370 IRON, NICKEL, COBALT, &c. 



nese being known, it is easy, from what has been 

 already said, to determine the composition of 

 the native black oxide employed by manufac- 

 turers : 11 black oxide, when heated to redness, 

 Atomic i ose i of oxygen, and become 10 deutoxide : or, 



weight of J ~ 



which is the same thing, 5 '5 black oxide, when 

 deprived of 0*5 oxygen, become 5 deutoxide ; 

 consequently, the atomic weight of native black 

 oxide is 5 %5, and it is obviously composed of 



1 atom manganese 3-5 



2 atoms oxygen 2 



5-5 



This is an oxide not analogous to any of the 

 known oxides of iron, nickel, or cobalt. It has 

 been hitherto distinguished by the name of per- 

 oxide of manganese ; but, as there is reason to 

 believe that manganese forms at least one, if not 

 two additional oxides, it will be better hence- 

 forth to call it tritoxide of manganese. 



*J O 



^" Scheele, m &ny years ago, made a curious 

 experiment with the tritoxide of manganese. 

 He mixed it with caustic potash, and exposed it 

 to a heat sufficiently strong to melt the alkali. 

 The fusion being kept up for some time, a dark 

 green, or blackish mass was formed, which was 

 soluble in water. By degrees, a yellow powder 

 precipitates from this solution, and the liquid 

 assumes a blue colour ; some time after, the co- 



