I v.— C H E M I S T R Y. 



Abt. LII. — On an Allotropic Form of Zinc and Cobalt Salts. 

 By William Skey, Analyst to the Geological Survey Department. 



[Read before the Wellington Philosophical Society, ith December, 1880.] 



In testing some ores for certain metals, I obtained reactions with both the 

 ferro- and ferri-cyanide of potassium, which, according to our present know- 

 ledge, indicated the presence of lead and copper, although further analytical 

 processes showed both metals to be altogether absent. 



Upon taking a retrospect of my operations throughout, I found that the 

 solution which I had prepared for my tests were either uniformly alkaline 

 or, if acid, had been at one time in an alkaline condition. The idea therefore 

 occurred to me that alkahes modify the basic portion of these salts — that is, 

 their metallic oxides, and that the forms to which they are thus modified 

 possess sufficient stability to enable them to withstand the disintegrating 

 effect of acid ; and upon testing the matter, facts were elicited which, as will 

 be seen, conclusively prove that this idea is correct. Thus I found — 



1. That a solution of any zinc-salt alkalized with a fixed alkali, even 

 at a common temperature, and then acidified with nitric, sulphuric, hydro- 

 chloric, or acetic acid, gives, upon the addition thereto of potassic-ferri- 

 cyanide, a yellow precipitate, which shortly turns white, or else a white 

 precipitate at once, instead of the brownish one which all text-books on 

 chemistry teach us to expect. 



2. That the solution thus prepared with either hydrochloric or sulphuric 

 acid afford the brownish precipitate with a ferri-cyanide after being boiled 

 for a short time, or after being kept two or three weeks in the dark or in 

 light. 



3. That the solution with nitric acid, after boiling, gives a yellow preci- 

 pitate with the ferri-cyanide. 



4. That the solution with acetic acid, when boiled, still gives the white 

 precipitate with this salt. 



5. That the white precipitate produced in the above operations is the 

 ferro-cyanide of zinc ; not the ferri-cyanide, as would be anticipated. 



6. That a solution of cobalt when boiled with ammonia in excess affords 

 with potassic ferro-cyanide, a precipitate which is of a rich brown colouy 



