The Students' Guide in Quantitative Analysis - Free Ebooks Library

CALCULATION OF ANALYSIS. ,
^
keep warm while the precipitate settles. Test with a
dropof H^SO,; wash with boiliitg water by decantation ;
then bring the precipitate on a No. 2 filter wash well dry
; ;
and ignite precipitate in a platinum crucible burn filter m
;
a cradle as above, and add ashes to contents of crucible.
Sec Frcs., § 7 1 . '?•
jVi,/tf._Wash until the filtrate gives no precipitate with
A*NO When estimating barium in the presence of
nitrates, chlorides, etc., these salts arc sometimes carried
down with the BaSO^. Since it is impossible to remove
these by washing with water alone, treat the precipitate
with very dilute HCl. or ammonie acetate. Cf. Crookes'
Selea Methods, page 312.
C. Determination of Watw (by Ignition)—
In a weighed crucible weigh out i to 1.5 grms. substance;
heat very gently at first over a small flame, and increase
the temperature very gradually ; finally, heat to low redness
then cool, weigh, and repeat the operation until the weight
remains constant. Caution
else the CI will be expelled.
t
15
: avoid too liigh a temperature,
When substances contain large
percentages of water, as magnesic sulphate, hydrodisodic
phosphate, alum, etc., begin to expel the water at ioo- C.
in an air-ba.th.
D. Calculation of Analysis-—
See Fresenius. page 79S, ^ilao § 196- Make two state
ments, the first to determine the amount of the desired
constituent in the precipitate obtained:
Actual |
, 1 At. Wt. of the 1 Actual
\
Mol.WUof I . constituent = \ weight of [ : weight of \
precipitate f desired precipitate constituent.
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