The Students' Guide in Quantitative Analysis - Free Ebooks Library

ILORIDE OF LIME.
Valuation of Chloride of Lime.
Penot's MetlmL From Frc.eniiis' Qmnt. Analysis,
s .00 Based oa the conversion of an alkahnc arsen.t^'.
into an arseniate by a solution of chloride of lime.
As,0, + CaCUO, = As.Gs + CaCU.
The end reaction is determined by KI and starch, undecom
posed hypochlorite turning this mixture blue.
(, )
Prcpamtiou of Kl Starch P«/.t.-Bo.1 three grms.
^tich n. 250 c.c. water, add one grm. KI, one grm.
fj.^^COj + aq. ; ddute to 500 c.c. Moisten paper with
this solution and dry.
- ib) Prcpamtim of Solution of ..L-.t}^. - Dissolve ex
actly 4,9s grms. pure sublimed As.O, wah 25 grms
Nai03 +-^aq. (free from S) in 200 c.c. water. ^Bod until
Jissolved and dilute to one Utre. Make a j; s^l^^'""'
Since it is difficult to weigh out exactly this amount, take
any number and dilate proportionately. If 5.0^3 g^"^^-
then
4.95 : 1000=
5 -Of 3 grms. :
10127.
Add then 12.7 c.c, to the litre. One c.c. of this solu-
tion — 0.00355 CI.
(c) Process of the Determination. -^l\^ sample well;
weigh out 10 grms., rub in mortar with 50 or 60 c.c. water
settle; decant turbid liquid into a litre flask. Repeat.
Fill up ro mark, and mix.
Fill a burette, take 50 c.c, run it into a beaker, add the
standard As,03 solution, stirring until a drop of the so-
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