It is evident tliat a difference of 30^ causes very little 

 difference in the rate of precipitation, and probably the 

 point of equilibrium is only very slightly shifted by change 

 in temperature, but the latter point has not yet been 

 determined. 



A solution of zinc sulphate was next used, in order to 

 determine the part played by the acid. The method 

 employed was essentially the same as that previously 

 described, namely, fractional precipitation and the deter- 

 mination of the zinc and free acid in the several frac- 

 tions. The rate of the gas was, as before, about four liters 

 per hour. It w^ill be observed that the precipitation is 

 practically complete at the end of seven hours, even 

 though 4.47 per cent of free sulphuric acid was present. 

 In general the curve closely resembles that of the chloride. 



SKRIES VII. 



In order to find the point of equilibrium, if possible, a 

 solution containing more acid was used. As may be 

 observed in Series VIII, precipitation was still going on at 

 the end of ten and a half hours when there was 5.25 per 

 cent of free acid in the solution. The results are shown 

 graphically in curve Y. 



