140 HYDRATES IN AQUEOUS SOLUTION. 



* 



The hydrates formed by copper chloride and copper nitrate become 

 more and more complex the more dilute the solution. The change is very 

 regular, except for the most dilute solution of copper nitrate, where the 

 experimental errors are necessarily large. 



. Copper sulphate gives very small lowering of the freezing-point of water, 

 as would be expected. 



The chloride, nitrate, and sulphate of aluminium have been studied, and the 

 results recorded in tables 67 to 69. The freezing-point data are given in figs. 

 14, 17, and 43, the conductivity data in fig. 44, and the refractivities in fig. 45. 



Aluminium chloride and nitrate are especially interesting in the present 

 connection, in that they are the first quaternary electrolytes that were 

 studied. The molecules of these substances dissociate, vielding four ions 



" \i O 



each. Further, they each crystallize with a large amount of water, and we 

 should, therefore, expect a large hydrating power. An examination of the 

 results will show that this is the case. 



Aluminium sulphate, like the sulphates in general, gives comparatively 

 small lowering of the freezing-point of water. 



The chloride and nitrate of chromium have also been studied as other 

 examples of quaternary electrolytes. The results are given in tables 70 to 71. 

 The data are plotted in figs. 17, 28, 29, and 54. 



Chromium chloride forms a series of hydrates containing large amounts 

 of water, and increasing in complexity regularly from the most concentrated 

 to the most dilute solution. The curve expressing the relation between 

 concentration of the solution and the amount of water held in combination, 

 is one of the most regular that was obtained for any substance. 



The results for the more dilute solutions of chromium nitrate are unex- 

 pected. We propose to study further these solutions. Hydrolysis doubtless 

 plays here a prominent role. 



The chloride and nitrate of iron were studied as other examples of qua- 

 ternary electrolytes. The results are given in tables 72 and 73 and plotted 

 in curves, figs. 14, 17, 28, 29, and 30. 



On account of the great hydrolysis which ferric chloride undergoes, and 

 the large time factor in its conductivity, the conductivity measurements were 

 not made with this substance. It was, therefore, impossible to calculate even 

 the approximate composition of the hydrates formed by ferric chloride. The 

 large magnitude of the freezing-point lowerings, however, shows that ferric 

 chloride has great hydrating power. 



The conductivities of ferric nitrate were measured, and the approximate 

 composition of the hydrates formed by it calculated. 



A number of strong mineral acids were brought within the scope of this 

 investigation. They are hydrochloric, hydrobromic, nitric, sulphuric, chromic, 

 and phosphoric acids. 



