450 PROCEEDINGS OF THE AMERICAN ACADEMY. 



heated for two or three days in the electric oven after all apparent 

 traces of iodine had disappeared. 



This treatment left a salt which gave a perfectly colorless solution 

 when dissolved in a small amount of water. Even the mother liquor 

 that remained after precipitating the chloride with hydrochloric acid 

 gas showed no trace of the yellow color due to platinum or iodine. The 

 salt was precipitated twice successively with hydrochloric acid, each time 

 being washed with a concentrated aqueous solution of the same acid. 

 The analysis of this last sample, as will be seen, was conducted with all 

 known precautions, but yielded, nevertheless, a result 132.877, essentially 

 identical with the last. 



Silver. Since the ratio of silver to caesic chloride was to be deter- 

 mined, as well as the ratio of argentic chloride to caesic chloride, the 

 purity of the silver to be used must be unquestioned. The method of 

 obtaining the pure metal was so nearly similar to that previously used 

 in this Laboratory that further detailing is scarcely necessary. During 

 the electrolytic part of the purification it is well to wrap the anode in a 

 washed filter, as the "anode dust" is then prevented from mingling with 

 and possibly contaminating the pure silver. The sparkling crystals were 

 thoroughly washed, and fused on sugar charcoal, before the blow-pipe, 

 and cooled in a reducing flame. The melted globule was clear, and free 

 from any film ; after cooling it showed no traces of having contained 

 absorbed oxygen. The button was now scrubbed with pure water and 

 clean sand, and cut into small pieces with a clean steel chisel. These 

 pieces were then digested for a short time with dilute nitric acid and 

 washed with ammonia water, in order to remove any traces of iron. To 

 shield them from injurious gases they were kept under distilled water in 

 a small flask. This silver was used in all the analyses, excepting in 

 Nos. 11, 12, 13, 23, 24, and 25. For these analyses the silver was 

 fused in a vacuum on a boat of lime.* 



The hydrochloric and nitric acids used were carefully redistilled, the 

 first and last portions of the distillate being rejected. The nitric acid, 

 of course, showed no trace of opalescence with excess of silver nitrate 

 after suitable dilution, t The phosphoric oxide was resublimed in an 

 oxidizins environment. The water used was redistilled, first with alka- 

 line permanganate, and subsequently with a trace of acid potassic sul- 



* For further information concerning the preparation and purity of silver, see 

 Proc. Am. Acad., 29, 64 (1893); 32. 62 (1896); 33, 121 (1897), etc.; Z. anorg. 

 Chem., 6, 98 (1893) ; 13, 90 (1896) ; 16, 371 (1897). 



t Proc. Am. Acad., 29, 74 (189.3). 



