THE FUSION OF ARGENTIC SULPHATE. 

 The Loss of Weight Caused by Slight Decomposition. 



The loss in weight was thus on the average only 0.08 mg. or 0.0015 per 

 cent. In seems certain that at least part of this loss in weight was due to 

 a deficiency of either oxygen or sulphur trioxide in the darkened sulphate, 

 and not to the loss of an illegitimate excess of the latter substance. There- 

 fore, although it may be a debatable question as to whether it is safer to 

 take the weight of the white or darkened samples as the true weight, it 

 seems probable that the weight of the white sample was more trustworthy. 

 Even at the worst the uncertainty can not have been greater than 0.001 

 per cent. This result agrees with the earlier conclusions already cited con- 

 cerning the obvious effect of very slight decomposition on the color of sil- 

 ver salts. It appears that in the present case, as in the others, the slight 

 stability of these compounds is a real assistance in the production of a 

 typical compound, instead of a hindrance to precise quantitative work. 



For weighing the argentic sulphate, and of course the chloride also, 

 the Troemner balance which had served in many similar researches was 

 used. 1 The Sartorius platinized brass weights were standardized by the 

 usual Harvard method. 2 



As usual, all weighings were made by substitution, a make-weight being 

 placed on the right-hand balance pan. In order to avoid as far as possible 

 any error due to changing meteorological conditions, a substituting coun- 

 terpoise of the same material and approximately the same surface and 

 weight was used. Every weighing was repeated, and the successive values 

 seldom differed more than 0.03 mg. No difficulty was experienced from 

 hygroscopic adsorption of water by either argentic sulphate or argentic 

 chloride, except on a few days when the air was unusually humid. In these 

 cases the tube was heated to about 330 and allowed to remain in a desic- 

 cator until the conditions were more favorable. The tube was always 

 allowed to remain at least three hours in a desiccator near the balance 



iRichards, Proc. Amer. Acad., 26, 242 (1891). 

 2Richards, J., Amer. Chem. Soc., 22, 144 (1900). 



