212 Dr. C. R. A. Wright and Mr. C. Thompson. [Mar. 31, 



March 31, 1887. 



Professor STOKES, D.C.L., President, in the Chair. 



The Presents received were laid on the table, and thanks ordered 

 for them. 



The following Papers were read : — 



I. " Note on the Development of Voltaic Electricity by Atmo- 

 spheric Oxidation." By C. R. Alder Wright, D.Sc. y 

 F.R.S., Lecturer on Chemistry and Physics, and C. 

 THOMPSON, F.C.S., Demonstrator of Chemistry, in St. Mary's' 

 Hospital Medical School. Received March 10, 1887. 



It is well known that when metallic copper is brought into contact 

 simultaneously with atmospheric air and aqueous solution of ammonia,, 

 rapid oxidation is set up, the copper oxide formed dissolving in the 

 liquid, producing a blue solution of ammoniacal cupric oxide, or 

 cuprammonium hydroxide. Whilst investigating processes for the 

 manufacture of this fluid (now. used commercially on a considerable 

 scale) we noticed that if the air supply be greatly in deficiency 

 relatively to the bulk of the copper, under certain conditions the 

 solution is but little coloured, containing copper dissolved principally 

 as cuprons, and not as cupric, oxide. This might, perhaps, be antici- 

 pated a priori^ inasmuch as it is well known that blue cupric solution 

 in ammonia, when digested with metallic copper in the absence of air, 

 takes up a second equivalent of copper, becoming colourless cuprous 

 solution ; but further experiments seem to indicate that the production 

 of cuprous oxide under the oxidising influence of a limited supply of 

 air is the primary action, and not merely a secondary result ; in short, 

 that the first step in the change is expressed by the reaction — 



4Cu + 3 = 2Cu 2 0; 



cuprous oxide being formed, which then (under favourable conditions) 

 becomes further oxidised to cupric oxide, thus — 



2Cu 2 + 2 = 4CuO, 



and not by the reaction — 



2Cu + 2 = 2CuO; 



