26 .JOURNAL, OF THE 



Pickering-^ however stated that "sulphuric acid attacks 

 copper at all temperatures from 19° C.,' (and probably 

 even still lower) upwards." 



First Experiment. — Copper ribbon in strips, 1 x 3-4 

 cm., was submerg-ed in concentrated sulphuric acid in a 

 clean g-lass stoppered flask for a month. At the end of 

 that time not only were there white crystals of an- 

 hydrous copper sulphate clinging- to the sides of the con- 

 taining" vessel, but there wasa very appreciable amount of 

 brownish black cuprous sulphide and sulphur dioxide was 

 easily detected by its strong- odor when the vessel was 

 opened. 



Andrews^ states "that in the presence of air sulphuric 

 acid is attacked by copper at ordinary temperatures, but 

 without reduction of the acid. The reaction must take 

 place according- to the equation, 



2Cu+0,+2H,SO, = 2CuSO,+2HA 



Formerly the author* stated that thetpresence of the 

 oxygen of the air when it comes into contact with the 

 copper in the acid has g-reat influence on - the reaction. 

 Fifty years ag-o, Maumene'' proved that when a.current of 

 ox3'gcn g-as was passed throug'h the boiling- acid, the 

 amount of insoluble residue, c. §., cuprous sulphide, was 

 diminished, that is, less than there would be formed if 

 the experiment were carried out with a current of carbon 

 dioxide. The copper must be directly opposed to the ox- 

 yg-en by only ]xirtial submersion or the bubbling- of the 

 air against or around the submerg-ed copper; but the air 

 in a confined ^pace, not at all in contact with the copper, 

 but. separated by a thick layer of concentrated sulphuric 

 acid, has little or no effect. 



Yet grant that the oxyg-en of the air (volume of air 



1 /. Chem. Soc, Trans., 1878, 113. 



2 J. Am. Chem. Soc, 18, 252. 



3 Ibid 17-912. 



4 Am. Chem. Phys. 1840 [3], 18. 311. 



