364 IRON, NICKEL, COBALT, c. 



100 grains of protoxide become peroxide by 

 uniting with 11 grains of oxygen. But 11 2 

 = %%, which approaches very near the oxygen in 

 100 grains of protoxide. 



Atom of From this we see that the oxygen in the prot- 

 cobah. e oxide is to that in the peroxide as 2 to 3. Con- 

 sequently, the atomic weight of peroxide of co- 

 balt must be 4-75, and it must be a compound 

 of 



1 atom cobalt 3-25 



1 atom oxygen 1-5 



4-75 



Thus its composition and weight agree with 

 those of peroxide of nickel ; like that peroxide, 

 it does not appear capable of uniting with acids, 

 nor of entering into any permanent combina- 

 tions like the peroxide of iron. 



SECT. IV. 



OF THE ATOMIC WEIGHT OF MANGANESE. 



THE atomic weight of the protoxide of this 

 metal may be made out from the protosulphate 

 in the same way as the protoxide of iron, nickel, 

 and cobalt. Protosulphate of manganese, when 

 pure, forms large transparent crystals, having a 

 beautiful flesh colour, and the shape of a very 

 oblique rhombic prism, the faces of which meet 



