The System_ Calcium Oxalate - Sulphuric Acid

7/24/2019 The System_ Calcium Oxalate - Sulphuric Acid

1/43

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.
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2/43

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


3/43

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


4/43

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


5/43

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.


6/43

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


7/43

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


8/43


9/43


10/43

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


11/43

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


12/43

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


13/43

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 -


14/43

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


15/43

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


16/43

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


17/43

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

-


18/43

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


19/43


20/43

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


21/43

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


22/43


23/43

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 -


24/43

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


25/43


26/43

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

-


27/43

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


28/43


29/43

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


30/43

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


31/43


32/43

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


33/43


34/43

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


35/43

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


36/43


37/43

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

33


38/43

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


39/43

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


40/43

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


41/43

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


42/43

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

-


43/43

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

Documents

The System_ Calcium Oxalate - Sulphuric Acid