Manchester Memoirs, Vol. xlviii. (1904), No. 9. 



IX. An Interesting Reaction of Copper Salts. 



By Edmund Knecht, Ph.D., F.I.C. 



Read December i^th, igoj. Received February i^th, 1^04. 



As is well known, the salts derived from titanium 

 sesqui-oxide, TijOg, are powerful reducing agents. More 

 than fifty years ago, Ebelmen, who was the first to 

 describe the chloride, drew attention to the fact that the 

 aqueous solution of this salt was capable of reducing gold, 

 silver and mercury from their salts, while, according to 

 the same authority, cupric salts are thereby reduced to the 

 cuprous and ferric salts to the ferrous condition ; on this 

 latter reaction I have based a method of estimating iron 

 in the ferric condition which is both rapid and accurate. 



By the addition of titanous chloride to the solution 

 of a cupric salt, I find that in the first instance a reduction 

 takes place in the sense alluded to by Ebelmen, i.e., 

 cuprous chloride is precipitated, but on adding excess of 

 the titanium solution, the white precipitate is redissolved 

 and after standing for some time, or better still by 

 warming, metallic copper is precipitated. The reaction, 

 which only takes place in presence of considerable 

 excess of the titanous chloride, is however incomplete ; 

 it is in fact a reversible one, and a method of producing 

 the titanous salt is based upon the action of metallic 

 copper on the tetrachloride. 



But if titanous sulphate is employed in place of the 

 chloride and the copper solution is not too dilute, instant 

 precipitation of metallic copper takes place, even when 

 the reagent is not added in sufficient amount to form a 

 cuprous salt. By adding excess of the reagent, the whole 



March 17th, jgo^.. 



