ww 
Si 
LS) 
First analysis: Percent Ag in AgNO; cale. 63.50, found 65.24. No. 
of washings, 8. 
The crucible was then washed thoroughly with pure water until all 
apparent traces of AgCl had been removed, dried at 140° and again weighed. 
Gain in weight, .0162 gr. 
Second analysis: Percent Ag calc. 63.50, found 64.04. The crucible 
was now thoroughly washed by suction with NH,OH to remove all AgCl and 
water to remove all NaCl from the pores. Weighing gave the original value 
for the crucible. 
Pure dilute HCl was substituted for NaCl so that the error might not 
be due to the precipitating agent. 
First analysis: Percent Ag calc. 63.50, found 63.52. 
Second analysis found 63.60. 
Finally a solution of purified KCl, a slightly more soluble salt than 
NaCl was tried. The empty crucible was in all cases washed with NH,OH 
and water and it varied in weight by only one-tenth milligram. 
Percent Ag cale. 63.50, found 63.98. 
In all the analyses the AgCl precipitate was easily handled, the diff- 
culty arising in the seeming impossibility of washing out of it and the pores 
of the crucible the NaCl and the KCl. 
II. Determination of Cu in CuSO,4.5H.O as CuSCN. 
This analysis seemed particularly adaptable because of the extensive 
use of the Gooch crucible necessitated in it. A solution of crystals of very 
pure CuSO;.5H.O was made such that each 50 ¢. ¢. contained .2136 grams. 
Precipitation of CuSCN was affected from the hot solution. in the presence 
of an excess of H.SO; by means of (NH,4).SCN. Drying was at 140°. 
Percent Cu in CuSO, cale. 25.46 found (1) 26.80 (Stirred 2 minutes and 
~ not permitted to 
settle.) 
(2) 25.24 (Stirred 4 minutes rap- 
idly and digested 15 
minutes. ) 
(3) and (4) 25.39 (Stirred 4 min- 
utes rapidly and digested 30 
minutes. ) 
By thoroughly washing with water, drawn both ways through by suc- 
tion and drying at 140°, the crucible maintained a weight varying only by 
