in Gravimetric Analysis. 



457 



all by the current, and there is a tendency for traces of the 

 silver to remain behind in the crucible. The current density 

 employed was about '0012 ampere per square centimeter of 

 cathode surface and the time about twelve hours. After 

 weighing the silver deposited, it was dissolved in nitric acid, 

 precipitated by hydrochloric acid and weighed again as the 

 chloride, giving a check upon the results. 



Seven of the ten determinations of Table III were thus 

 treated, but owing to the imperfections of the process the 

 results were all slightly low, the worst showing a deficiency of 

 •0025 grin, of silver, an error of less than 0*9 per cent. The results 

 of the two best of these determinations given below are, how- 

 ever, sufficient to prove the point in question, namely that the 

 silver sulphocyanide dried at 115° has the theoretical constitu- 

 tion and contains no water. The numbers are those under 

 which the determinations appear in Table III. 



taken Ag. 



grm. grm. 



4. -4375 -2844 



JO. '4369 -2840 



!ound by 

 battery. 



Error. 



Weighed 

 as AgCl. 



Calc. as 

 Ag. 



Error. 



grm. 



grm. 



grm. 



grm. 



- grm. 



•2839 



— 0-0005 



•3765 



•2834 



—o-ooio 



•2S38 



— 0-0002 



•3761 



•2831 



— 0-0009 



It is clear therefore that the estimation of sulphocyanides by 

 precipitation with silver nitrate and direct weighing of the 

 precipitate is wholly permissible. The method is extremely 

 simple and, as has been shown, the results are quite accurate. 



In conclusion I wish to thank Prof. F. A. Gooch for many 

 valuable suggestions given daring the course of this inves- 

 tigation. 



