vxJ\
r
en,
<p
9
TIE ELECTROLYTIC
PICKLING
INT,
DECi1918J
OP STEEL.
IJ'<~oz/
I
iI
yce
9zra•/
TABIE
OF COJTENTTS.
Introduction
Attempts to Utilize
Page 1
Liquors
Theoryof Electrolytic
Reed's
Pickling
Process
Object of the Thesis
Part 1
3
3
4
Miethodof Investigation
6
Proc edure
7
Data
Part
2
9
2
11ethod of Investigation
16
Procedure
16
Discussion of Results
17
21
Data
Appendix
22
Conclusion
24
Bibliography
25
After iron has been raised to the annealing temperature
and thenr is cooled, it is foundto be covered with a coating
of black iron oxide,
e304, called "mill scale"'.
or on heavy pieces it ia be
may be only a very thin coating,
as
thick
as
This scale
1/32 of an inch, and is usually porous.
The pick-
ling of the steel, the removing of this scale, is a necessary
-preliminaryto its treatment by any process which puts a coating of anyt'hing on the iron; i.e., the galvanizing of
iron or
the enamelling of iron being examples.
As ordinarily carried out, the picI:ling is done by im-
mersing te
object to be
ickled in a bath of sulphuric, hy-
drochloric or hydrofluoric acid.
Wen sulphuric acid is used,
as is most generally the case, the bath should be boiling, and
the acid should be an aqueous solution containing from 3
o acid.
to
The mill scale itself is not attacked by the acid,
but the acid attacks the iron under the mill scale, generating
hydrogen.
The iron being dissolved from under the scale leaves
it loose and in time it falls off, assisted by the pressure of
the hydrogen generated between it and the pure iron surface.
The time of pickling varies from about thirty minutes
four houars, being proportional
to the thickness of the scale
and inversely as the strength of the acid.
be very pure or the time
to twenty-
The acid used must
of pickling is very much prolonged.
The presence of arsenic or another acid, such as hydrochloric
acid, in the pickle has a very retarding effect.*
It is easily seen that the method of pickling
cribed is very eensive;
just des-
rmuch good iron and acid are used to
form a product, FeSO4 , which is practically worthless.
The
scale is not attacked by the acid, but pushed off by brute
force; the force being bought at a very high price by the action of acid on iron.
Not all of the scale is of equal thick-
ness, so one part of the surface is clean and dissolving rapidly
in the acid, while
scale.
the other part is still covered with
It has been found that a voltage of 0.12 volts, tend-
ing to make the iron go into solution, exists between iron and
the scale in a bath of sulphuric acid.**
Thus more iron is
dissolved due to the electrolytic cell formed.
The ideal pick-
ling would be by forming a bath which would dissolve only the
scale; but probably such a solvent will never be invented.
Many attempts have been made to utilize the waste ferrous
sulphate, but thus far no process has been successful.
A small
amount of the pickle liquors are evaporated and the sulphate
A larger
crystallized out to give the copperas of commerce.
amount of the liquors are neutralized with lime, evaporated,
and the product calcined to give the Venetian red of commerce.
Attempts have been made to electrolyze the liquors forming sulphuric acid and iron, but the iron "trees" and short circuits
the cell.
The waste
ickle liquors contain some acid which is
thrown away.
* Storey- Met. & Chem. Eng. 11 - 1913 - Pg 45.
**
Hering- Met. & Chem. Eng. 13 - 1915 - Pg 7
5
.
:
The ordinary methods of pickling are seen to be etrem
-
-
ly wasteful as well as unscientific, and with the view of
correcting these errors numerous attempts have been made toQ
eleQtrolytically
:U
-.
I,'
,
1
q
~o. ~A
-C;e --
4
-l.~a
+Es
In some of these the
pickle the steel.
cvir?R
n-^ A^n
s-&oUa
4ritLaon4
4A
a'hn cn4.~
r^"
a^;,;
eicl+
'O'M
'I
cc cr
1
MM
a'an4'i'sal- w~a
-vvt~e
+,
m
^1 lr
A:M
T he time of pickliag is decreased, but the action is likely to
be irregular, solution of some of the iron always occurs and
the cost of power is greater than the value of
the time gained.
In other methods the metal is made cathode in a bath which is
Aneutral,weakly acid or alkaline; but the scale is removed
very slowly and irregularly.
In the
eutral or alkaline
tion some of the scale is reduced to metallic
iron which is
deposited on the surface of the metal, thus aking
· ;-.
oTiu-
the sr-
face irregular.
The process to be studied in this thesis is based on the
fact that in the electrolysis of any solution reduction occurs
at the cathode.
The iron to be pickled is made the cathode in
an acid bath, and the hydrogen generated reduces the scale to
the lower oxide, which dissolved very readily in the acid.
C. J. Reed patented this process in 1907.
'The patents
say that in the preferred mode of procedure the electrolyte
consists of an aqueous solution of sulphuric acid having a
specific gravity of 1,20; equivalent to an acid content of
27.1%, although good'results may be obtained with solutions
having a specific gravity between 1.15 and 1.25.
concentration
When the acid
is below 9% the action is too slow or irregular
to be of much commercial value.
The anode may be of lead and
.
'
the urrent density at the cathode from forty to seventy am!i
perpe per square foot.
While the process is not limited to
,the.gfse
of an electrolyte of any particular temperature, thi
're
mal of the
scale is found to be effected much more rapid-
and economically at a high temperature. The!
,e-fficiently
e!eetrolyte is preferably maintained at a temperature of 600
,eentigrade. Even higher temperatures may be used, but above
6Q
centigrade there is a greater tendency for the acid to
..
- dissolve metallic iron, and a higher current density is re:
,..ir.ed to prevent such solution.
The first part of the thesis will consist of a compari-
son of the old method of pickling, with Reed's method.
?
This
w.swaa part of a thesis last year, but the comparison was more
favorable to Reed's method than is actually the case in commetal
practice; since any scale which droped
off was made
In
to dissolve and counted as part of the dissolved iron.
this thesis it is proposed to filter off any scale which does
not dissolve at once, and then make a comparison.
The sheets
of metal will be as near alike as possible, and will be
treated until they are considered to be clean.
The amount .of
iron will be found by reducing it all to the ferrous state
and then oxidizing it to the ferric state.
The power used in
the electrolytic method will be measured, and a comparison
made as to costs between the old and the electrolytic methods.
The apparatus to be used in the electrolytic pickling
is
shown in the following pages.
The second part of the thesis. will be to find out if
I.~~~~~~~~~~~~~~~~~~~~~~~~~~·
l~~~~~~~~~~~~~~~~~~1~~~~~~~I
I%* ..
N~~~~~~~h.*
::
5
ferrous sulphate in the solution at the anode exerts any de-:
ipolarizing effect.
The same apparatus will be used as in
the electrolytic pickling, with the addition of a diaphragm
to keep the anode and cathode portions separate.
The volt-
age neestsary to pickle the metal will :be noted when the
anode portion is a pure acid solution, and then a known
amount of ferrous sulphate will be added and the voltage
measured again, keeping all the other factors the same.
anode is of lead and the cathode may be of any material,
preferably iron.
i
.:
The
::iV:
·
ilj(
r:
...-
:
f
f
OF PTEIR ACID PICELIN G OF STL
A CONARiiSO
WITH ELECTROLYTIC ACD
1
B
PICKLING AD
ELECTROLYTIC AAMLI
PBICKLING
1
;o
:The sheets of iron pickled in this 'set of tests were
f
sent from the American Sheet & Tin Plate Company at Columbus,
Ohio, andl-were covered with a thin scale of the black oxide
I,
'c U2
,
/ L
ofiron, e3 4.
Ic
x
The method of carrying on these pickling tests and
making the calculations is as follows:
·;;
.i
:i
-·-
Since the sheets were too large to pickle entire, they
-id
into sizes which would fit easily into the pickling
were ct
cell.
Two samples
gether as
:"i
r?
·
rj
were cut out of the same sheet as near to-
ossible; one sample being used for electrolytic
pickling, and the other for acidi
pickling
.
In order to
:I?:
get a
epresentative
f these sarmples were cut
result, two
9
.from each large sheet and pickled.
One sample was put into the
a
s·
1
d
pickle and the time, current, voltage, etc., noted.
When it
was considered pickled it was taken out and another sample put
-1
i,
in; the same data being taken.
Thus the pickle liquors repre-
;i
a
"
sented as nearly as possible the average of those obtained in
.:i
i:
actual practice.
The current density was figured for each
separate sheet pickled, and. the average current density obtained
ii;
was used in the calculations. From the voltage which -as taken
in every run, the average voltage was found and used in the
lit
.'j
:"
The temperature was taken in every case ana t-hle
calculations.
average temperature found. The areas pickled of all the samples were added together to get the total area pickled.
By
.
· i·i-
ii··
:·.·
'I-
· ·rS.;1.·i.l· .
....
·· · '·:··;-·-·,i
i. -:
'· ·
.. .:
"
i:
:::"
\L
·
i-
.\
rie&ft'cing
the iron in a"' nown volume of the pickle liquor to the
Iferrus
state? an'd titratitg with
poetassiu pern;ig nate solu-
ttion of known strength, the total amount of iron in the solution
and the total area of the samples could be obtained. By weighits area, the area per unit
in:.a sample sheet and measuring
yfeight of sheetcould
be obtained.
Thus knowing the area per
unit;.:weight of sample, and the amount of iron dissolved per
unit of area the amount of iron
could be calculated.
dissolved per ton of sheet iron
Knowing the amount of iron dissolved, the
amount of acid used to combim.e with it could be calculated.
In
the electrolytic pickling, knowing in addition the watt hours
used per unit of area, the total watt hours used to pickle a
Xi
-.
IQI
f a.......... 5
ULI±
bI1 Uo CULL.
± u|
UiO;l
b-I sneeb$
VUaLU.Ut.
Uti QUICa
La-el.
It:5ti
In the electrolytic pickling 1000
W
;
ap, gr. 1.191 were used as a pickle.
Q.c
of sulphuric acid
The pickling
cell
was a
glass eoulometer jar, approximately 15 cm. long by 15 cm. deep
by 5 er. wide, having anodes of
A
.i
lead on each side of the jar,
co-nnectedin parallel and together forming the anodes.
The
iron sheet was immersed in the acid midway between the two
&aodes and made the cathode.
lead
It was held in the solution until
pickling was considered complete.
The surface of the iron after
electrolytic pickling was a silvery white and very clean. After
pickling, the pickle liquors were filtered and analyzed for iron
by running 25
.c. of the liquor through a Jones reductor and
titrating with
lI.nO
4
In this part of the thesis, the iron sheets were simply
dipped in a hot acid solution of 45%
sulphuric acid by weight,
;.'I
i
. iiI
r
::
s
1IL
;r
:·
.
i
:
?-
i
-r%·
;i
Cell used in the electrolytic
pickling of iron
A anodes of lead
B pickle liquor
C cathode of iron
E pickle vat
F liquid in thermostat
Voltmeter and ammeter as .;.,hown.
!,
"'?
.:-
-
.
.
·
":and
removed when they were considered pickled.
There was a
.
foodbit
A
tainer, and this was filtered off to get the iron which was ac-
of scale which collected on the bottom of the acid con-
tually dissolved.
-Thesurface of the iron obtained in this
piC"ling was not as white and clean as the surface obtained in
.the electrolytic pickling.
In this pickling there seemed to be
a very fine mist of black particles deposited on the iron which
darkened the surface, and these did not wash off easily; they
had to be rubbed with the finger before they would loosen and
wash away.
Analysis of the liquor showed that more iron was dissolved
in this method than in the electrolytic method; thus using more
acid.
In addition to this, all of the scale from the samples
was on the bottom of the pickle jar, and in a plant, unless
this is recovered, the.value of the iron thus thrown away must
be charged up,against the acid pickling process.
Alkali electrolytic pickling was also tried, but did not
.
succeed. Anodes of iron had to be used because the lead transferred in alkaline solution. After passing the current for
two hours there was no pickling noticed.
I.
':I
;:
9
Folowring are the data taken on the electrolytic pickling
of the samples sent from the American Sheet & mTin Plate CO:mpany.
Amperes
Current density
Amps ./sq.cm.
2.79
Time- minutes to
pickle each sample 3.0
°O
Temperature-
Area pickled
sq.cm.
','
59-5
156.2
Total area pickled
2.68
2.90
2.66
2.0
5.25
3.0
3.0
65 .o
169o.o
6o.o
182 .0
245.5
169.3
146.0
(sq.cm.)
899.5
1000 c.c.
1.191
Volunme titrated
25 c.c.
c c. of K1n04
12.51
inO4
.0548
59.5
Specific Gravity at 2000
of
.04-71
2.50
Volume of liquor used in pickling
1 c.c.
8.0
8.0
.0325
.0440
.0583
Volts
i
"'';
8.0
8.0
.00578 grams of e
1C
i¢
e'14
. K..&tuw &P4%.&
frt
, '
r
1 gram of sample has area of 3.73
ae,
the-lK
I-$ n/al
-st.
po'
oi
sq.cm.
The 6calculations ae based upon the ollowvingcosts.
Power costs Q20.00 per H. P.
Iron costs 4 per lb.
;4
ji
'oaWC
,
f ?",
r
Ul .e...,
year
,.--,
Sulphuric acid costs 80/ per 100 lbs of .600 Twaddel
,0''
.Ot~
weight,
by
H2S
39.19
1=3 sp. grav;
acid
4
To pickle 1 ton (2000 lbs.) of iron sheets, it costs:
.961 /
Iron lost
.5
Povwer used
Acid used
.8
4.-025
.85 2'
""1
. ....
10
... ·
Folloving are the data taken from the straight acid pickling of the samples sent by the American Sheet & Tin Plate Co.
Time- minutes to
pickle each'samle
Area pickled
sq.cm.
I
Temperature-
:·
3.0
111.00
100.
O°C
4.o
8.0
138.10
6s.00oo13.30
95
99
99.
16s.
5o
98.
Total area pickled
768.9
(sq.ocm.)
-2o Y
v
Specific Gravity at 2000
Volume titrated
c .c.
nO 4
23.04
::
1 c.c. En04
25 c-c.
460 c.c.
Uf
Volume of liquor used in pickling
1.
;·
6.o
3.0
1.04
( 2
= .00578 grams of Fe
1 gm. sample has area of 3.73
s.cm
:·
The cost to pickle 2000 lbs. (1 ton) of iron sheets by the
straight acid pickling is as follows:
Iron lost
1.16
T
Acid used
2 .20
The saving is:
2.200
4-s;7-47 per ton
P:.
:'::·
i:r
The sheets of iron
r·;i
sent from the General Electric
and were samoles of transformer
and so brittle
Companyat Pittsfield,
iron.
8·
blue
that when the samole of iron was bent the scale
seemed to have a large content of silicon
crystalline
;!ass.,
There were two entire-
broke off, showing the pure white iron underneath.
"t.- .
v.ere
kinds of scales;the firstbeing a light
ly different
·.
set of tests
icl1ed in tis
in its formation.
The iron
andawias distinctly
The scale of the second sample
was the usual blue black oxide, non-crystalline, and very adhesive. Directly unaderthe scale on both samples was a layer
:-·
"
a:
Wr.·
_·2i
·
but this was very thin and gave
of oxidethe colorof rust;
--
no trouble in removing.
The cell used in this set of. tests was
I
coated with wax on the
which
itr
·
was used
inside
to keep the hydrofluoric acid
from reacting with the container. Anodes of
lead were used as in the previous experiments.
'Ita,
i
porcelain cup
wvasthe same as in the previous
The procedure
exo er ients.
The pickle liquors used in this set of eeriments
wvere
a mixture of sulph-uric and hydrofluoric acid, because owing to
;-·
the silicious nature o
not
i!:
the
issolve it readily.
electrolytic pickle
but with the
scale, plain sulphuric acid would
The iron
w7hen
it came out from the
was a pure silvery white in each case;
it cameout black.
lain acidpickling
The temperature was kept low in -thi
set of runs because
the cell had to be coated with wax, and a higher temperature
would have melted the wax.
12
An unexpectedly long time was taken to electrolytically pickle
the samples of the first
sheets of iron, thirty-two
minutes
being the average. At the end of ten minutes, however, the
pealehad
become so loosened that it
ould be very easily
brushed off, and if that could be done in a pickling plant
the cost of electrolytic pickling could be cut down enor-
mously.
These samples were not pickled in a
lain acid bath
-
after two hours, and in a bath of only sulphuric acid would
not
:::
pickle at all.
''"'
Is:
I.
.l .
_.
.trl.
i
1
1
··
,-.
e
E..
i
..i,
I
12"
i
i
i
I
i
i
i
13
P
i
tF::
·
Following are the data taken on the electrolytic and
i·j ·
acid pickling of the first samples (light blue brittle scale)
61
sent by the General Electric Company.
-35% by weight sulphuric acid and 2
The solution used was
hydrofluoric acid.
Electrolytic
:-i
Acid
9
Amperes
:.
2.5
2.5
:9
a:
· ·.:--?·Ii
?
:B'
Ei
:%
i
i
·::
·:;
Current Density
Amps. S.cm.
.0o17
3.65
2.90
Time - minutes to
pickle each sample
19
45
Over 120 min.
Temperature - 00
20
20
was not picled
Volts
and samle
c
··.j
;I
Area
-s
·:I
.?.
"
r·
i:
Sa.
ickled
m.
30.6
Total area pickled
sq. cm.
59.0
Volume of liquor used
100 C.c
in pickling
Volwume titrated
1 c.c. of
10G
1.35
O
4
c
5.9
3
r
J
.00578 grams of Fe
-
i gm. of sample has area of 8.25 sq. cm.
.i
i;
?~.·r
*
.~IJ·
,,rR
/"''
(
jiat
-
,,@,,,7"4
,
The costs are as follovws for pickling 1 ton.
Cost of iron
"
1T
acid
"
I
power
.2395,
.*728
,214z0 ..>I
.b85
13.
.535
C1.-413
W ,,
.413 .
No comparison of costs was made here because the sample in
acid did not
pickle.
-&
f' (~
e
?
c.
50 cc.
50 c.c.
c.c. of KLn0O4
::
28.4
f;,
.
t,
.:,
, l,,.,,
f,
14
·.'" ·iAi
Follovring are the data taken on the electrolytiC pickling
of the second samples (dark blue adhesive scale),sent by the
The solution used was 35j by weigh
C-eneralElectric Company.
acid.
by weight hydrofluoric
2
sulphuric acid ad
"
.ff.:
·- ?
3
mt.pere s
7
a,
.o665
Current density
Amps/ sq.cm.
f
Voltz
3
3
.0695
.0705
.0723
3.2
3.2
3.1
3 .3
5
4
3
24
24
24
24
45 1
42,6
43 2
41.25
u
Time- minutes to
pickle each sample
-
r·
00
·ia.
-. ·!·
Temerature-
;i·.
;a
X
;i
Area pickled
Total area pickled
172.2
sQ* cm.
,
.i,.
·i
,-·
ri:
Volume of liquor used in p icking
i9,
i··
oi
Volume titrated
25 c c.
1t
3.76
c.c. linO 4
I
=
ln0 4
1 c.c. of
137 o.c.
.00578 grams of Fe
(
II.,I
t1-
1 gram of sample has area of 8.15 sq.
cm.
i
Cost to pickle 1 ton of iron sheets:
/
1.
Cost of iron lost
17 " ac i d
-942
W
i' "Ipower
2.141
r
asi;
r··
·"
;a. i
3'
i
b"·
e··-t?rr
i' "
~,I
Jk
i,
1.az;"
'.,I - .",~6 , z: 2acn
i
15
Follovring are the data taken on the acid pickling of the
second samples (dark blue adhesive scale), sent by the Gen.eral
35$ by weight sul-
Electric Company.
The solution used was
phuric acid and 2
by weight hydrofluoric acid..
Time- minutes to pickle
Area Pickled
13
9
each sample
42
39.7
24
24
sq.cm.
Temperature C0
9
13
39.1
24
24
Total area pickled
SQ. cm.
153.9
Vol-ume of liquor used in pickling
100 c .C
Volume titrated
25 c.c.c
c.c.C iM04
-:
) ,
,
fr7
I,
1 c.c.
IT04
=
.00573 grams of Fe
_-
,3 dd4;;I,
.r
7--
S I_(".',
!
:_
The cost to pickle 2000 lbs. (
ton) of iron sheets by the
straight acid pickling process is as
Iron lost
7i
L_L0
\
1,29
Acid used
p2.44
The saving is:
2 44
2.J4
i-h,3-0
per ton
03,a ~'0
i .
TO STUDY TE
DEPOLARIZING EFECT
ON 'Te
PICLE
OF FERROUS SULP1ATE
LIQUOR.
It has been suggested that the oxygen generated at the
anodes in this electrolytic pickling process might oxidize
the ferrous sulphate to ferric sulphate, and by doing so,
lower the voltage necessary to pickle the iron.
In this part
i
i
1,
.
of the thesis it is proposed to find out if the presence of
I
ferrous sulphate at the anode does lower the voltage necessary
to any appreciable extent.
eans of a porous cup, the
By
anode and cathode portions were kept separate.
was very simple.
[!ii
The theory
All that was necessary to do was to add a
little ferrous sulphate to the anode compartment and
same current
was lowing, that
flowed when there
phate present, read the voltage.
h-,e-a the
was no sul-
As is explained later,
however, difficulties of manipulation made it necessary to
the experiment several times.
.repeat
The cell used consisted of a porcelain cup in which was
placed
a porous cup of the same material.
The cathode
.
liquor
was poured into the outer cup and the ano6e licuor into the
inner cup.
The cathode was a sheet of iron bent so that it
fitted around the porous cup, and the anode was a strip of
lead.
'
The cellwas kept at constant temperature by being immersed
in. a water
bath-.
The first run was made with steam blowing into the outer
compartment in order to keep up the. temperature.; but it was
found that the steam rushing in-churned .
-/-l
liquid so violently
..
I
-I
C-·-------L-
--ur
_
_
~ ~
-
depolarizing effect
Cell used in the study of'the.
of ferrous sphate on the piekl. liquor.
A cathodes of iron
B cathode liquor
C anode;-of iron
D porous cup diaphragm
E anode liquor
F l'iuid in thermostat
G pickling vat
Voltmeter
nd ammeter as shown.
17
.,."
I
I
,thatthe voltage readings were not constant.
The data follows:
Bulphuric acid was in both the outer and inner compartments.
I
II
I
3-05
Amnperes
'
Temp.
In the next rn
2.90
7.2
600
7.2
5OC
200 c.c. of a solution containing 30,
sulphuric acid by weight, and 10% ferrous sulphate, were put
into the anode compartmenrt.
Voltage
2.85
Amperes
7.2
Temp .
j
2.90
7.2
- Temp. of inner
0oC0
cell-the anode
The corresponding acid run was:
Voltage
Amperes
2.85
Z-2
2.83
7-2
0
Temp.
0
.
Next was determined what effect a more concentrated
solution would have.
200 c.c. of 90% sulphuric acid by
weight were used in the anode compartment.
The current was
thought to have some effect, so it was cut down.
The values
found in this run are as follows:
Voltage
Ameres
2.3
2
2.36
2.
Temp
63
63
- Temp. of inner
cell.
I
Then a saturated solution o
ferrous sulphate in 9Q
R
sulphuric acid was made by adding ferrous sulphate while the
temperature was held at 600°C. This solution was poured into
i
the cell.
200 c.c. of the clear solution were used.
The re-
i
sults are as follows:
Voltage
Amperes
Temp. inner cell-anode
"
outer
IT
cathode
2.78
2.5
66o0
68.500
2.76
2 5
66o0
63-.50
-
i
i
Voltage
.
l
out the
Acid was again put into the anode, after ting
anode comoart-ent and washing
used,
(90%) -'
-;ere
200 c.c. acid
it.
with the following results:
Vol tge
2,6
Am-,oeres
2 50
Temp. inner cell
66o0
" oute r
2.6
2 .50
660
68.50C
6s.50 °
"
The voltage here was very 1muchlower than was the voltage on te
first
run with the 90}:acid,
and the oly way to accountfor it
was by su-pos.ing that the electrodes were not in exactly the
run was made. The
irst
were when the
same places as ty
electrodes miht have been closer together, thus forming a
ath for the current, and so the voltage wouldbe less
shorter
than in thefirst run.
ere made
Therefore, another series of runs
electrodes
thle ano
were not moved; the liluid
e com
a rt
ent
In
in
the first r
200 c.c. of
5p
aci3
s
rtllows:
are
2 .58
Voltage
re
iae ers
2.
Tepo. iimner cell
acid
the
out of
bein.g sioned
. The res8ts
w-ereused in the anode comoa.rtmelnt
"
-vhich
outer
bl0
61.25°0
"
For
the next run 200 c.c. o
and
40% ferr--ousslphate
y
a solution of
35>
sulphuric
veight wrerie
uased in the anode
cormpaartment. Res ults as followvs:
Voltage
-Impere
s
Ten-,. inner cell
outer
hissolution
~
2 -49
2.50
tO C
2.45
2.50
61 C
61°z
61.250C
was siohoned out and 200.0.
of
5
acid
ere
i;
19
again put in the cell.
The results are as follows:
Voltage
Amperes
Temp. inner cell
i
"
outer "
2.52
2. 0
61 C
61.25°0
The acid solution was then siphoned out, and 200 c.c. of a
solution, 35% sulphuric acid and 8s ferrous sulphate by:wight,
was put in; with the following result:
I
Voltage
Amperes
2-475
2 .50
Temp. inner cell
610C
"
i
outer "
61.250C
Thisferroussulphate solution was then siphoned out and
200 c.c. of 35% acid solution put in again.
Voltage
Amperes
Results as follows:
2.52
Temo. inner cell
" outer "
2.50
610
61.250C
The results from these last four runs
seem to show that
there is a very slight lowering of the voltage as the content
of the ferrous sulphate is increased. After the first acid
run it was noticed that there was a very heavy deposit of lead
peroxide on the lead anode, which disappeared as soon as the
ferrous sulphate solution was added and current flowed.
This
tended to show that the ferrous sulphate was oxidized to some
extent.
The blue solution of ferrous sulphate also became
yellow as the current continued to pass, showing that ferric
sulphate
was formed.
The drop in voltage which occurred be-
tween the first and second acid run of this
series
could not
be explained by an electric phenomenon, but might be explained
by the fact that the cell had been standing dry for some days
2O
before the run was made, and the solution did not get through
the walls entirely when the first run was made; but after having
made the first acid run and the first sulphate run, the walls
of the inner cell wrere saturated and conducted
the current
better, thus lowering the voltage necessary.
To see if this was a possible explanation, the cell was
left full of acid from Saturday noon until Monday morning, and
then the following set of runs were made. In these runs,the
electrolyte was not removed from the cell, and. the ferrous
sulphate was added directly to the acid in the inner cell.
In
order not to have the volume of the solution in the inner cell
greater when the sulphate was added, every time a given amount
of
errous sulphate was added to the acid in the inner cell a
like amount was added
in volume noted.
to acid
in a graduate, and the increase
Then, when the sulphate was dissolved in the
inner cell, a volume equal to the increase in volume as shown
by the graduate was taken from the cell awith a piopette.
Thus,
the volume in the cell was always the same, the temperature
always the same and, as the electrodes
were always in the same
position,
thecrosssectionexposed to the carrying of the
current was not altered and the only decrease in voltage would
.be due to the.greater conductivity of the electrolyte.
The re-
sults are as follows:
Acid run - 200 c.c. of 35% sulphuric acid (1.21) in inner cell.
Voltage
2.54
Amperes
Temp. inner cell
2.50
590C
"
.i
outer
"
60
="
"·
200 c.c. solution of 35% sulphuric acid and 45/ ferrous sulphate:
Voltage
2.52
Amperes
2. O
Temp. inner cell
"
outer
"
59
O000
200 c.c. solution of 35-~sulphuric acid and
2.52
Voltage
'·
Amperes
2. 0
Temp. inner cell
59 C
n
38 ferrous sulphate:
outer "
6I0T
The last solution was allowed, to run for some time and
ib
i;
became yellow, due to the ferric
finally
toidformed.
This
last set of runs showed that although ferric sulphate was undoubtedly formed, and would increase the value of the by-product,
the depolarizing effect was negligible, and the current saved
would
not amount
to very rmuchwhen it came to figuring the costs
of the plant running expenses.
i.
/
APPENDIX.
ornmulae for Computing the Costs.
(907,200)(cm. per gm.)
(1) Area per ton
(2)
Gin. iron dissolved per sq. cm. =
(33
(4)
pickle liauors)
--- (vol. sampie-or titration) (area pickled).
Total grams of iron dissolved = (area per ton) ( gr . iron
dis. per sq. cm.)
Cost of iron dissolved (total gin.irondis.)(cost per lb.)
(5)
Cost of power to
(c.c.
5nO4)
( iron equiv. per c.c.)(vol.
" o'grams in a poud'C
i9Wi..er
(timneto
ickle
-
ton..
area per
picle)
ton)
---- ·- (c ur
-- · .den. ) (volts) ( cost
of power)
(746)(24)(365) (60
(6)
(7)
Kilos of pure 2SO4
(total kilos iron dssolved)(98
5 5 M. -
Cost of acid =
(kilos of pure
2SO4 )(cost
_ ___
____
(kilos in 1 lb.)(0fH
2 SO4 per
N11
of acid
per 100 lbs.)
_
lb.)
27
A PED IX
Following are the values which ere used in computing the costs
listed in the foregoing pages.
Samples from
iraer. Sheet &
Gcn.eral Electric
Tin Plate Co.
*
t
Saml,)e1
Co.
Sa-mle 2
*
iIht blue* Dark blue
$
>rittie
adhesive
* se,
cle
* scace
&
-
-
Elect.* Acid
Volts- average
1 ec
*2.71
.
-ie I
cid-L '
*
C
*
*
3p.2E
*.
Current Denisity
I
Averae amp/sq .cIm.
*1
*
475*
Time-average min.
*Ove
to pickle
Area
s,
**J10¥0i
Vol. of scamle
for titration c.c.
jI*76
*
06o
2
*
Vol. of sickle
licuors c.c.
!.c.c. of
_1
$
cm.
4
-
*120
ickled
c.c. M O
.069
*
,Ic
0
17 2
*41
*4-
*
$c
25*
10 "
25
*1000
*12
51
*S
460
'
*
2.04
$
l00
*1.65
*
00*
*100
*5-
Ac
J.7b
hi0LO
to
.00573 gramis of iron.
4
4. is equivalent
L
A -
*
24
-- C NC iLU
S ION--
In conclusion, the results of this investigation
can
be summed up as follows:
(1)
While the iron in the ferrous sulphate formed during
electrolytic pickling is undoubtedly
oxidized to ferric sul-
phate and may thus increase the value of the by-product,
is no appreciable lowering of the voltage because of this
(2)
there
reaction.
There is undoubtedly. a saving in the cost of pickling
iron when the electrolytic process is used and. the costs of
materials are as given in the foregoing pages.
The electrolytic
process is very much quicker, thus saving labor eense.
The
product turned out by the electrolytic rocess is better because
cleaner than that turned out by the acid process.
25
-- LIO?:T0GRPEY--
U. S. Patent
;s55,667
U. S. Patent
)iig27,179- July
U.
S.
-
June 4,
1907
1, 1907
$27,180 - July 31, 907
Patent
Clishiam, 0. C.
lv. T. T. Chem. Eng. Thesis
Pastene, R. J.
LF.i.
Rosenthal, C. ii.
LahLrnan, 0.
.
. i.
- InTdus. 1914
. Chem. Eng. Thesis - Indus. 1914
T.
1
Chem. Eng. Te sis
- Indus. 1915
LI. I. T. Electrochem. Thesis -
1916
Storey,
eiet.
& Chem.
Pg '45, 1913
Hering,
Let.
& Chem. Eng.13,
P
Reed.
C.
J.
75,1915
Trans. Amer. Electrochem. Soc.
1-131-1907