RICHARDS AND FRAPRIE. MANGANOUS SULPHATE. 



511 



and the residue was ignited in the fashion already described. In order to 

 make certain that no transition had occurred during the experiment, the 

 crystal-water contained in the solid phase left over after the saturation 

 was always determined. Below are the data thus obtained. 



The Solubility of MnS0 4 .5H 2 at 25°. 



Cottrell found 64.78 as a mean of two closely agreeing determinations, 

 but the time allowed for saturation was only 2.2 hours. The probable 

 reason for his slightly lower result will be discussed below. 



The solubility of the tetrahydrate is recorded on the following page. 



The solid material taken from the tubes in Determinations 7 to 10 

 contained as much as 4.3 molecules of water for each MnS0 4 , but it was 

 nevertheless probably the designated hydrate containing included mother 

 liquor. The greater solubility of the pentahydrate at 30° would certainly 

 involve the solution of any accessible pentahydrate. The salt remaining 

 from determinations 11 and 12 contained 4.03 molecules of water. 



The results at 30.15°, giving an average of G6.38, correspond almost 

 exactly with Cottrell's figure 66.43 at 30° ; but in this case his time of 

 saturation was increased to an average of three hours, while ours was not 

 much lono-er. Hence close correspondence was to have been expected, 

 and the figures mutually support one another. The slight difference may 

 be due to a residual trace of water in Cottrell's salt. 



