Messrs. Mills and Hunt on Chemical Equivalence. Ill 

 two equations are apparently related thus 

 tj> e —a+bx } 



where p is some constant to be deduced from the determina- 

 tions. We find, in the case of manganous sulphate, that these 

 relations do in fact hold accurately ; but the results with 

 nickelous sulphate are not in definite accordance with them. 

 We trust on some future occasion to resume the consideration 

 of this subject, which is of primary importance in the theory 

 of precipitation. 



The equations of separate precipitability (as deduced from 

 the separate precipitation experiments) are 



(f) m = -36383 + -9(3951 m, .... (8) 



4> n =-78027+ -95815m (9) 



Here there is no reciprocal relation between the second con- 

 stants, which are indeed identical within the limits of experi- 

 mental error. We infer from these numbers that manganous 

 and nickelous sulphates, when separate, are equallv precipi- 

 table. 



The following are the chief conclusions which we have 

 drawn from our work. 



1. Precipitability is a linear function of mass. 



2. When commixed manganous and nickelous sulphates are 

 precipitated by sodic carbonate, equal weights of them are 

 equally precipitable, the attraction of one of them for the 

 reagent being the inverse of that of the other. 



3. When the above sulphates are separately precipitated by 

 the same reagent, they are equally precipitable, and do not 

 exhibit the inverse function. 



4. There is some evidence that the precipitabilities of the 

 commixed and separate sulphates are mathematically related 

 in a simple manner. 



5. "Within moderate limits, precipitation is not traceably 

 affected by temperature. 



XX. Researches on Chemical Equivalence. — II. Niekdous and 

 Cadmic Sulphates. By Emjtxd J. Mills, D.Sc, F.R.S., 

 and Bebtbam Hlxt*. 



\ 1 / E propose to consider a case in which a metallic sul- 

 ▼ * phate belonging to some other group is compared 

 with nickelous sulphate (the previously employed standard), 

 sodic carbonate being the precipitant. For this purpose we 

 have selected cadmic sulphate — partly because it admittedly 

 * Communicated hy the Authors. 



