144 Chemical Activity of Free and Semi-Combined Water. 



All the salts studied, with the exception of sodium sulphate and 

 perhaps also magnesium sulphate, have in the case of the greater con- 

 centrations a retarding influence on the hydrolysis. This retardation 

 diminishes as the salt solution becomes more and more dilute. With 

 sodium sulphate solutions the reverse is true the more concentrated 

 the solution the greater is the accelerating effect. This is also true 

 to a certain extent with magnesium sulphate, although the effect is 

 not so pronounced. 



In the case of both magnesium salts studied, magnesium chloride 

 and magnesium sulphate, it was difficult to get clear, clean-cut results. 

 In titrating the acetic acid with the alkali in the presence of these salts 

 a good end-point could not be reached. The color of the indicator, 

 phenolphthalein, appeared to be masked, especially in the more con- 

 centrated solutions. 



All the non-hydrated salts studied have a hindering effect on the 

 hydrolysis. The amount of this hindrance under the same conditions 

 is practically the same for the four salts studied, there being at no time 

 a variance of more than a few per cent. With the most dilute solutions 

 studied, quarter-molar, the results for the decomposition are practically 

 the same as for pure water. 



The hydrated salts, with the exception of magnesium chloride, all 

 give results for the decomposition greater than those of the non- 

 hydrated ones, while with the more dilute solutions there is an appre- 

 ciable acceleration of the hydrolysis of the acetic anhydride over that 

 due to pure water alone. Sodium sulphate and magnesium sulphate 

 at all concentrations studied have a very marked accelerating effect 

 on the hydrolysis. Greater concentrations of these salts were not used 

 for the reason that they do not mix with the anhydride at once on 

 simple shaking. Calcium chloride, strontium chloride, and barium 

 chloride also have an accelerating influence on the hydrolysis in the 

 more dilute solution. Magnesium chloride acts as do the non-hydrated 

 salts, having a retarding influence at all dilutions. 





