84 Examination of the Peroxide of Manganese. 



it upon analysis gave but 92.857 per cent, of rnanganoso-man- 

 ganic oxide, while the first forms 100. 



Cyanogen. — When cyaniiret of potassium is added to a solu- 

 tion of a per-salt of manganese, the cyanuret is precipitated under 

 the form of an extremely fine greyish green powder, which re- 

 mains suspended in the liquid for some time. 



^ul-phuric add. — The persulphate may be formed by digest- 

 ing the black oxide in sulphuric acid for several days in the cold, 

 or when peroxide is placed in dilute acid, it is formed in a few 

 hours, but when the peroxide is used, there is a greater excess 

 of acid. This solution is of a beautiful carmine red, but if the 

 oxide be that precipitated from the permanganate of potassa, the 

 solution has somewhat of a violet tinge. It has so great a ten- 

 dency to convert itself into protosulphate, that it can neither be 

 evaporated nor crystallized, and it cannot be kept for any time, as 

 it is decomposed in the coiu'se of two or three weeks. This 

 change may be accelerated by the addition of alcohol. 



Sulphate of manganese and potassa. — This salt, which is the 

 manganese-alum, may be formed, according to Mitscherlich, by 

 adding a concentrated solution of sulphate of potassa to one of 

 persulphate of manganese. It crystallizes of a violet brown color, 

 and is decomposed by the addition of water. 



If bisulphate of potassa be digested upon deutoxide of man- 

 ganese, there is a strong action, which results in the formation of 

 a double salt, which, upon evaporating, remains under the form 

 of a somewhat crystalline mass of a dirty white color, and a 

 pleasant acid taste ; it reddens litmus paper, and shows the reac- 

 tion of the peroxide with yellow prussiate of potassa, and does 

 not seem to be decomposed by water ; but it is most likely the 

 manganese-alum of Mitscherlich. 



Nitric acid. — When nitric acid is digested upon peroxide of 

 manganese, it does not form a per-salt, but the nitrate may be 

 made by adding nitrate of lead to the persulphate of manganese, 

 until they are both neutralized. 



Hydrochloric acid. — If this acid be digested upon per or deut- 

 oxide of manganese, there is a perchloride formed of a dark 

 brown color, and which decomposes immediately by the applica- 

 tion of heat, or in a week or two, in the cold. There then re- 

 mains protochloride, while chlorine is evolved. When evapora- 

 ted to dryness, we obtain crystals of protochloride of a fine pink. 



