining a yield of
KCL04.
In this case, it was impossible, with
the means available, to keep the temperature below
250 C., as recommended, owing to the heat evolved
by the I2 R losses in the cells.
However, this
procedure met with no more success than the
first.
Therefore, it was decided to leave the
chlorate solution and turn to the chrome alum
electrolysis.
The oxidation of chromiumsulphate
to chromic acid is carried on in an electrolyte
consisting of 200 grams chrome alum, KCr(SO)z
+ 12 H%0, dissolved in hot water, 150 cc
concentrated sulphuric acid and the solution
is made up to 1000 cc.
The cells were two
liter beakers having a lead sheet cylinder as
cathode,
duriron anodes,
and a porous pot
containing the anode and anode solution.
The
porous pot is used to prevent the mixing of
the anode and cathode solutions.
-9-
The electrolysis
test with a current
was carried out in the first
density at the anode of about 2 amperes per 100
sq.cm. at a temperature of around 500 C.
The cells were surrounded by a hot bath and the
heat developed in the cells was'enough to maintain
a fairly high temperature although it varied
considerably during the tests.
During the run,
302 was evolved continuously from the anode, its
7
(
/
/jJ
N
presence being readily detected because of its
pungent odor.
The process of oxidation is
expressed by the equation.
Cr
2
(SO4)
3
+3 SO,
+ 6 H20 = 2 CrOs + 6 H 2 SO 4
At the cathode hydrogen is evolved almost
quantitatively.
The yield is determined by ti-
trating samples of the anode solution with ferrous
ammonium sulnhate and potassium permangate,
This titration proved to be most difficult
because of the various color changes which occur
as the end point is approached.
The anode
solution, even after dilution, imparts a strong
The green color
green color to the liquid.
persists after adding the excess ferrous
ammonium sulphate but on titrating back with
the potassium permanganate, the green first
slowly changes to blue, then to purple, and
when excess permanganate has been added, the
solution turns dark red.
After titrating a
number of samples from the same anode solution
-10-
the one which appeared to be the most representative
was chosen.
This,
however,
showed no yield.
Another run was made with this solution
having a current density about four times as great as
case.
in the first
This run showed no better
results and there was considerable increase in the
corrosion of the duriron anodes.
these runs,
After each of
the anodes were covered with a soft
gray coating which was removed by rubbing lightly
with emery paper before drying and weighing
the anodes.
Pitting was observed in only a few
places on the metal oieces.
For the most part,
corrosion was fairly uniform over the entire
surface.
However, the anodes soon lost
the smoothness that they possessed at first and
became quite rough wherever they were in contact
with the solutions.
The next electrolysis tried was the
oxidation of potassium manganate to permanganate.
There was very little information available
cohberning this process but a fair 'idea of the
procedur-e was obtained from a thesis by
Schabacker in 1916 on the electrolytic production
of potassium permanganate.
The procedure was varied with the view of
determining the adaptability of duriron anodes
rather than producing permanganate commercially.
-11-
Three electrolytes were made up, the first being
about one normal in sodium hydroxide, the second,
one-half normal, and the third, one-sixth normal.
Forty grams of potassium manganate were then
added for each liter of solution.
The cells con-
sisted of sheet lead cathodes, duriron anodes,
pProus pots, and two-liter beakers as vessels.
The three cells were then placed in series across
115 volts, the current being regulated by series
resistances.
The cells were placed in a tank of
circulating cold water during the electrolysis
A current density of
to prevent excess heating.
about 2 amperes per 100 sq.cm. was used and the
oxidation was carried out for two and one-half
hours.
A slight evolution of oxygen was
perceptible at the anode during the electrolysis.
After the run the anodes were covered with a soft
brown coating which was rubbed off before weighing.
Schabacker, in his investigation determined
the current efficiency by means of the deficiency
in oxygen evokved at the anode.
This, however,
was deemed inadvisable because of the great
possibility of error.
Therefore, an analysis
of the solution was made.
First, the insoluble
matter in the potassium manganate was determined
by taking a weighed sample, dissolving, filtering,
and igniting the residue.
From the weight of the
-12-
residue, the percentage of insoluble matter in the
manganate may be found.
Direct titration of
the anode solution after electrolysis was impossible
since the reduction with ferrous sulphate, must
be carried on in an acid solution to prevent the
formation of MR0B.
Moreover, the direct addition
of sulphuric acid would result in the conversion
of the manganate to permanganate and manganese
dioxide according to the reaction.
3 Ka MnO4+2 H2 SO, = 2 K mnO,+ 2 K2SO4 + MnO2 + 2 H 2 0.
Therefore, the analysis was carried out as follows:
The OH concentration of a sample of the amode
solution was determined by adding anexcess of
Cd SO
solution.
This precipitated cadmium
hydroxide which came down first as a brownsolid,
showed the presence of impurities.
After filtering,
the residue was redissolved in dilute sulphuric
acid and reprecipitated with sodium hydroxide.
This time the cadmium hydroxide came down as a
white solid.
The solution was again filtered
and the residue dried and weighed.
From the
weight of the cadmium hydroxide and the volume
of the sample taken, the OH concentration was
calculated.
-12-
Another sample of the anode solution was
treated with excess sulphuric acid.
The resulting
solution is treated with excess ferrous ammonium
sulphate and titrated back to the end point with
a solution of K MnO* of known strength.
Lastly,
the acid concentration of the final solution
is found by neutralizing with a solution of
sodium hydroxide.
From the acid concentration
at the end, the OH concentration of the initial
sample, and the amount of acid added to the
solution, the acid disappearance may be determined.
The acid thus lost is the acid used to cohvert
the potassium manganate to permanganate according
to the preceding reaction.
Therefore, from the
total permanganate present, and the. permonganate
formed by the acid reaction, it is possible to
determine the amount of K MnO 4 formed during
the electrolysis and thereby, the current
efficiency may be calculated.
Because of the
lack of time it was impossible to run checks on
the potassium manganate oxidations.
The anodic potentials of duriron
was then measured in each of the solutions
investigated.
One of the anodes was covered
with pitch leaving a rectangular opening of a
definite area on one side.
-13-
The various cells
used were again set up and the variation of anode
potential with currentdensity was measured.
The current through the cells was varied by means
of rheostats in series.
The anode potentials
were measured by the usual slide wire method
except that a potentiometer was substituted for
the slide wire.
The temperature of the solutions
were kept as nearly alike as possible to the
temperatures under which the tests were made.
-14-
"M
DISCUSSION:
The electrolytic oxidation of KCLO3 proved
unsuccessful under the conditions of this investigation
but better results should be obtained if the conditions
were altered.
The oxidation should be carried out
in a cold solution instead of at room temperature.
Therefore, if a cooling coil were immersed in the
cell solution it might be possible to obtain a'
yield of K CLI .
However, some provision must be
made for keeping the iron rust out of the solution
since this greatly decreases the current efficiency
and contaminates the product.
The solution could
be made slightly acid to prevent the formation
of ferrous and ferric hydroxide but the acid
addition would increase the corrosion of the anodes.
Also, the increased quantity of iron in the
solution would materially affect the current
efficiency.
In view of these facts it
is not
considered feasible to use duriron anodes for
the electrolytic production of K CLO4.
The attem-pt to produce chromic acid
electrolytically using duriron anodes met with
still less success than the first oxidation tried.
-15-
Not only was there no yield of chromic acid, but
the corrosion rate of the anodes was so large that
it would be impractical to carry out such an
oxidation even if the acid were produced quantitatively.
The electrolytic production of K MHO,
was successful to a limited extent with the duriron
anodes.
However, the current efficiency was found
to be extremely low.
This value could be
increased by altering conditions.
For example,
an excess supply of K2 MnO4 should be in contact
with the anode solution to replace that portion
The continued formation
that is oxidized to KMNOt.
of potassium permanganate will soon saturate the
solution and crystals of the solid will separate
out.
The procedure followed in the analysis of
the anode solutions became much more involved
than was at first
expected and considerable
experimental error was consequently introduced in
the result.
In fact, the last part of the work
became a complicated problem in quantitative
analysis rather than in electrochemistry.
A
simpler procedure should be mapped out and followed
if more work is to be done in this field.
-16-
The measurements of the anode potentials are likely
to be somewhat in error due to a slight difference
in potential between one terminal of the 115 volt
supply which was used to electrolyze the cells,
and a terminal of the 20 volt battery which was used
to send the current through the potentiometer.
CONCLUSIUNS:
In view of the results of this investigation,
the use of duriron anodes is found to be entirely
unsatisfactory in &44i- solutionsA
In neutral
solutions, the rate cf corrosion is considerably
lower but, unless a high enough current efficiency
can be realized, the use of duriron anodes cannot
be recommended.
In basic solutions, the corrosion
is very much lower than in neutral solutions.
Therefore, duriron anodes may be used satisfactorily
provided the current efficiency in the process is
high enough to make it commercially successful.
The loss due to corrosion in alkaline
solutions decreased appreciably as the OH ion
concentration was increased.
This decrease will
probably meet a limiting value when the solution
gets so strongly basic that it
of the alloy forming silicates.
-17-
attacks the silicon
It would be
interesting to perform some experiments along this
line to see if such a limiting value is approached,
and if so, where.
It was also found that the rate
of corrosion increases considerably with an
increase in the current density, and also with
an increase in temperature.
Therefore, in order to
carry out an electrolysis with duriron electrodes,
the conditions favorable for a small loss of the
anode consist of a high OH inn concentration in
the solution, low current density and low temperature.
-18-
RESULTS
Run #1
KCL03
solution
Current density = 4.7 amperes
per 100 sq.cm.
Average temperature = 22.50 C.
Rate of corrosion of anodes per faraday.
#1
#2
.225 g
.257 g
Current efficiency
Run #2
KCLO3
#3
#4
.260 g
.251 g
= 0
solution
Current density = 8.25 amperes per 100 sq.cm.
Average temperature = 280 C.
Rate of corrosion of anodes per faraday.
#1
#2
#3
#4
.480 g
.452 g
.477 g
.484 g
Current efficiency = 0
Run #3
Chrome alum solution
Current density = 4.88 amperes per 100 sq.cm.
Average temperature = 550 C.
Rate of corrosion of anodes per faraday.
#1
#2
#3
#4
2.49 g
2.63 g
2.81 g
2.57 g
Current efficiency = 0
-
19 -
Run #4
Chrome alum solution
Current density = 17.6 amperes per 100 sq.cm.
Average temperature = 60.50 C.
Rate of corrosion of anodes per faraday.
#1
#2
#3
#4
3.38 g
3.06 g.
3.45 g
3.22 g.
Current efficiency = 0.
Run #5
Potassium manganate solution
Current density = 2 amperes per 100 sq.cm.
Average temperature
= 25.50 C.
Rate of corrosion of anodes per faraday.
#1
#2
#3
1 Normal HaOH sol
1/2 normal
NaOH sol.
.160 g.
1/6 normal
NaOH sol.
.267 g.
#1
#2
#3
1.65%
1.01%
.75%
.027 g.
Current efficiency
-
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ECHNOLOGY BRANCH
ARF COOPERATIVE SOCIETY, CAMBRIDGE
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BIBLIOGRAPHY
1.
Dr. Karl Elbs, Electrolytic Preparations,
p. 17-19, 33-35.
2.
lhorp: "Outlines of Industrial Chemistry,"
p. 299.
3.
Kowal1e;American Electrochemical Society,
1917, p. 206.
4.
The Effect of Silicon on the Electrical
Properties of Iron. Chem.Abs. 4.1972.
5.
S.J.Tungay; Acid-Resisting Metalsp. 21.
6.
H.P.Talbot; "Quantitative Analysis",
p. 68.
7.
Cosgrove and Sarros; "The Corrosion of
Duriron Anodes", M.I.T.Thesis, 1922.
8.
Schabacker; "The Electrolytic Preparation
of Potassium Permanganate', M. I.T.Thesis,
1916.
9.
F.N.Speller "Corrosion",
- 24 -
p.
9.
APPENDIX
-25-
CALCULATIONS
Run #1
Total coulombs = 23.75x3600x8=684,000 coulombs
684,000
= 7.1 faradays.
-------
96,500
8
Current density = ---170
100 = 4.7 amperes per 100
sq.cm.
Loss per faraday
1.
2.
1.822
----- = .257 g
7.1
1.599,
-----7.1
3.
1.786
------7.1
4.
1.844
----- = .260 g
7.1
= .225 g
=-.251
g.
Run #2
Total coulombs
5 x 3600 x 14 = 252,000 coulombs
252,000
--------
= 2.61 faradays
N
96,500
14
100 = 8.25 amperes per
Current density = ---
100 sq.cm.
170
Loss per faraday
2.
1.
1.255
-----2.61
3.
1.179
= .480 g.-------2.61
4.
= .452
g.
1.244
------2.61
1. 263
------2.61
-
=.484 g.
26 -
= .477 g.
Run #3
Total coulombs
2-2/3 x 3600 x 8.3 = 79600 coulombs
79,600
-------96,500
.826 faradays
8.3
Current density = ---170
100 = 4.88 amperes per
100 sq.cm.
Loss per faraday.
2.
2.058
-----.826
= 2.49 g.
3.
2.172
------
2.319
= .263 g.
.826
4.
------
= 2.81 j
.826
2.123
------ = 2.57 g.
.826
Run #4
Total coulombs
1.5 x 3600 x 15 = 80200 coulombs
80,250
------96,500
= .83 faradays
15
Current deMsity = ---
100 = 17.5 amperes per
100 sq.cm.
85
Loss per faraday
2.807
-----.83
3.
2.874
2.
2.538
= 3.38 g.
------
= 3.06 g.
.83
2.670
4. ------- = 3.22 g.
.83
-
27 -
------.83
-
3.45 g.
Run #5
Total coulombs
2.5 x 3600 x 2 = 18,000 coulombs
18,000
--------
.187 faradays
96,500
2
100 = 2.0 amperes per
Current density = ---
100 sq.cm.
100
Loss per faraday
2.
1.
.005
-----.187
= .027 g.
3.
.030
----.187
160 g.
-
28
-
.050
---.187
=.267 g.
anode solutions.
Analysis of K 2 MnO
Sample of 100 cc anode solution taken
Excess CdSO
added
Weight of Cd(OH)2
precipitate
1/2 N
1 N.
7.450 g.
13.596 g.
2.487 g.
Normalities of solutions
13.596
------146
10 = .931
7.450
------ 10 = .510
146
2.487
------- 10 = .170
146
Sample of 100 cc anode solution taken.
100 cc 4.9 N HSO, added
Titrated with FeSO,
1 N
1/2 N
1/6 N
174 cc Fe S0,4
180 cc FeSO 4
194 cc FeSO6
Equivalent of .0988 N KMnO 4
201 cc
187 cc
181 cc
Grams of KMNO 4
.566
.585
g
HSO,
g
.628 g
disappearance
.74
.31 cc
Mols K MnO
1.05 cc
cc
from acid
.000514
.00181
.00257
.286
.406
g.
.222
g.
Grams KMnO 4 from acid
.081
g.
g.
KMNOI prodtced by electrlysis
.485 g
.299
g.
-
29 -
Current efficiency in KMNO* production
Time = 2.5 hours
Current = 2 amps.
Coulombs = 2.5 x 3600 x 2 = 18000
18000
Faradays = ---------
= .187 F
96500
Theoretical production
.187 x 158 = 29.5 grams KMNO,
Current efficiency
1 N.
.485
------- 100 = 1.65%
29.5
1/2 N.
1/6 N.
.299
-----29.5
-
100 = 1.01%
.222
---29,5
30 -
100
75
Dimensions of anodes
6" x 2" x 1/2"
Run #1
Depth'of anodes submerged = 5.5# inches
Electrolyte:
Time
Saturated solution of KCL03
V1
V2
V3
V*
Current
Temp.
11:15 AM
7.40
7.40
7.55
7.93
7.50
20.00 C
1100 PM
7.38
7.40
7.53
7.92
7.60
21.0
3:00 PM
7.38
7.38
7.52
7.90
7.60
22.0
5:00 PM
7.38
7.38
7.52
7.90
7.60
22.0
6:00 PM
7.37
7/*38
7.52
7.90
7.65
22.5
9:00 PM
7.33
7.34
7.47
7.85
8.45
24.0
11:00 AM
7.33
7.34
7.47
7.85
8.60
24.0
W7eight of anodes
1
2
4
3
Before
370. 892 g.
388.639
372.216
383.714
After
369.070
387.040
370.372
381.928
1.822
1.599
1.844
1.786
Loss
Average temperature = 22.50 C.
-
31 -
Run #2
Depth of anodes submerged = 5.5
Electrolyte:
Time
inches
Saturated solution of KCLO3
V1
V2
V.3
VO,
Current
Temp.
10:00 AM 11.25
11.10
12.20
11.70
14.00
250 C
11:00 AM 11.30
11.18
12.30
11.75
14.00
28
11.20
12.34
11.80
14.00
30
1:00 PM 11.34
11.25
12.35
11.82
2:00 PM 11.35
11.27
12.35
11.84
14.00
31.5
3:00 PM 11.35
11.27
12.36
11.84
14.00
31.6
12:00 M
11.32
31
14.00
Weight of anodes
1.
4.
3.
2.
Before
369.070
387.040
370.372
381.928
After
368.815
385.861
369.128
380. 665
1.255
1.179
1.244
1.263
Loss
Average temperature = 280 C.
-
32 -
#3
Run
Depth of anodes submerged = 5.5 inches
Electrolyte: 200 grams chrome alum, 15 0 cc concentrated
HzSO, per 1000 cc. of hot aqueous solution
Time
V1
V2
6:20 PM
3.80
6:50 PM
V3
V4
Current
3.70
4.10
3.95
8.30
470 C
3.65
3.60
4.00
3.90
8.30
66
7:20 PM
3.70
3.65
4.05
3.90
8.30
59
7:50 PM
3.80
3.75
4.10
3.95
8.30
52
9:00 PM
3.95
3.90
4.20
4.05
8.30
47
Weight of Anodes.
2.
1.
3.
4.
before
369.070
387.040
370.376
381.928
After
367.012
384.868
368.057
379.795
2.058
2.172
2.319
2.123
Loss
Average temperature = 550 C.
Titration of 20 cc sample of anode solution to
determine yield.
KMNO,
Fe NHI (S04) 2 .0542 N.
.0988
36.63 cc
26.48 cc
18.72 cc
16.95 cc
17.91 Uc
9.53 cc
.0542
17.91 x -----.0988
= 9.45
Yield = 0
-
33 -
N
Temp,
Run
#4
Depth of anodes submerged = 3.75 inches
Electrolyte: 200 grams chrome alum. 150 cc concentrated
H2 SO4 per 1000 cc of hot aqueous solution.
Time
V1
12:25
5.05
4.50
4.70
12:55
4.85
4.50
1:15
4.90
1:30
1:53
Weight
V2
V3
V,
Current
Temp.
5.25
15.00
53
4.65
5.15
15.00
58
4.45
4.65
5.15
15.00
62
4.85
4.40
4.60
5.10
15.00
63
4.80
4.30
4.50
5.00
15.00
64
of Anodes.
1.
2.
3.
4.
Before
367.012
384.868
368.057
379.795
After
364.205
382.330
365.183
377. 125
3.807
2.538
2.874
2.670
Loss
Average
temperature = 60.50 C.
Titration of 20 cc sample of anode solution to
determine yield.
Fe (NHi )(SO )2 (.0542 N)
KMNO 4 (0988 N)
20.95
24.48 cc
9.25
28.42
8.53
15.23 cc
. 0542
15.23 x-----= 5.40 cc
. 0988
Yield = 0
-
34 -
Run #5
Depth of anodes submerged = 3.5 inches
Electrolyte: 40 grams KqMnO4 per liter in one normal,
one-half normal and one-sixth normal NaOH.
Anode solution of 500 cc.
1N
1/2 N
1/6 N
Time
V1
V2
V3
1:10
4.00
5.40
4.40
2
240 C
1:40
4.05
6.20
3.85
2
25
2:10
4.05
6.15
3.85
2
26
2:40
3.95
5.91
3.83
2
26
3:40
3.90
5.70
3.80
2
28
Current
Temp.
Weight of Anodes.
1.
2.
3.
Before
364.207 g.
382.330
365.183
After
364. 202
382/300
365.133
Loss
.005 g.
.030
.050 g.
Average temperature = 25.5* C.
Anode area in contact
with the solutions = 100 sq. cm.
Insoluble matter in K2 MnOj
.
522 grams per 5 grams = 10. 4%
.525 grams per 5 grams = 10.5%.
-
35 -
Run #6
Anode potentials
Area of anode exposed = 18.6 sq.cm.
Standard cell = 1.0159
KCL03
V
solution 200 C
Potentiometer readings
St.
cell
V total
.4092
-. lv
.0965
.0955
+12. 6v
21. Ov
.0965
25. 4v
V anode
Current
-127
1.0047
1.1385
1.537
0
1.5
3.1
4.45
Chrome alum solution 450 C.
St.
cell
.4097
.1414
.1428
.1436
.1437
.1453
V total
V anode
0.20
3.42
3.80
4.08
4.30
4.57
.0400
.8371
.8654
.9067
.9262
.9513
K2 MnO4 solution 1 N.
NaOH
St. cell
V total
V anode
.4120
.29
3.90
4.20
4.90
5.5
6.1
.0327
.1520
.1563
.1689
.1853
.
1799
.4656
.4733
.5081
.5280
.5389
-
36 -
Current
0
1.55
2
3
4
5
200 C.
Current
0
1.6
2.0
3.0
4.0
5.0