14 



The great difference in the rap dity of decomposition of different 

 samples of oxide made it desirable to study the influence of the 

 method of preparation of the oxide upon its decomposition. It 

 seemed prol^able that the difference between samples was either due 

 to varying quantities of impurities or to variations in the physical 

 state; for example, in the fineness of division of the powder. Pure 

 silver oxide was therefore prepared for study in three different 

 wa3's. For all these preparations silver nitrate purified by several 

 recry stall zations was used. In the first case sodium carl>onate was 

 added. The precipitated carlionate was washed repeatedly by 

 decantation, the last washings occupying twenty -four hours each. 

 It was then dried and heated at 240° for twenty-four hours to drive 

 of¥ as completely as possible the water and the carbon dioxide. The 

 second and third preparations were made by treating the silver 

 nitrate with a clear solution of barium hydroxide, in one case with 

 both solutions at room temperature, in the other with Ijoth at 100°. 

 All the solutions were very dilute and the reaction was carried on 

 Avith the exclusion of carbon dioxide. The precipitates were 

 carefully washed, and dried at 240°. 



It was ex})ected that the silver carbonate would yield a very 

 finely divided oxide and, therefore, one that would rapidly de- 

 compose, but as a matter of fact it proved to react much more 

 slowly than any which had previously been tried. The samples 

 prepared with barium hydroxide decomposed more slowly still — 

 more than four times as sloAvly as the oxide used in the earlier 

 experiments. Contrary to expectation the oxide prepared in the 

 cold decomposed rather more slowly than the other. 



Therefore, it would appear from these few experiments that the 

 rapid reaction of some of the samples was caused by the presence 

 of impurities. Still, my experiments were hardly sufficient to 

 make this conclusion certain, especially as certain observations 

 led me to suspect that the rapidity and temperature of drying 

 had some influence on the rate of decomposition. Unfortunately, 

 however, my experiments at this point had to be brought to an 

 abrupt close, and it is therefore necessary to leave this question 

 open. 



