OF ARTS AND SCIENCES. 15 



and 1.0126 grammes of toluol at 24°. Hence the specific gravity 

 of crystallized baric bromide at 24*^ compared with water at 4° is 

 3.852. Xo correction is made for the difference in volume of the 

 weights employed. 



A sample of baric bromide was dried at 200°, powdered very 

 rapidly, transferred to the specific gravity bottle, and heated for a 

 long time at the softening point of glass. After cooling in a desic- 

 cator the weight of the baric salt was found to be 7.6808 grammes. 

 After filling with dr}' toluol, removing the atmospheric pressure, 

 and shaking as usual, the gain in weight was 8.3878 grammes, as 

 a mean of two closely agreeing trials. Since the volume of the 

 pycnometer had slightly altered during the heating, the bottle was 

 remeasured and found to contain 11.3338 grammes of water at 4° 

 (not corrected for the expansion of the glass), and 9.7685 grammes 

 of toluol at 24°. These data give a result for the specific gravity 

 of anhydrous baric bromide equal to 4.794. 



Since the apparatus was not perfect, a new specific gravity bottle 

 was prepared, which gave far more concordant results. With this 

 apparatus 5.7271 grammes of baric bromide, dried for a long time 

 at 200°, were found to displace the same volume as 1.1979 grammes 

 of water at 4°. Here again the salt and toluol were at 24°, and 

 the weights were not corrected for the different volumes of the 

 brass. These figures indicate a specific gravity of 4.781, — not 

 very different from the previous result, but very different from the 

 value obtained by Schiff. The value 4.79 is used in all calcula- 

 tions which follow. 



One hundred parts of water dissolve about one hundred parts of 

 anhydrous baric bromide at ordinary temperatures, and nearly one 

 hundred and fifty parts at the boiling point of water.* The salt 

 was found to be much less soluble in alcohol than one would expect 

 from the literature on the subject. 



A saturated solution in 87% alcohol contains only about six 

 per cent of baric bromide at the ordinary temperature. In ab- 

 solute alcohol the salt is even less soluble. These facts had an 

 important bearing on the methods of purification. 



* See Graham Otto, loc. cit. Also recent experiments here. 



