60 C. W. R. POWELL. 



(Bj Secondary. 



1. Ou 2 S + 2H 2 S0 4 = OuS + CuSO* + S0 2 + 2H 2 0. 



2. CuS + 2H 2 S0 4 = CuS0 4 + S + S0 2 + 2H 2 0. 



He finds that the primary reactions predominate between 

 0° and 270° C. and that the gases evolved contain no 

 hydrogen. Sluiter 1 has gone a little further and proved 

 the presence of nascent hydrogen in the acid by reducing 

 nitro-benzene to aniline. Pickering 2 also classified the 

 reaction as above and in addition pointed out that the 

 formation of nascent hydrogen is not necessitated by the 

 production of cuprous sulphide according to the second 

 primary equation. He states that copper is attacked at 

 19° C. (and probably lower), but that with the exception of 

 a few minute bubbles no gas is evolved until about 130°. 



The action of concentrated sulphuric acid on mercury 

 somewhat resembles that on copper, sulphur dioxide gas 

 and mercury sulphate being formed with no trace of 

 hydrogen at 150° and 200° 0. However in this case it is 

 considered that the acid is directly reduced by the metal 

 without the intermediate formation of nascent hydrogen. 3 



Zinc and iron react similarly to each other, but differ 

 from copper and mercury in producing hydrogen with the 

 concentrated acid. 4 With regard to the evolution of sulphur 

 dioxide gas, Thomsen says that the formation of the gas is 

 hindered by the tendency of the molecules to retain their 

 original configuration, and it is only when the opposition 

 to any change of the status quo is removed by raising the 

 temperature and concentration that the reaction proceeds. 

 Ditte 5 has carried out very complete researches on the 



1 Jour. Soc. Chem. Ind., 1906, p. 318, also Chem. Weekblad, in, pp. 63 

 -66, (1906). 



a Chem. Soc. Trans., 1878, p. 113. 



3 Baskerville and Miller, Jour. Anaer. Chem. Soc, xix, p. 873. 



* Thomsen, Thermochemistry, also Ditte, Ann. Ch. Pharm. xix, p. 66, 

 (1890). * Ditte, loc. cit. I 



