ElvISHA MITCHELL SCIENTIFIC SOCIETY. 5 



persulphide and oxide, the latter being- dissolved in 

 the acid. 



Maumene^ claimed that his black residue contained 

 four different bodies; copper subsulphide and three 

 oxysulphides, Cu0.2Cu2S or CujSoO, Cu0.2CuS or 

 CU3S2O, and CuO.CuS or Cu,SO. 



In my analyses, as also in Pickering"'s, the sum of the 

 percentag-es of copper and sulphur alwa^^s approxi- 

 mated 100. In one experiment I did find a body whose 

 composition approximated Cu0.2Cu2S. I shall speak 

 of that apparent exception further on. 



Calvert and Johnson'^ performed some experiments 

 on the action of strong and dilute sulphuric acid on 

 copper at temperatures from 130" to 150'^ C. They 

 noted the formation of the subsulphide and claimed it 

 was due to the liberation of free sulphur which after- 

 wards combined with the copper direct.^ There was 

 evidently something- very wrong- in their observations, 

 for they failed to note any action below 130" C. Bar- 

 ruel in 1834 had noted that action took place at the 

 temperature of the air. I have noted the action at 0" C. 



According- to Andrews 



Cu+SOg-CuO-f-SOs 

 CuO + H,S04=CuS64 + H,0 

 are the correct formulas, SO3 existing- at the tempera- 

 ture necessary for the reaction, and the insoluble resi- 

 due being- the oxide. That would do if the reaction 

 occurred only at those higher temperatures, whereas it 

 occurs as well at 0" C. Besides this the undissolved 

 residue is not the oxide at all, as he says it is, but 



1 Ann. Chira. Phys.. 1846, 3rd Series. 18. 311: Traite de chiniie g-enerale. Pelouze 

 et Fremy. 2nd Ed.. I, 388. 



2 J. Chem. Soc. 19. 438. 1866. 



3 Pickering- proved thi.s impossible. The amount of sulphide produced was not 

 increased by adding sulphur direct to the experiment. 



