MANGANESE. 365 



at angles of about 148 and 32. Its taste is 

 somewhat similar to that of Glauber's salt, but 

 rather more disagreeable ; and like that salt, it 

 acts as a cathartic when taken to the extent of 

 about half an ounce. It is very soluble in water, 

 but is not altered by exposure to the air, whether 

 the atmosphere be dry or moist. 



1. 15-125 grains of these crystals were dissol- Sulphate of 



manganese 



ved in water, and the liquid mixed with a solu- analyzed, 

 tion of 13-25 grains of chloride of barium. A 

 double decomposition took place, and when the 

 sulphate of barytes had subsided, the residual 

 liquid was neither affected by sulphate of soda 

 nor muriate of barytes. From this experiment 

 it follows, that 15-125 grains of protosulphate of 

 manganese contain exactly 5 grains of sulphuric 

 acid. 



2. When 15-125 grains of protosulphate of 

 manganese are heated in a platinum crucible, 

 they melt, and the water of crystallization is gra- 

 dually dissipated. But it is scarce possible, by 

 this process, to drive off the whole water of crys- 

 tallization without allowing some of the acid at 

 the same time to escape. Dr. John, from 15*125 

 grains of this salt, drove off 5 -345 grains of wa- 

 ter. I repeated this experiment with great care, 

 and found that I could disengage 5 '48 grains of 

 water from 15-125 grains of the salt. But if the 

 heat was raised high enough to produce a greater 

 diminution of weight, a portion of the salt was 



