CONTRIBUTIONS FROM THE CHEMICAL LABORATORY OF 



HARVARD COLLEGE. 



THE SOLUBILITY OF MANGANOUS SULPHATE. 

 By Theodore William Richards and Frank Roy Fraprie. 



Presented by T. W. Richards, March 13, 1901. Received March 21, 1901. 



The solubility of manganous sulphate has been carefully determined 

 within the past year by F. G. Cottrell,* and the present paper is written 

 to confirm in some measure the results of his work. He was able to dis- 

 prove by well-considered experiment the less recent work of Linebarger, f 

 who published a singular series of results resting ujx>n faulty reasoning 

 and an erroneous method of experimentation. In a case of this kind, 

 when authorities differ, the truth is more quickly enforced when it is sup- 

 ported, hence the publication of the present paper. 



The work to be recorded below was done in the spring of 1898, long 

 before the work of Cottrell. It was part of a still unfinished investiga- 

 tion which has as its object the study of the transition equilibria of potassic 

 manganous sulphate. We hope that circumstances may permit the early 

 publication of the remainder of this work, which has been suspended for 

 a time.t 



It was soon found that a much higher temperature was necessary to 

 drive off the water of crystallization of manganous sulphate than has 

 usually been supposed. Linebarger used only 180°, at which tempera- 

 ture at least one molecule of water remains in the salt if it is surrounded 

 by air with the usual proportion of aqueous vapor. The handbooks name 

 210° to 240° as the temperature required, and Cottrell, calling attention 

 to Linebarger's error, used 280°. We found that traces of water still 

 remained after heating for half an hour at 350° in an air bath. In this 

 respect the substance reminds one of cupric sulphate. § The amount thus 

 retained does not much exceed the tenth of a per cent, and the effect upon 



* Cottrell, J. phys. ch., 4, 637 (1900). 

 t Linebarger. Am. Chem. Journal, 15, 225 (1893). 



J A brief statement of the scope and object of this work will be found in 1'roc. 

 Am. Ass. Adv. Sc., 213 (1898). 



§ Richards, Proc. Am. Acad , 26, 240 (1891). 



