730 PLtJCKEa ON THE DETERMINATION OF THE 



The gray oxide of manganese consisted of very beautiful 

 crystals in powder, in which iron could not be detected by ferro- 

 cyanide of potassium. It appeared, in correspondence with the 

 well-known analysis, to consist of pure hydrated oxide of 

 manganese. Immediately after the experiment, it was heated 

 to strong redness over a spirit-lamp to remove its water of hy- 

 dration. 9'388 grms. lost 1*164 grm. in weight. The loss in 

 weight corresponding to an atom of water would have amounted 

 to exactly 10 per cent. ; that found amounts to 12*40 per cent. 

 This agrees well with the statement of Berzelius, that hydrated 

 oxide of manganese, when heated to redness, becomes con- 

 verted into protoxide of manganese, which would require a loss 

 of 13"2 per cent. Since the heating to redness between the 

 weighings should take place upon the same quantities, it could 

 not be perfectly complete. 



The crystals of the protosulphate of iron were taken out of the 

 solution in which they had formed immediately before the expe- 

 riment, dried in the air upon bibulous paper for half an hour, 

 and then powdered. The powder, moist as it was, was placed 

 in a watch-glass ; hence but very little of the water which the 

 crystals contained could have escaped. 



The solutions of the salts of nickel used in the experiments 

 were prepared by dissolving the hydrated oxide of nickel already 

 mentioned in acids. 



23. From the two previous tables I have calculated the fol- 

 lowing one for the comparison of the intensity of the mag- 

 netism of different substances, both separately, as also in che- 

 mical combination with others, placing the intensity of the 

 magnetism of iron as = 100,000: — 



1. Iron 100,000 



2. Magnetic iron ore 40,227 



3. Peroxide of iron 1 500 



4 II 286 



5. Red hasraatite 134 



6. Micaceous iron ore 533 



7. Hydrated peroxide of iron 156 



8. Brown hrematite 71 



9. Artificial blood- stone 151 



10. Dry persulphate of iron Ill 



11. Green vitriol 78 



