714 Transactions. — Chemistry. 



thus produced/'' Besides that, this free oxygen is greatly 

 condensed as it replaces the combined oxygen of the potash. 



I note here that the vice-president of the Institution ot 

 Mining and Metallurgy at the Geological Museum, Jermyn 

 Street, London, in a paper on "selection action" in the 

 cyanide process, i and which generously deals with much old 

 work of mine, takes the same view^ as Mr. Maclaimn does of 

 electrical action as being the caitse and not the effect of 

 chemical action in the process of Macarthur and Co. So 

 Mr. Maclaurin is in very good company. The paper itself, as 

 may be seen, has been in a large measure anticipated by the 

 two publications of mine referred to, m the parts dealing with 

 the selective action of the patentees of the cyanide process. 



Thirdly, in regard to the assumption that potassium is 

 liberated from potassic cyanide in the experiment figured 3 

 in his paper, I would observe that Mr. Maclaurin omits to 

 give me any proof of this, and that therefore it is impossible 

 for me to think otherwise than that this assumption is alto- 

 gether an unreasonable one. It is true, however, that Pro- 

 fessor Gladstone, Ph.D., P.E.S., and Mr. Alfred Tribe, m a 

 paper read before the Eoyal Society in 1875, | gave the sanc- 

 tion of their names to this idea of a liberation of potassium 

 under circumstances somewhat similar to those we have in 

 Mr. Maclaurin's experiment, but, as these investigators have 

 not replied to the strictures I made thereon, I suppose they 

 have abandoned that idea. However it is, I would, in answer 

 to Mr. Maclaurin's assumption, refer him to these strictures 

 of mine,§ and supplement them by the following remarks : — 



As Mr. Maclaurin well knows, the affinities of this metal 

 (potassium) for oxygen are of extraordinary intensity ; for 

 cyanogen also they are very intense, as a white heat alone 

 does not decompose either compound. To this I think 

 Mr. Maclaurin will agree ; and, if so, how can he assume 

 that the feeble electric current that he supposes to be pro- 

 duced at the surface of the liquid can overturn affinities like 



* More investigations are required in this direction before the reason 

 of this can be thoroughly understood. This action of metals in strong and 

 weak solutions of alkalies is anomalous. Iron in strong HCl coupled 

 with itself in the weak acids did not give me a current, the intensity of 

 the electricity generated in each cell being alike. Copper in sulphuric 

 acid is positive to copper in nitric acid. 



t " On the So-called Selective Action of Very Dilute Solutions of 

 Cyanide of Potassium used in obtaining Gold and Silver from Ores and 

 Compounds," by James Mactear. Read before that institution, Novem- 

 ber, 1895, and first seen by me 17th March, 1896. 



\ " On the Replacement of Electro-positive by Slectro-negative 

 Metals in a Voltaic Cell." Proc. Roy. Soc, Lond., 1875. 



§ "Notes on the alleged 'Replacement of Electro-positive by Electro- 

 negative Metals in a Voltaic Cell,' " by William Skey. Trans. N.Z. Inst., 

 vol. viii., 1875, pp. 343-345. 



