of Nickel and its Oxides. 329 



The oxide of nickel obtained then is a compound of, 

 Nickel . . . 6-72 or 3-25 

 Oxygen . . . 3-28 or 1-58 



10-00 



It is obviously the peroxide of nickel obtained by RothofT, 

 and which he showed to be a compound of 1 atom metal 

 and 1^ atom oxygen/'^ If we were to consider the result of 

 this analysis of sulphate of nickel and peroxide of nickel as 

 perfectly accurate, the atomic weight of nickel would be 

 only 3-085. But, I consider my original number, 3*25, 

 founded on the determination of the sulphuric acid in a 

 given weight of the sulphate by double decomposition as 

 susceptible of far greater precision, and, therefore, more to 

 be depended on. Meanwhile, the preceding experiments 

 leave no doubt about the cause of the different atomic 

 weights given to nickel by Berzelius and myself. He has 

 adopted the numbers derived from the experiments of 

 Tupputi and of Rothoff, and these chemists have mistaken 

 the peroxide of nickel for the protoxide. 



It may be worth while to correct my analysis of sulphate 

 of nickel, by changing the peroxide of nickel obtained into 

 protoxide. Reducing the peroxide, on the supposition that 



• As a further corroboration of this constitution I may mention another expe- 

 riment. 10 grains of the same black oxide were mixed with 17-63 grains of a 

 sulphuric acid, composed of 



1 atom acid, . .' 5* 



3 atoms water, 3'375 



8-S75 

 and, therefore, equivalent to 10*525 grains anhydrous acid. The solution took 

 place slowly and with effervescence, but was complete. It was placed under the 

 exhausted receiver of an air pump over sulphuric acid. It crystallized to the very 

 last drop. It was left under the receiver till the crystals had eflEloresced, all except 

 a few large ones in the centre, which continued green and translucent in the 

 middle, though tlie surface had effloresced. The salt weighed 27*5 grains. It 

 was composed of 



Acid 10-525 or 5* 



Oxide of nickel 8-947 or 4-25 



Water 8-028 or 3*813 



Had the large crystals not retained too much water, it is obvious that there 

 would have remained exactly three atoms water ; so that four had escaped. The 

 excess amounted to about two-fifths of an atom. 



This does not prove the oxide to be protoxide, but it shows that the atomic 

 weights of the oxides of nickel are 4*25 and 4*75. 



