ON MANGANESE 77 



SECTION XXXIII. MANGANESE UNITED WITH PHLOGISTON. 



In order to obtain the manganese in this state pure, 

 it ought to be precipitated from limpid colourless solutions 

 by alkali of tartar. The shortest way to obtain it in 

 this manner has been already mentioned (Sec. xix.). It 

 is white like chalk, and I shall call it for the future 

 plilogisticated manganese. That this precipitate contains 

 phlogiston has been already evinced by several experi- 

 ments ; and it has been likewise mentioned that it loses 

 its white colour by calcination in an open fire. The 

 same circumstance is observed when the solution of 

 manganese is precipitated by fixed or volatile caustic 

 alkalies ; for thus a white precipitate is obtained, which, 

 when exposed to the air, soon grows dark brown, but 

 retains its colour when kept in a close glass vessel. The 

 manganese, however, precipitated by fixed vegetable alkali, 

 retains its white colour in the open air. The reason of 

 this is, because it is united not only with phlogiston, 

 but likewise with aerial acid; the precipitate is con- 

 sequently, properly speaking, a salt. No solution of 

 manganese in acids is decomposed by air alone; whence 

 it appears that the acids enhance the attraction of 

 manganese for phlogiston. The manganese, therefore, of 

 which Mr. Einman speaks in his essay, must be a white 

 manganese prepared by art. 



SECTION XXXIV. 



(a) If you dilute a solution of manganese with a good 

 deal of water, and afterwards precipitate it with caustic 

 alkali, the precipitate from the very beginning is brown, and 



