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PLUCKER ON THE DETERMINATION OF THE 



table in the eighteenth paragraph with the magnetism of the 

 oxide obtained from it by heating it to strong redness in a furnace, 

 which I shall designate by III., as also with the magnetism of 

 the neutral persulphate of iron in powder, also prepared from it, 

 and which was afterwards dissolved in water. The oxide I. was 

 subsequently prepared from the same hydrate. The results 

 found are contained in the following table : — 



Hydrated peroxide of iron 



Peroxide of iron 



Persulphate of iron 



A. 



grms. 



14-47 

 12-35 

 1310 



c. 



grms. 



7-94 



650-68 



4-95 



D. 



grms. 



0-534 



52-687 



0-379 



21. Since according to the table in the last number the rela- 

 tive magnetic deportment of the protoxide of nickel and its hy- 

 drate, according to our present notions of magnetism, appear 

 contradictory, a separate examination was subsequently again 

 made. On using six elements and the same watch-glass, the 

 following results were then obtained : — 



From the earlier experiments we obtain for the relation of the 

 magnetism of the protoxide of nickel and its hydrate, — 

 544 



180 



we now find for the same, — 

 542 



=3-017 



173 



= 3-132. 



The numbers agree sufficiently. 



Although the protoxide was obtained from the hydrate, it 

 nevertheless appeared to me desirable to convert the same hy- 

 drate, which had been used in the experiments, into oxide, 

 and then to examine it. The above 11-07 grms., immediately 

 after the determination of their magnetism, were heated to red- 

 ness in a platinum crucible for a long time, whereby the weight 

 became reduced to 8-38 grms. The protoxide thus obtained was 

 placed in the same watch-glass, but this it did not now completely 



