Dr Thomson on the atomic weight of Nickel 159 



Let us see to which of the constituents of the salt this loss be- 

 longs. 



(1.) The residual liquid from (paragraph 1) was evaporat- 

 ed to dryness, and just as much water added drop by drop to 

 the salt as was sufficient to dissolve it. No sulphate of barytes 

 remained undissolved, nor did muriate of barytes indicate the 

 presence of any sulphuric acid in the liquid. Thus it appears 

 that the loss does not fall on the sulphuric acid. The whole 

 of it was obtained. 



(2.) The yellow salt of (paragraph 2,) before trying its solu- 

 bility in water, was laid upon a quantity of ignited charcoal, 

 and kept in a red heat for five minutes ; but no farther loss 

 of weight was sustained. There is no reason then to suspect 

 that the whole water was not driven off. 



(3.) The liquid from which the nickel had been thrown 

 down by carbonate of soda was concentrated as much as pos- 

 sible, and then put into a crystal tube shut at one end. On 

 looking down through this liquid, (which occupied a space of 

 about four inches in the tube,) a green shade of colour was 

 very perceptible. It is obvious from this that it still retained 

 some nickel in solution. 



Thus it appears that the loss in the analysis was owing to 

 the nickel not being completely precipitated by the carbonate 

 of soda. If we add this loss to the nickel, we have the con- 

 stituents of sulphate of nickel as follows : — 



1 Atom acid, - 5. 



1 Atom protoxide, - 4.25 



7 Atoms water, - 7.876 



17.125 



Thus the atomic weight of protoxide of nickel is 4.25, as I 

 have before shown it to be. 



From the experiments of Berthier there can be no doubt 

 that the atom of nickel weighs 3.25. I have made no experi- 

 ments on peroxide of nickel. My opinion respecting its con- 

 stitution is founded solely on the experiments of Rothoff*. 

 With these experiments the statement of Lassaigne does not 



