Chemical Constitutinn of Saline Solutions. 261 



The Moleculai' Weight of Anhijdrous Haloid Salts. 



In order to ascertain whether the remarkable diffei'ence 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. 



The solvent used was alcohol of 99 'SG per cent, by weight; therefore, con- 

 taining less than 0-5 per cent, water. The constant c for alcohol is ll'o. 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. 



1st, . . 0-3640 Initial, . . . l°-64 — 



2iid, . . 0-4810 After l.^^t, . . 1°-81 0-17 



3rd, . . 0-3705 ,, 2nd, . . 2°-05 0-24 



4th, . . 0-2815 ,, 3id, . . 2°-24 0-19 



„ 4tli, . . 2-39 O-lo 



14970 075 



100 X 11-5 X 1-497 

 ^ ~ 10-615 X 0-75 



= 216-7 

 M calculated = 223-52. 

 Calculations were made from individual quantities, and the following numbers 

 were obtained : — 



Molecular Weiglit. 



1st, 232-0 



2nd, 217-1 



3i-d, 227-1 



4th, 203-3 



Moan, . 219-9 

 Found, 219-9. Calculated for CuBi-,, 223-5. 



It is quite evident that CuBrj 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 CuoBr,. 

 Cupric chloride, in the same way, was found to be CuCl2.* 



* Zeitschrift fill- Anorganisclif Cheniie, vol. 15, p. 18, 1897. 



THANS. ROT. DTJB. SOC, N.S. VOL. Vir., PAET VIII. 2 



