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Scholars' Mine
Ma0#0 8#0#0 S# R#0#a! & C#a# W0
1927
Te system: calcium oxalate - sulphuric acidJoseph Maple Wilson
F** 0 a aa* 0 a: ://0!*a0+#.+0.#/+a0#0_#0#0Department:
80 8#00 - O# A!!#00 0 % 6 $ $## a # a!!#00 6 # S# R#0#a! & C#a# W0 a S!*a0' M#. I a0 ## a!!##
$ !*0 Ma0#0 8#0#0 6 a a# a+0a $ S!*a0' M#. F +# $+a, *#a0# !a!#a#@+0.#.
R#!++## CaW*0, J0# Ma*#, "8# 060#+: !a*!+ 5a*a# - 0*! a!" (1927).Masters Teses. Pa# 4743.
http://scholarsmine.mst.edu/?utm_source=scholarsmine.mst.edu%2Fmasters_theses%2F4743&utm_medium=PDF&utm_campaign=PDFCoverPageshttp://scholarsmine.mst.edu/masters_theses?utm_source=scholarsmine.mst.edu%2Fmasters_theses%2F4743&utm_medium=PDF&utm_campaign=PDFCoverPageshttp://scholarsmine.mst.edu/student_work?utm_source=scholarsmine.mst.edu%2Fmasters_theses%2F4743&utm_medium=PDF&utm_campaign=PDFCoverPageshttp://scholarsmine.mst.edu/masters_theses?utm_source=scholarsmine.mst.edu%2Fmasters_theses%2F4743&utm_medium=PDF&utm_campaign=PDFCoverPagesmailto:[email protected]:[email protected]://scholarsmine.mst.edu/masters_theses?utm_source=scholarsmine.mst.edu%2Fmasters_theses%2F4743&utm_medium=PDF&utm_campaign=PDFCoverPageshttp://scholarsmine.mst.edu/student_work?utm_source=scholarsmine.mst.edu%2Fmasters_theses%2F4743&utm_medium=PDF&utm_campaign=PDFCoverPageshttp://scholarsmine.mst.edu/masters_theses?utm_source=scholarsmine.mst.edu%2Fmasters_theses%2F4743&utm_medium=PDF&utm_campaign=PDFCoverPageshttp://scholarsmine.mst.edu/?utm_source=scholarsmine.mst.edu%2Fmasters_theses%2F4743&utm_medium=PDF&utm_campaign=PDFCoverPages7/24/2019 The System_ Calcium Oxalate - Sulphuric Acid
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TEE
SYSTEM
CALCIUM
OXALATE
SULPHURIC
ACID
Y
Maple
Wilson r
THESIS
submitted
to
the
faculty of
the
SCHOOL OF MI}mS AND
~ L L U R G Y
OF THE UNIVERSITY OF MISSOURI
in par t i a l fulf i l lment of the
work
required
for
the
Degree
of
MASTER OF
SCIEUCE
IK
CHIITMICAL
ENGINEERING
Rolla Mo
1927
pproved y
J
r:rs;aJ Dl4 J J
Associate Professor
of Chemistry
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T BLE
OF
CONTENT S.
ACknowledgment.
Par t 1.
Introduction _____ 1
Method
of
Conducting the
Investigation
- 2
Preparation of Materials
8
Curves No. 2a
3a
4a Table No. 4a
Curve
l Jo.
1
Table
fo
1
_
~
Curve
No.
2
Table 1: 0.
_
Curve
No.
3,
Table
No.
3
_
Curve
No.
4,
Table
No.
__
-
_
Analytical Methods
11
13-15
16-18
19-21
22-24
25-27
Curves
No.
7-22
Curves 5 6
Tables
5 6
28-29
30-32
Conclusion
33
Bibliography
34
Par t 2.
The Use of
Calcium Oxalate
o n o ~ d r t e
as a Primary
Standard
35
The
Gravimetric Determination
of Calcium
_ _ ~ ~ ~ ~ ~ ~
31
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Acknowledgment
The
author wishes
to take t is means of
expressing
is
sincere
thanks to
Dr
T Schrenk
fo r
suggesting t is
work and
fur ther
fo r h is
in-
tense in t r s t and th e i nvaluab le
aid
given
through
numerous suggest ions and
help
in in terpret ing data
7/24/2019 The System_ Calcium Oxalate - Sulphuric Acid
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Introduction.
The manufacture
of
oxalic acid includes
as one
of the
steps in t he p roce ss t he
conversion
of
calcium oxalate
to the desired oxalic acid by
treatment with sUlphuric acid
and the sUbsequent
cryst l iz t ion of
the
oxalic a cid from
the
solution
of i t
thus made. This
invest igat ion has dealt with
th is
conversion
step
with re ga rd
to
the
various
factors
affect ing
i t The effect
of
time acid
concentration
temperature
volume of solution sol-
ubi l i ty
of
reaction
products and possible compound
formation
have l l been considered
and from
the
information thus gained the conclusion
s been
drawn.
The only reference to any previous work
done along
th i s l ine was that
of Carriere and Vilon
recorded
in Comptes Rendus Vol.
79
1924
page
1402.
However
this
work was conducted
under
some-
what
dif ferent
condit ions
of concentration and ap-
parently
without thought of the application of re-
sul t s
The resul ts obtained in tha t work dif fer con-
siderably
from
the
resul ts of th is
investigation.
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Method of Conducting the Investigation.
To
obtain
the
desired data calculated
amounts
of
sUlphuric acid and
calcium
oxalate
were
git ted
together t a given temperature
un t i l
equi-
l ibrium
was
reached
when a
sample of the
solution
was f i l t e red away
from
the
residue
and
the
amount
of
oxal ic acid formed determined
t i t r t ion
with
a
solut ion
of
KM:n
previously
standardized
against
U
S.
Bureau
of
Standards sodium oxalate. At 25
400 and 55
similar
runs were made maintaining
the tem perature as desi red
in a
thennostat ical ly
controlled water
bath.
The mixtures were agi ta ted
means of a
motor d riven apparatus
constructed
fo r the purpose and
described
in another par t
of
th i s paper.
At
these three
lower temperatures
samples were
taken t
the
temperature of
reaction
f i t t ing the
ot t le c on ta in in g th e
sol id and sol-
ution with a two hole
rubber stopper
through
which
a glass tube bent in
U shape
passed nearly to the
bottom of
the
solut ion. The other end
of
th i s glass
tube was
passed
through a two h ole s to pp er in a
ott le large enough to hold a short funnel and a
receptacle fo r
the
f i l t e red
solut ion and
termin
2
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ated about
3
or
4
em inside the
larger
bot t le
Through
the second hole in
the
smaller bot t le a ir
pressure was applied through a
s t ra ight
glass tUbe
jus t
suff ic ien t to force the l iquid over and
the
pressure
was
allowed to e scape through the second
hole
in
the
stopper
of
the la rger
bott le This
complete arrangement
clamped
in a
stand
could be
lowered into the water
bath
n allowed f i l t ra t ion
a t any temperature
t ha t
could e maintained in the
water
bath The apparatus is i l lus trated by the
draWing
herewith Scrap lead or other heavy material
can be used to
sink
the apparatus
and
to
receive
the
f i l t e red
l iqUid an
8 inch t e s t
tube
was cut to
half
t s
or ig ina l length
The
bo t t l e s
used
to
hold the
reacting
mixture were
glass stoppered 250
ccm capacity
and
were sealed
with
paraf f in to
prevent
dilut ion with
water
The
apparatus
used to
agi ta te the mixture
is best
described
by re fe rr ing to
the
diagrams The
bot t les
a re a ttac he d
by clamps
to
a disc
suspended
j u s t
above
the
water bath
and
this
disc
given
an
osci l la t ing
motion through
a
driving
arm
set off-
center
on
a
small motor driven wheel y
varying
3
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the speed of the motor the speed a t which the ap-
paratus
i s driven
easi ly
regulated.
The sealed bot t les
containing
the
mixture
of acid and oxala te were clamped
in t46 apparatus
and agi ta ted
fo r a length of
t ime suff ic ient
to
allow react ion to
proceed
as
f a r as i t
might
under
the par t i cu la r condit ions of tha t experiment.
The
length
of
ti me n ec es sa ry was determined befo re be-
ginning the inves t igat ion
y
set t ing up a number
of similar samples
and
making determinations
on
them
at various
time in te rva ls from
hour
to
8
hours. At
the
end
of
hour
th e re ac tio n
had ap-
paren t ly reached the same
equilibrium tha t
i t showed
a f t e r
8
hours.
After the
completion of
the 25
40 and
550
runs experiments
were
conducted
to
determine
whether or not the
react ion was
reversible with
a
decrease
in temperature. l
taking samples from
mixtures tha t
h d
been
agi ta ted
a t
temperatures
of
40
and
55
and then
allowed to stand
a t room
temp-
era ture
fo r
severa l days was found
tha t
there
was
pract ica l ly no change in the
amount
of oxalic
acid
present
in
the
solut ion indicat ing
that
the
react ion was not revers ib le with decrease
in
temp-
era ture
6
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After
completion
of the invest igat ion t
these three
lower
temperatures i t was decided to
r ise
the
temperature
to the boi lin g poi nt of
the
solut ion allow
suff ic ient
time fo r
the
reaction
to
take
place
t
th is
temperature and then
take
a sam-
ple of the solut ion f te r
cooling
and determine
the oxalic a c id p re sent
To do
this the calcium
oxalate
with
a
calcula ted
amount
of sulphuric
acid
was put
into
a
Kjeldahl digest ion flask
f i t ted
with
a
thennometer and
a
ref lux condensor
and
main-
tained t ~ boi l ing temperature
for
an hour
In these various invest igat ions not only
the r t io of
sulphuric
acid to
calcium
oxalate
was
var ied
but
also t he concentr ati on
of
acid and
the
to t l volume
of solu t ion
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Preparat ion
of Mater ia ls
Before
s tar t ing
any
of
the
work
i t
was
n ec es sa ry to prepare calcium
oxalate
of suff ic ient
pur i ty
and to
prepare and standardize
solut ions
of sulphuric acid and potassium permanganate
The pure
C204H20
was
prepared y making
a
solut ion
of C.
P
calcium chloride
precipi ta t ing
the i ron and aluminum y
the addi t ion
of
ammonium
hydroxide
and i1 ter ing the a.mHioniacal solut ion
away
from the prec ipi ta ted hydroxides
This sol -
ut ion
was
then allowed
to stand
over night to assure
complete
precip i ta t ion
and
then brought to
boiling
Oxalic acid was added in
small
amounts
allowing
the
solut ion to
come
to
boi l ing
again af te r the ad-
di t ion
of the f i r s t
port ion y
doing
this
and
adding
the acid in small por tions l a rge r c ryst a ls
of
the oxalate are formed
expediting
washing
A fter the addi t ion of
an excess
of
oxalic
acid the
crJs ta l s are allowed to se t t le out and the l iquid
decanted
off The crys ta ls are
then
washed
five or
s ix
times
with
water
containing a l i t t l e ammonia
and
then
washed
with
dis t i l l ed
water
unt i l
a
sample
of the washings
shows
no
t race
of h l o r i ~ s on
t e s t -
ing
with
s il v er n i tr a te
This wil l require an
8
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addi t ional f ive or
s ix
washings meaning a t o t a l
of ten
or
twelve washings of the prec ip i ta te The
c ~ s t l s
o bta in ed a re
drained as d r y a s possible
decanting
off
the
water
and are then
dried
a t
110
0
un t i l
per fec t ly ry They are
then
allowed
to
stand over night
exposed
to the a i r but
protected
from dust
and
fore ign
matter
so tha t any water
of
c rys t a l l i za t ion
tha t might have
been driven off
can
be
regained
The
sa l t
th us p re pa re d
i s kep t
in
glass stoppered bot t les unt i l needed
I t is
of
very
high pur i ty as shown the resul t s of analyses
of
three dif ferent ba tches g iven herewith:
Percent
CaC204H20 in
sam.ple
Sple
Sple 2
Sple
3
Sple
4
Batch
99 46
99 55
99 50
99 46
Batch
99 95
99 95
99 99
99 95
Batch
3
99 94
100 09
99 96
99 75
Approximately 4N
sUlphuric acid was
pre
pared tak ing acid of ap. gr
1 84
96
H
S0
4
and
di lu t ing w ith the
calculated
~ u t of water
This
solut ion
was
then standardized
weighing out
a
sample
of
previously ign i te4 sodium carbonate
and t i t r a t ing with
the
acid
- 9 -
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The
solut ion of potassium per manganate
used was taken
from
a previously p re pa re d s to ck
solut ion which had been made up approximately O IN
agi ta ted blowing a i r through i t fo r severa l hours
and then
allowed
to
stand fo r not
l e ss
than 3 days
The
solut ion thus prepared fa i r ly stable and
does
not change
in
s t rength appreciably
in as
long
a
per iod
as 3 months
i f
kept
stoppered
and away
from strong l i gh t t was standardized
against
a
s ~ n p l of
Bureau
of
Standards s o i ~ ~
oxalate and
res tandardized from t ime to time to keep check on
a poss ib le
change
in t oxidizing power
10
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Analyt ical Methods.
All
n ly t ic l
methods used
whether
fo r
actual
analysis
or fo r
standardizat ion were the
o ~ m o n standard
methods.
determine oxal ic
acid in s ~ n p l e s of
the
sOlutions a 5 cern
sronple of
the
solut ion
was
used di luted
to
approxinately
75 ccm.
an excess
of sulphuric
acid
added and th e so lu tio n t i t r ted
hot
with
the
standard
permanganate.
considering
this 5 ccm
sample as an al iquot of the to t l sol -
ut ion the ~ n o u n t
of
permanganate necessarJ for the
whole sam ple could be calculated and th e p erc en t
of
conversion of calcium oxalate
to
o xa lic a cid
could be f igured .
In analysis
of
the
calcium oxalate
to
de-
termine i t s
pur i ty the
weighed sample of s l t was
dissolved
in
1 10 sulphuric
acid heated
almost
to
boi l ing
and t i t r t ed hot with the
permanganate.
As has
been
sta ted the permanganate was
standardized
against Bureau of
Standards s o i ~ ~ ox-
l te qy weighing
out a s ~ i p l of
the s l t dissolv-
ing in 1 10 S Ulp hu ric acid
heating almost to
boi l ing and t i t r t ing
hot.
standardize the SUlphuric acid Na2C03
11
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was
prepared ignit ing
pure NaHC 3
to dul l
red
heat fo r
1 hour A
sample of
the sodium
carbonate
thus made was weighed out and dissolved in is-
t i l l e water and
t i t r t e
with
the sUlphuric acid
using
metbwl
orange as the indicator
12
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Curve N o 1 Table o 1
This
curve
plot ted
from
data
in
the ac-
companying table shows
the
conversion
of calcium
ox ala te to oxalic
acid
a t
25 with
concentration
of s ul phuric a ci d constant
and
volume of solut ion
varied.
The
experiment
was
s tar ted with 100 per-
cent
excess of
the amount of
acid necessary to
re-
ac t
with
the amount of oxalate used.
The
acid
was
a l l
cases
4.450N and
the
amount
used
was
varied
as shown.
Conversion
to
o xalic a cid varied from
45.83
a t 100
excess acid to 95.8
at 500
excess
acid .
Between 4
conversion and
5
conversion
there
i s apparently
a break
in
the
curve and
the
second
invest igat ion a t
the
s ~ temperature shows
th i s
break
more
clear ly defined.
Also as
in
a ll
the
other
cases
i t
may be noted that
as the con-
version nears
100
there s
a marked decrease
in
the gain of o xalic a cid over each preceding point .
In th i s case and in those
following
two
independent determinations were
made
in
order
to check
the resu l t s
-
13
-
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T LE
:ro
See
Curve Uo.l
Showing
conversion
of a l c i ~
Oxal-
a te to
Oxalic
acid a t
25
0
C Volume of
sol
ution
equal
to
volume of
4.450N H2S04
used.
Percent
H SO
Percent
Con
used in
excess
version
of theore t ica l
A
B
100
45.83
45.83
110
49.20
49.35
140
51.68
51.72
160
53.25
53.65
180
55.28
55.40
260
68.60
68.75
300
77.05
77.05
340
83.86
84.08
380
89.6
90.2
420
94.6
94.7
460
95 5
95.5
500
95.8
95.8
Note:
Columns
A
and
are
duplicate
samples fo r checking.
14
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7/24/2019 The System_ Calcium Oxalate - Sulphuric Acid
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Curve N o 2 Table
No. 2
This
curve, plot ted from data in the ac-
companying table
shows
the
conversion
of calcium
oxalate to oxal ic acid a t 25, with the
volume
of
solut ion
constant,
and concentration
of
sulphuric
acid
varied.
The
experiment
was
star ted with the
theoret ica l
amount of sulphuric acid nec es sar y to
react
with
a
given weight of
calcium
oxalate,
and
then th i s ~ o u t increased
as
shown.
The
acid used
was 4.450N,
and the ~ u t
used was
di luted to
100
cern. The conversion varied
from
5.64
with
the
theoret ica l
amount of acid to 95.9 with 540 above
theoret ical
There
i s a regular increase
in
the
amount of oxal ic acid formed
up
to about 32 con-
version,
when
the amount of
decomposition of
the
oxala te
increases very
rapidly
up to about 54
a f t e r
which
increases
a t a
less rapid
rate, and
regularly, up
to
the
maximum.
As in
the
preceding case,
two
wholly
in -
dependent
samples were
run, and these
are both shown
in
the
table and on
the curve.
16
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T BLE NO 2
See
Curve
No 2
Showing convers ion of Calcium Oxal
ate to
Oxalic acid a t 25 C Volume of
sol-
u t i on equa l to
volume of
4.450N
H2S04 used
d i lu t ed
to 100 cem
e r e ~ t H
2
SO
4
Percent Con-
used
In excess version.
of
theoret ical
0
5.64
5 64
20
6.54
6 62
60
9 88
10.28
100
11 53
11.53
4
14 94
14 98
180
18.80
20.52
220
20.99
22.25
260
25.80
26.42
300
31.38
31.50
340
53.31
56.81
380
61.05
62.50
420
67 35
69.40
460
78.80
79.60
500
84 25
84.50
5
94.70
95.90
17
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Table
N o 3
Curve No. 3
This curve
and
i t s
accompanying
table
show the conversion
of
calcium oxalate to
oxalic
acid
a t
40. The volume of s olu tio n in th i s case
was
constant with
the concentration
of
sulphuric
a cid v arie d. The acid used
was
4.450N and was
used in
varying amounts as in dic ate d. In each case
the
amount of
acid used
was diluted
to
a
volume of
100
ccm. Start ing
w ith the
theoret ical
amount
of
sulphur ic
acid
to reac t with a given weight of the
oxalate the
percent conversion to
ox alic acid varied
from 7.04
a t
theore t ica l
to 97.3 with 540 excess
sulphur ic
ac id The
increase
in the
amount
of de-
composition
i s very regular
up
to about 90 where
the
fonnation
of o xalic a cid increases less rapidly
from tha t point to the
maximum.
As
before two
independent
samples were
run so tha t resu l t s might be
checked.
- 19 -
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TABLE NO
See Curve
No.3
Showing conver sion o f Calcium Oxal-
ate to
Oxalic acid
a t 40 C o l ~ ~ of 501
ution equal
to
volume
of
4 450N
H
2
S04 used_
; diluted to
100
ccm
Percent H SO
Percent
Con
used
in excess
version
of
theore t ica l
A
B
0
7 04
7 08
20
8 40
8 40
60
13 10
13 13
100
14 50
14 60
140
19 18
19 38
180
25 40
25 40
220
30 60
30 60
260
37 52
37 52
300
42 82
44 38
340
53 2
53 2
380
63 68
64 19
420
73 48
73 48
460
90 76
92 35
500
95.5
95 5
540
97 1
97.3
20
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Table N o 4 Curve No. 4
This
shows
the
conversion
of calcium
ox-
ala te to oxal ic acid a t 55 w ith the volillne of sol-
ut ion constant
and
concentrat ion
of
acid
varied .
The
acid
used
was 3.822N and
the
araount
of th is
acid
to reac t theore t ica l ly with a cer ta in
weight
of calcium oxalate was
calculated
The acid was
then
used in varying ~ o u n t s as shown and
~
each
case
the
volume
of acid was di lu ted to 100 cern. The con-
version
to oxal ic
acid varied
from
8.55
w ith the
ore t i ca l
s ul phu ri c a c id to
96.58 with 540 excess
acid .
in the
other cases the
increase
is very
regular
u n t i l
the
percent
decomposition of
the
ox-
ala te nears the maximum, when an increase in the
amount of
sulphuric
acid causes a l e sse r increase
in the
oxal ic
acid
produced than fo r preceding
points .
In t h i s and curves
2
and
3
wil l
be noted
tha t
a l l are
of
the
same genera l shape the only
dif ference
being the marked
break
occuring
in curve
2 and t ha t each
curve i s a l i t t l e
to the r ight of
the one a t the next lower temperature and
has
a
s li gh tl y g re a te r
slope than the
preceding
one
up
to
between 80 and 90
decomposition. This
temperature
effec t i s bes t shown in curves
7-22.
-
22
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T BLE NO 4
See Curve
No 4
Showing convers ion of
Calcium Oxal
ate to
Oxalic
ac i d
a t 55
C
Volume
of
sol-
ut ion equal
to
volume of 3.822N
H2S04 used
diluted to 100 ccm.
Pe rcen t
H2SO4
Percen t Con-
used
in excess
vers ion
of
t h eo r e t i c a l
0
8 55
8.96
20
9 83
9.90
60
13.39
14 1
100
19.00
19.17
140
25.78
25.84
180
31.26
31.30
220
38.47
42.42
260
51.58
52.17
300
58.15
59.67
340
69.15
69.50
380
80.40
80.49
420
81.75
93.13
46
94.18
95.78
500
91.87
96.12
54
~ 8 7
96.58
23
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Table
No. 4a
Curves
No.
2a 3a
4a
These
curves
and
the
accompanying
table
are merely the data
of t les no 2
3
and 4 and
t h e i r
curves assembled
fo r ease of comparison
They
d i f fe r only
in
th t ea ch valu e
in the
table
and the
corresponding points
on the curve are
the
mean
of tlle two v alu es giv en in
columns A
and
B
in
the preceding
tables
and
hence are
the mean
of
the
two seperate and independent
runs
25
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TABLE
TO
4a
See Curves No 2a ,
3a,
4a
Showing conversion of Calcium Oxal
ate to
Oxalic
acid
a t
25,
40, and 55
C
Volume of solut ion constant, acid.
concentra-
t ion varied. Each value i s mean of two in-
depenAent1y
determined
values.
H2S04
in
excess of
the
ore
t i c a l
o
20
60
100
140
180
220
260
300
34
8
4
460
500
54
Conver
sion
a t
25
0
1 8
11.53
14.95
19.71
21.64
26 .05
31 44
55.06
61 81
68.43
79.19
84.47
95.38
Conver
sion
a t
40
7.06
8.40
13 12
14 .55
18.83
25.33
30 .61
36.66
44.30
53.20
63 73
73.33
91 33
95.18
97 .09
26
Conver
sion
at
55
8.76
9.87
13.75
19.08
25.81
31.28
40.45
51.87
58.91
69 32
80 .44
87 .44
94.98
93.99
96.22
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Curves 7 22
These curves were
plot ted
from
the
d t
of
t le
4a and
show
the
inc re se of ox l ic
cid
formed with the
i nc re se
of
t empera ture .
Each
curve
represents
cer t in
c id concentration as
indicated with constant volume of solut ion and
varying temperature.
wil l be noted
th t
three poin t s have
been
in terpolated
from
other
curves in order to
complete the
curve
t 2
excess
sulphur ic i d ~
28
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Curves
5
6 Tables 5
6
These
curves
plot ted
from
data
in tables
5 and
6 show
the
~ r n t o x lic c id formed the
act ion
of
sulphuric
acid
on
calcium
oxalate at the
boiling po in t of the di lu te acid solution used
Which
i s approximately 1000. The
VOlume of
solution
was kept constant and t he concent ra tion of acid
used varied
as
indicated.
Curve n ~ 5 shows
the conversion
in 100
cam. volume and curve no. 6 shows the same for
cern.
volume.
Both of these curves
are
very regular
the amount of oxalic acid increasing with the acid
concentration
and
increasing more rapidly
t
higher
acid concen trat ion. t
might
be
noted also
that the
two
curves cross t
about 27.5 conversion
but both
retain the i r regular shape
throughout.
In the case of
curve
5
the amount
of acid
calculated was th t
to
r e c t
theoretical ly with
3.7631 groa. of
calcium oxalate .
For
curve
no . 6
the weight of
oxalate used
was
3.6197
gms.
30
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TABLE NO 5
See Curve
No 5
Showing
conve rs ion o f
Calcium
Oxal-
ate
to
Oxalic acid
a t
B P. of solution, Ap-
proximately 100
0
C
Volume
constant
a t
100 cem.
Percen t
H2S04
used
in
excess
of theoret ical
o
100
200
300
T BLE NO 6
See
Curve No 6
Percnet
conversion
to H2C2 4
10.5
22
Showing
conversion
of
Calcium
Oxal-
a te to Oxalic
acid a t B P. of solution,
ap-
proximately 100
0
C. .
Volume
constant
a t
5
Gem
Percent
H
2
S0
4
used in
excess
of t heo re t i ca l
o
100
200
300
31
Percent
conversion
to
H2C204
8.90
21.3
61.4
98.97
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Conclusion
I n c on clu sio n th e
fol lowing
f ac t s
are
noted:
1
The
convers ion
of
calcium
oxala te to
oxa l ic
ac id increases with an
inc rease in the
temp-
e ra tu re a t
which
reac t ion
ta ke s p la ce regardless
of the c o n c e n ~ r a t i o n
of
sUlphuric acid
used
2
The
conversion a l so
increases
with
an
increase
in the
wnount
of sUlphur ic
acid
used
re -
gardless of t emperature
3 Th e
conversion
of
calcium
oxalate to
oxa l ic
acid
with
sUlphuric
ac id
does not
fol low
the
s o ~ u b i l i t y of calcium sulphate
and
i s apparen t ly
very littl dependent on it
4 As
ga the red
from th i s inves t iga t ion
the bes t condi t ions fo r the conversion of c a l ~ i u m
o xala te to oxa lic ac id are
those proven
in curve 6
namely
the
fo l lowing:
T ~ p e r a t u r e
b oi l in g p oin t of so lu t ion
Time: 45 minutes to
1
hour
Acid
concentra t ion: approximately
4N.
Amount ac id : 300
in excess of
the
amount fo r t h eo re t i ca l
reac t ion
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Bi bliograpby
t Etude
experimental
de
actio n
de
acide
s u l f u r -
i q u e
s u r oxa l a t e de
calcium.
It
E.
C arri ere
E
Vilon.
omptes
Rendus
des
Seances
de
l Academie des Sciences.
Vol. 179
1924
page 1402.
4
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The
Use
of
Calcium Oxalate
Monohydrate as
a r ~ r y Standard fo r Volumetric
Standardizations_
The comparat ive ease
with
which the calcium
oxalate monohydrate could be prepared and i t s high
degree of pur i ty and
constant
analysis gave r i se to
the possib i l i ty of i t s
use
as
a
primary standard in
volumetric
quanti tat ive
work The invest igat ion
was
not completed but
some
data was taken which
shows
the poss ib i l i t i es
To
get
th i s
information a solution of
KMn
was standardized
on
Bureau of standards
Na2C204
and then
on some of
the
CaC
2
0
4
H
2
0 p rep ared a s on
page
8
of
th i s
paper The resul ts
were
as
follows:
N orm ality o f
KMn by :B of
S
Na
2
C
2
0
4
0 1060
1060
1062
1062
Normali
of
KMn
by
CaC204 H20
0 1063
1063
1064
1064
This
comparison
shows
tha t
there
i s a
con-
s tan t
nonmality
v alu e o bta in ed
by
the
use
of
the
cal-
cium sa l t
which does not d i f fe r more
than 4 in the
four th
s ign i f i can t
f igure from the value obtained by
35
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the
use of
sodium
oxalate
t i s the belief of the
author
that
further
invest igat ion wil l prove
the value
of CaC2 4H2
as
a
primary
standard
6
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The Gravimetric Determination of Calcium
as
a
2
0
4
.H
2
The
high degree
of puri ty
evidenced
by the
analyses
of the calcium oxalate prepared as in Part 1
of th is paper
and the constant values of the weights
of
samples
of the sa l t
lead
to the bel ief tha t i t
might pos s ib ly afford the
means
of a simpler gravi
metr ic
method
fo r t he det erminat ion of calcium
than
tha t
now in
use
namely
precip i ta t ing
as
the
oxalate
drying and weighing direct ly
as
CaC204H20 instead
of igni t ing a nd w eig hin g as CaO
Consequently
in -
vest igat ion
was
s ta r ted
along th i s l ine.
A solut ion of
P. calcium chloride
was
prepared and standardized and from this samples of
oxalate were
precip i ta ted
and weighed . The
calcium
oxalate was
precip i ta ted
by
the addi t ion
of
oxalic
acid
to
an ammoniacal solution of
the
calcium chlor-
ide and was then f i l t e red on a Gooch crucible
washed
with water containing a l i t t l e ammonia f inal ly
with
dis t i l l ed
water and then dried
f or d if fe re nt
lengths
of time and
a t
dif ferent
temperatures
as
shown
in the
following
tab les
7
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TABLES.
Showing resu l t s of attempts to determine
Ca by weighing
a s
cac
2
0
4
-H
2
0.
af ter
precipitat ing
from a
solut ion CaC1
2
0.1167 N.
Theoretical weight
Weight
a f t e r
:ercent
CaC
2
0
4
-H
0 in
drying
a t
110
0
error
sample
of
sol n.
fo r 25
hours
_
0.2130
0.2178
/2.25
.2130
.2181
12 39
.2130 .21?6 /2.16
.2130
l?4
12 06
These same samples were
then
dried for
an
addit ional 4 hours a t 140
0
with th es e
results :
Weight af ter Percent
4 hours a t
140
0
error
0.2096
-1.59
.2119 -0.52
.2106
-1.13
.2098
-1.50
After
th is treatment
the
samples
seemed to
gain weight
slowly
while
weighing,
and accordingly
they were
allowed
to stand in a ir for
a
number of
hours
and weighed at in tervals to determine
the
change
in weight_
The resu l ts are
shown in the following
-
38
-
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table:
Weight
a f t e r
standing in
a i r 4
hours
0.2145
.2155
.2147
.2142
Weight
a f t e r
sta.nding in
a i r 14
hours
0.2178
.2182
.2176
.2174
Weight
a.fter
standing in
a i r 50 hours
0.2166
.2168
_2162
.2160
This
invest igat ion
shows
~
the
deter
mination of calcium as
CaC2 4 H2 i s
not accurate
enough f or quan ti ta ti ve work.
t
would be necessary
to regulate
both
time and temperature
too del icately
to permit
th is
method
to
become
pract icable .
he
calciuIn
oxalate
s precipi ta ted appar
en tly lo se s
some of
i t s water of crystal izat ion
which
i t
regains
on
exposure
to
a i r