ORIGIN OF SOME ORgS OF COPPER. 175 



Of course the iron-pyrites was considerably attacked ; but 

 there was no separation of free sulphur. Free hydrochloric 

 acid was also present^ but not in sufficient quantity to dis- 

 solve the small quantity of cuprite formed on the tube. 

 The insoluble crystallized cuprous chloride was carefully 

 washed in distilled water in order to free it from the sub- 

 stances already mentioned, then placed in another glass 

 tube, covered with distilled water, and the tube sealed up 

 and heated for seven days in an air-bath at temperatures 

 varying from i6o° to i8o°. On the second day a very 

 marked amount of a bright-red substance had already 

 formed on the sides o£ the tube, and here and there minute 

 green spots of a substance somewhat resembling atacamite 

 (CuCl2,3CuHO + /rHiO) in colour. This tube was heated 

 at the temperatures given for about two weeks, when it was 

 observed that although the red deposit did not increase in 

 quantity, the cuprous chloride was slowly undergoing de- 

 composition, a black powder having separated out. On 

 opening the tube a smell of hydrochloric acid was perceived. 

 The liquid portion in the tube was poured out, and the 

 solid portion (which principally consisted of unaltered 

 cuprous chloride crystals with a little of the dark-coloured 

 powder) well washed with water. By levigation it was easy 

 to separate the powder from the crystals and to submit it 

 to a further examination. In order to free it completely 

 from cuprous chloride, it was heated in a beaker with a 

 solution of ammonium sulphate in water, which dissolved 

 out all the cuprous chloride and left the powder intact ; 

 and the latter, on being dissolved in nitric acid, did not 

 give any reaction for chlorine, whilst the presence of copper 

 was very evident ; hence there is scarcely any doubt about 

 this substance being cupric oxide. The liquid portion 

 contained free hydrochloric acid and cupric chloride. 

 When the red deposit first commenced to form upon the 



