178 



PROCEEDINGS OF THE AMERICAN ACADEMY. 



vigorously shaken. After a day or two the mixture was filtered 

 througli a weighed Gooch crucible and the precipitate was shaken and 

 allowed to stand with many successive portions of water containing 

 five milligrams of argentic nitrate to the litre. It was finally trans- 

 ferred quantitatively to the crucible, washed with pure water to 

 remove the traces of argentic nitrate and dried at 160° in a porcelain 

 drying oven in a stream of air purified by ()assing over sulphuric acid 

 and potash. The two litres of filtrate were allowed to stand until the 

 shreds of asbestos had settled ; and these were collected upon three 

 thicknesses of the best filter paper, ignited and weighed. The main 

 body of the precipitate was transferred to a porcelain crucible, weighed, 

 fused in a porcelain oven, and weighed again. Below are the data. 



Goocli crucible alone . 

 Gooch crucible + AgBr 



Argentic bromide in air 

 Correction to vacuum . 



Chief mass of argentic bromide in vacuum 



Porcelain crucible + AgBr 



The same after fusion 



Loss on fusion .... 

 Crucible + ash + asbestos 

 Crucible 



Ash + asbestos . 

 Ash of three filters 



Asbestos 



Total weight of AgBr 



Subtract amount corresponding to } 



1.42 + 0.20 = 1.62 c.c. HBr solution . . | 



Argentic bromide corresponding to z 

 bromide 



incic ) 



Common 

 Weights. 



Grams. 

 18.4812 

 27.2633 



25.0757 

 25.6755 



15.2857 

 15.2853 



Standard 

 Weights by 

 Substitution. 



Grams. 

 0.22840 

 y.01052 



.37781 

 .37700 



0.00021 

 0.05284 

 0.05226 



0.00058 

 0.00012 



0.00046 



Standard 

 "Weights 

 corrected. 



Grams. 

 0.22840 

 9.01050 



8.78210 

 0.00039 



8.78249 



0.00021 



0.00046 



8.78274 

 0.00282 



8.77992 



Thus 5.2G449 grams of zincic bromide correspond to 5.0436 grams 

 of silver and 8.77992 grams of argentic bromide. If bromine and 

 silver are taken as 79.955 and 107.93 as usual, the atomic weights 

 of zinc computed from" these ratios are identical, — 65.404. Since 

 this is the case, of coui-se the per cent of silver found in argentic bro- 

 mide Itojo X 100 is identical with that obtained by Stas, or 57.445. 



