1813.] a Chemical Knowledge of Manganese. 1.83 



Their specific gravity amounts to 1-834, that of water being 

 1-000. 



At the temperature of 66° they become opake and white. 

 When the crystals are heated to redness in a coated retort, 

 they lose then- water of crystallization, and a white dry mass 

 remains in the retort, which dissolves in water by the assistance 

 of heat. When the fire is raised so high as to melt the retort, 

 an imperfect decomposition of the salt is obtained. Sulphurous 

 acid is disengaged, and some glaceous sulphuric acid is found in 

 the receiver. 1 here remains in the retort a mixture of sulphate 

 of manganese, and of brown oxide. 



The aqueous solution of sulphate of manganese is neither 

 precipitated by oxalate of potash nor borate of soda. Some 

 chemists, indeed, have obtained a precipitate by means of this 

 last salt, consisting, as they say, of borate of manganese; but 

 this only happens when the borate used contains an excess of 

 alkali, as is the case with the borax of commerce. Pure tarta- 

 ric acid produces no precipitate in this solution. When the 

 liquid into which this acid has been poured is evaporated suffi- 

 ciently, prismatic crystals make their appearance, which have 

 •the properties of sulphate of manganese. Infusion of nutgalls, 

 and the alkaline eliminates and arscniates, produce no change 

 upon the solution of sulphate of manganese. 



The solution is precipitated by the alkaline prussiates, car- 

 bonates, and phosphates, and a white powder is obtained, con- 

 sisting of the oxide of manganese united with the acid of the 

 salt employed. If the sulphate of manganese contains the 

 smallest portion of copper, the precipitate formed by the action 

 of an alkaline prussiate has a peach-blossom red colour. 



Estimate of the Proportion of the Constituents. 



One hundred and fifty grains of the salt were dissolved in 

 water, and decomposed, while hot, by means of muriate of 

 manganese. The sulphate of barytes which separated was care- 

 fully collected, washed, dried, and heated to redness. It weighed 

 1-48' grains. As it appears from Klaproth's late experiments 

 that tli'' proportion of acid in dry sulphate of barytes amounts 

 to 34 per cent., it follows that 148£ grains of the salt contain 

 grains of acid. 



The solution of manganese thus freed from sulphuric acid was 

 precipitated by means of carbonate of potash. The precipi- 

 tate, collected, washed, and dried at the temperature of 80 \ 

 weighed 8.3 J grams, winch, from the preceding experiments on 

 the composition of carbonate of manganese, indicate -b6\ grains 

 of protoxide. 



As the 53 grains of loss must be imputed to the water con- 



