Ohemical Constitution of Saline Solutions. : 261 
The Molecular Weight of Anhydrous Haloid Salts. 
In order to ascertain whether the remarkable difference in colour between 
the hydrated and the anhydrous cupric bromide was due to polymerisation of 
the latter, a determination of its molecular weight was made by means of 
Beckmann’s (boiling point) apparatus. 
J) 
Ii = 100 x ° AG, =o 
The solvent used was alcohol of 99°56 per cent. by weight; therefore, con- 
taining less than 0°5 per cent. water. ‘The constant ¢ for alcohol is 11:5. The 
jacket, as well as the inner tube, was charged with this alcohol. The temperature 
in the jacket was 77°°5 C.; the temperature in the tube, before adding any of the 
cupric bromide, was indicated at 1°64 on the scale of the thermometer. Four 
separately weighed quantities of the salt were added to the alcohol. 
Grs. Temperature. Rise. 
Ise 5 o OSGeo Ibmipall, 5 5 o IGA _ 
Qnd, . . 0:4810 ASHER 1S) o o IP*Bil 0:17 
Orda OLd05, 55 MM. « BOs 0:24 
4th, . . 0:2815 we OTdS | ea dD 0:19 
, 4th,. . 2°39 0-15 
14970 0°75 
_ 100 x 11:5 x 1:497 
~  -10°615 x 0°75 
= Q16°7 
M calculated = 223°52. 
Calculations were made from individual quantities, and the following numbers 
were obtained :— 
Molecular Weight. 
Wie 9 6 0 0 0 Bae) 
Ro 5 «0 o «o Wii 
BR 6 6 o o, 0 Pell 
4th. . . . . 2033 
Mean, . 219:9 
Found, 219:9. Calculated for CuBr,, 223°5. 
It is quite evident that CuBr, is the formula for cupric bromide. 
This determination was made in my laboratory by Mr. J. A. Cunningham, B.A. 
Schmujlow determined the molecular mass of cuprous bromide by dissolving 
it in pyridin; his numbers agreed with the formula CuBr, but not with Cu,Br. 
Cupric chloride, in the same way, was found to be CuCh.* 
* Zeitschrift fiir Anorganische Chemie, vol, 15, p. 18, 1897. 
TRANS. ROY. DUB. S0C., N.S. VOL. VIT., PART VIII, 20 
