232 PEOCEEDINGS OF THE AMERICAN ACADEMY. 



thoroughly washed product was fused with a blowpipe upon a crucible 

 of the purest lime. Electrolytic deposition with silver nitrate as the 

 electrolyte and with a dissolving anode of the pure silver buttons fol- 

 lowed, and the electrolytic crystals were fused in a current of pure 

 hydrogen on a boat of the purest lime. The resulting bars of metal 

 were first cleansed with nitric acid and then were sawed into pieces of 

 a convenient size with a fine jeweller's saw. After the fragments had 

 been etched with nitric acid until free from surface contamination with 

 iron from the saw, they were thoroughly washed with ammonia and 

 pure water, and finally heated to about 300° C. in a vacuum. The 

 silver was preserved in a desiccator over solid potassium hydroxide. 



Pure silver nitrate was prepared by crystallization of the commercial 

 product until free from chloride. That used in analyses 6, 7, 8, and 

 15 was a portion of material purified by Dr. Grinnell Jones for work 

 upon the atomic weight of phosphorus.^ 



In the preparation of reagents the precautions usual in exact work 

 were taken. The ordinary distilled water of the laboratory was twice 

 redistilled, once from alkaline permanganate and once alone, through 

 block tin condensers. Hydrochloric and nitric acids were distilled 

 through quartz condensers, in the case of the hydrochloric acid the 

 first and last runnings being rejected, in the case of the nitric acid two 

 distillations being carried out, the first third being rejected in each 

 distillation. By careful tests it was shown that nitric acid distilled in 

 this way does not contain more than the merest trace of chlorine if the 

 original acid is nearly fi*ee from the latter element. 



Quartz or platinum utensils were employed wherever glass would 

 have introduced objectionable impurities, and electrical heaters were 

 used whenever the products of combustion of illuminating gas were 

 to be avoided. In the crystallization of solids centrifugal drainage was 

 always used to assist in the mechanical removal of mother liquor from 

 crystals, except in the fractional crystallization of the neodymium ma- 

 terial, where it would have been of little assistance. 



The Drying of the Neodymium Chloride. 



The drying of the neodymium chloride for analysis presented several 

 difficulties. Matignon ^ states that if the chloride is first completely 

 dehydrated and then fused in a current of dry hydrochloric acid gas, 

 the product is completely soluble in water. Our earlier experiments 



^ Baxter and Jones, Proc. Amer. Acad., 45, 137 (1909); Jour. Amer. Chem. 

 Soc, 31, 298. 



2 Compt. Rend, 133, 289 (1901). 



