36 Studies on Solution. 



In the region of wave-lengths lying on the edge of the infra-red 

 band, A experiences deviations from a constant value, and again these 

 deviations show a certain regularity concomitant with the increasing- 

 molecular complexity of the solvent. In this region A is nearly con- 

 stant for the water solutions, but increases with dilution for the alcohol 

 solutions, the increase becoming greater as the molecular weight of 

 the alcohol increases. 



COBALT CHLORIDE IN THE ALCOHOLS WITH WATER. 



The striking color changes which take place when water is added 

 to an alcoholic solution of cobalt chloride are well known. Donnan 

 and Bassett 1 came to the conclusion that the blue color of certain 

 solutions of cobalt salts is due to the formation of complex anions con- 

 taining cobalt. In an interesting paper by A. R. Brown 2 the disap- 

 pearance of the intense red absorption band, which takes place when 

 the alcoholic cobalt-chloride solution is diluted with water, is attributed 

 to the formation of a complex composed of cobalt chloride and water 

 molecules. A series of ethyl-alcohol solutions containing increasing 

 quantities of water was prepared, and from the measurements of a 

 at the summit of the red absorption band, making certain assumptions 

 for which the original paper should be consulted, Brown has calculated 

 that the complex contains 1 molecule of cobalt chloride associated with 

 about 15 molecules of water. 



The present work yields information concerning the behavior of 

 the edges of two bands. It would have been more satisfactory if 

 the behavior of the tops of the bands could have been studied. The 

 summits of the bands, however, were inaccessible. Brown's calculation 

 was applied to the values of a measured for wave-lengths lying on the 

 edge of the red absorption band. This was done for the cases of the 

 three sets of alcoholic mixtures studied. The calculations gave as a 

 result that with 1 molecule of cobalt chloride there was associated a 

 large number of water molecules. The number varied from 30 to 500, 

 depending on the wave-length and the set of solutions selected for the 

 calculation. It seems, therefore, that one is not justified in applying 

 Brown's calculation to the values of a determined on the edge of the 

 band. It should be stated, however, that the accuracy of the values 

 of a is really not sufficient to do complete justice to the problem. 



COBALT CHLORIDE IN METHYL ALCOHOL WITH WATER. 



Three methyl-alcohol solutions were prepared containing cobalt 

 chloride and water. In table 11, the concentration of the cobalt 

 chloride, denoted by Ci, was 0.5 for each solution. The concentrations 

 of the water, denoted by c 2 , were 2.78, 5.55, and 8.32. The values of 

 a for the pure alcohol and pure water solutions were taken from the 

 work on cobalt chloride in these solvents. 



Mourn. Chem. Soc., 81, 939 (1902). 2 Proc. Roy. Soc. Edinburgh, 32, 50 (1911-12). 



