2 Taylor, Higher Oxide of Cobalt. 



depend upon the amount of oxygen in the oxide greater 

 than that required by the formuhi CoO. The action of 

 the acid and potassium iodide upon the sesquioxidc, for 

 example, would be as follows : — 



Cop, + 6HC1 + 2KI = 2C0CI + 2KCI + 3H„0 + I,. 

 The amount of iodine liberated could then be determined 

 by titration with a solution of sodium thiosulphate. 



In my former paper I had assumed that the pre- 

 cipitated oxide was the sesquioxide, and referred to it 

 as such. I very soon found, however, that the oxide 

 produced in the above reaction was certainly higher than 

 CojO.., and, on investigation, I found that a considerable 

 number of higher oxides of cobalt have been described 

 by various observers. It appears, in fact, that the genuine 

 sesquioxide is really very seldom obtained by precipita- 

 tion. 



The first description of an oxide of cobalt higher than 

 Co20„ which I have been able to find is by Thomas Bayley, 

 A.R.C.S., Ireland,* who, determining the composition of 

 the oxide by the method indicated above, found that an 

 oxide as high as Co„05 is produced when a solution of 

 sodium hypochlorite is added to a solution of cobalt. 

 Bayley also found that, if the liquid containing the precipi- 

 tate is boiled for some time, the oxide loses oxygen, 

 changing to another oxide which he describes as C012O19 ! 

 More recently, Bayleyf has repeated some of his experi- 

 ments, determining the composition of the oxide by 

 its oxidising action upon ferrous sulphate. He finds, as 

 before, that a h}'pochlorite or hypobromite, at the 

 ordinary temperature, precipitates CoaOc, but that oxides 

 of varying composition are precipitated by other oxidising 

 agents, or by boiling the solution. Incidentally, I have 



* Cheni. News, Vol. 39, 1879, p. 81. 

 t Chem. News, Vol. 82, 1900, p. 179. 



