530 MANGANESE. 



Manganese oxidates readily in air, soon falling down as a black 

 powder; in water it occasions a disengagement of hydrogen gas. 

 It is best preserved in naphtha, like potassium, or over mer- 

 cury. Manganese possesses five degrees of oxidation, with two 

 intermediate or compound oxides. 



OXIDES OF MANGANESE. 



Protoxide or manganous oxide Mn O . 



Deutoxide or manganic oxide Mn 2 O 3 . 



Peroxide .... Mn O 2 . 



Red oxide .... Mn 3 O 4 , or Mn O+Mn 2 O 3 . 



Varvicite . . . . Mn 4 O 7 , or Mn 2 O 3 + 2Mn O 2 . 



Manganic acid . . Mn O 3 . 



Hypermanganic acid . . Mn 2 O 7 . 



Protoxide of manganese, Manganous oxide ; MnO, 445.9 or 

 35.72. This is the oxide existing in the ordinary salts of man- 

 ganese, which are isomorphous with the salts of magnesia. 

 It may be obtained by fusing at a red heat in a platinum cru- 

 cible, a mixture of equal parts of pure chloride of manganese 

 and carbonate of soda, with a small quantity of sal ammoniac. 

 By the reaction between the first mentioned salts, chloride of 

 sodium is produced and carbonate of manganese, which is de- 

 composed at a red heat, leaving the protoxide of that metal. 

 The hydrogen of the sal ammoniac reduces to the state of prot- 

 oxide, at the same time, any peroxide which may be formed by 

 absorption of oxygen from the air. Any one of the superior 

 oxides of manganese, in the state of a fine powder, may be con- 

 verted into protoxide by transmitting hydrogen gas over it, in 

 a porcelain tube at a red heat ; the peroxide obtained by igniting 

 the nitrate of the protoxide of manganese is recommended by 

 Dr. Turner as the most easily deoxidated. The protoxide of 

 manganese is a powder of a greyish green colour, more or less 

 deep. When obtained by means of hydrogen at a low tempe- 

 rature, it absorbs oxygen from the air, soon becoming brown 

 throughout its whole mass, and is, indeed, sometimes a pyro- 

 phorus ; but when prepared by hydrogen at a high temperature, 

 or prepared by means of an alkali, this oxide is permanent. 

 It dissolves readily in acids, and is a strong base. When an 

 alkali is added to a solution of its salts, protoxide of manganese 

 is precipitated white, as a hydrate, which immediately absorbs 



