OP ARTS AND SCIENCES. 215 



the barium salt was heated for some time with an excess of zinc dust, 

 the filtered solution boiled with the addition of baric hydrate till am- 

 monia was no longer given off, and the excess of baric hydrate precipi- 

 tated with carbonic dioxide. The solution thus obtained yielded on 

 evaporation the barium salt of #-sulphopyromucic acid in satisfactory 

 quantity. Since this salt was very nearly if not quite as soluble in cold 

 water as in hot, its purification could most conveniently be effected by 

 conversion into the acid salt, which was readily soluble in hot water, 

 but sparingly in cold water. 



Baric fi-Sulphopyromucate, BaC 5 H 2 SO G . 3 H 2 0. — ■ This salt is 

 sparingly soluble in hot water, and the hot saturated solution deposits 

 nothing on cooling. By evaporation in vacuo over sulphuric acid, the 

 salt is obtained in clean obliquely terminated plates, which contain 

 three molecules of water. 



I. 1.5356 grm. of the air-dried salt lost, at 160°, 0.2156 grm. H 2 0. 

 II. 1.2179 grm. of the air-dried salt lost, at 160°, 0.1707 grm. H 2 0. 

 III. 0.7448 grm. of the air-dried salt gave 0.4571 grm. BaS0 4 . 



in. 



36.08 



I. 0.7139 grm. of the salt dried at 160° gave 0.5092 grm. BaS0 4 . 

 II. 0.7303 grm. of the salt dried at 160° gave 0.5197 grm. BaS0 4 . 



Calculated for Found. 



BaC\-H 2 SO G . I. II. 



Ba 41.90 41.94 41.84 



If the solution is evaporated at 100°, the salt separates in small 

 clear prisms with oblique truncations, which appear to contain one 

 molecule of water* If the salt is removed while the solution is hot, 

 it contains a somewhat lower percentage of water (IV.) than it does 

 when the solution is first allowed to cool (I., II., and III.). In the 

 latter case it undoubtedly contains a slight admixture of the salt con- 

 taining three molecules of water. 



I. 4.2755 grm. of the air-dried salt lost, at 165°, 0.2510 grm. H,0. 

 II. 2.1345 grm. of the air-dried salt lost, at 165°, 0.1290 grm. H 2 0. 



* In a preliminary paper (Bericlite d. deutsch. chem. Gesellsch., xviii. 2095) 

 the baric ,3-sulphopyromucate was described as containing but one molecule of 

 water. At that time the salt obtained by evaporation at 100° had alone been 

 analyzed. 



