OP ARTS AND SCIENCES. 213 



I. 1.1659 grm. of the salt dried at 130° lost, at 200°, 0.0480 grm.H 2 0. 

 II. 0.4608 grm. of the salt dried at 130° gave 0.3798 grm. BaS0 4 . 

 III. 0.5175 grm. of the salt dried at 130° gave 0.4256 grm. BaS0 4 . 



Calculated for Found. 



Ba 3 (C 4 HS0 7 ) 2 . 3H 2 0. I. II. HI. 



2H 2 4.23 4.12 



Ba 48.29 48.45 48.35 



In the sulphuric acid determinations given above, the baric sulphate 

 was precipitated in the presence of large quantities of sodium and 

 potassium salts. Although it was purified in the usual way before 

 weighing, the results are undoubtedly still somewhat too high. 



Argentic Sulphofumarate, Ag 3 C 4 HS0 7 . x H 2 0. — On adding a solu- 

 tion of amnionic sulphofumarate to an excess of argentic nitrate, the 

 silver salt is thrown down as a heavy curdy precipitate, which fre- 

 quently becomes crystalline on standing. It is very sparingly soluble 

 in cold water, somewhat more readily in hot. The air-dried salt con- 

 tains water, a part of which at least it loses at 100°. At 110° it loses 

 more rapidly in weight, but decomposition ensues at the same time. A 

 sample of the salt which had been dried for some time at 100°, but 

 which was still losing very slowly in weight, was analyzed with the 

 following results : — 



I. 0.4448 grm. of the salt gave 0.4673 grm. AgBr, and 0.1933 grm. 

 BaS0 4 . 

 II. 0.4834 grm. of the salt gave 0.2933 grm. Ag. 



The air-dried salt had already lost at 100° about one molecule of 

 water. 



1.0317 grm. of the air-dried salt lost, at 100°, 0.0368 grm. H 2 0. 



Calculated for 

 Ag 3 C 4 HS0 7 . 2 H 2 0. Found. 



1 H 2 3.26 3.57 



The air-dried salt, therefore, appeared to contain two molecules of 

 water. The analysis of a second preparation of the air-dried salt gave 

 substantially the same ratio between silver and sulphur, and yet showed 

 that the salt contained a lower percentage of silver. 



