352 



First analysis: Percent Ag in AgX0 3 calc. 63.50, found 65.24. Xo. 

 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 XH 4 OH to remove all AgCl and 

 water to remove all XaCl from the pores. Weighing gave the original value 

 for the crucible. 



Pure dilute HC1 was substituted for XaCl 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 KC1, a slightly more soluble salt than 

 XaCl was tried. The empty crucible was in all cases washed with XH 4 OH 

 and water and it varied in weight by only one-tenth milligram. 



Percent Ag calc. 63.50, found 63.98. 



In all the analyses the AgCl precipitate was easih' handled, the diffi- 

 culty arising in the seeming impossibility of washing out of it and the pores 

 of the crucible the XaCl and the KC1. 

 IT. Determination of Cu in CuS0 4 .5H 2 as CuSCX. 



This analysis seemed particularly adaptable because of the extensive 

 use of the Gooch crucible necessitated in it. A solution of crystals of very 

 pure C11SO4.5H2O was made such that each 50 c. c. contained .2136 grams. 

 Precipitation of CuSCX was affected from the hot solution in the presence 

 of an excess of H 2 S0 3 by means of (XH 4 ) 2 SCX. Drying was at 140°. 



Percent Cu in CuS0 4 calc. 25.46 found (1) 26.80 (Stirred 2 minutes and 



n t permitted t o 

 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 



