1813.] a Chemical Knowledge of Manganese. 267 



When heated in a crucible, the acid is disengaged, and a 

 brown oxide remains, which may be treated with acids, without 

 emitting any smell of sulphurous acid. 



To determine in some measure the proportion of the consti- 

 tuents of this salt I treated 50 grains of it with very diluted 

 sulphuric acid, and when all the sulphui'ous acid was separated, 

 mixed the liquid with more water, and precipitated the manga- 

 nese by carbonate of potash. The carbonate of manganese ob- 

 tained weighed, after being washed and dried, 36 grains, which 

 is equivalent to 20-^ grains of protoxide. Hence 100 parts of 

 sulphite of manganese are composed of 



Protoxide 40*2 



wtL} ™* 



100-0 

 VII. Action of Muriatic Acid on Manganese. 



(A.) On the Metal. 



The metal is readily dissolved by muriatic acid of every degree 

 of concentration with the evolution of hydrogen gas, and, when 

 the acid is not too much diluted, with the production of consi- 

 derable heat. 



The solution when concentrated has a colour approaching 

 rose-red, and deposites crystals of a similar colour. 



(B.) On the Protoxide. 



The pure protoxide dissolves in this acid quietly, and the 

 carbonate with a strong effervescence. The solution has a rose- 

 red colour. 



Chemists have hitherto affirmed that this salt cannot be pro- 

 cured in the state of regular crystals. I have, however, been 

 able to procure it in as regular crystals as any salt whatever. 

 My method was this: I procured a quantity of concrete salt 

 by evaporating to dryness a solution of manganese in muriatic 

 acid. This I put into a solution, quite neutral, and already 

 evaporated in a cylindrical porcelain vessel till a cuticle had 

 formed on its surface. The vessel was placed for some days, as I 

 have described in a preceding paragraph, in a temperature be- 

 tween 77° and 88°. 



Properties of ctijstallized Muriate of Manganese. 



It crystallizes in very fine, loiigish, thick four-sided table>, 

 both extremities of which are pointed with two plains, and the 



