288 Mr. W. Phillips's Description qffwo Ores of Coppei: 



substance be heated in the open air on platina foil, nearly the 

 same effects and appearances are produced, but the residue is 

 black from the superficial oxidation of the copper. If the sub- 

 stance be heated upon carbonaceous matter, or by the reducing 

 part of a blowpipe flame, then a reduction of part of the ar- 

 senious acid takes place, and a metallic residuum containing 

 more arsenic than in the former case is produced, and which 

 is consequently more fusible. 



This substance dissolves entirely in nitric acid, the portions 

 of metal, &c., which are not naturally in the state of oxide, 

 being oxidized at the expense of the acid. When pulverized 

 and acted upon by cold muriatic acid, arsenite and muriate of 

 copper are found in solution, apparently without the evolution 

 of hydrogen, and metallic arsenic remains undissolved. 



I have little doubt that the substance is a mechanical de- 

 posit, and I find it to vary somewhat in composition. SI'S 

 grains being heated carefully in a tube, the loss of water and 

 of arsenious acid was ascertained, and then the metallic resi- 

 duum, weighing 22'4f5 grains, was dissolved in nitromuriatic 

 acid; the sulphuric acid formed was separated by muriate of 

 baryta, and the sulphur in it was ascertained ; the excess of 

 baryta vvas then removed, and afterwards the oxide of copper 

 thrown down by caustic potash, and ultimately the arsenic 

 acid formed thrown down by nitrate of lead. The proportions 

 were as beneath : 



34'5 parts consist of 100 parts consist of 



Water 3-1 8*987 



Arsenious acid . 8*95 25"944' 



f Copper 20-87 60-498 



.,^ I Sulphur 1-057 3-064 



y S Arsenic 0-52 1-507 



t. Trace of iron. 



34-497 100-000 



The manner in which these substances are arranged in the 

 mineral is uncertain, and may be put several ways. It is pro- 

 bably a mixture of metallic arsenic, arsenite of copper, oxide of 

 copper, a little copper pyrites; one or more of these substances 

 being in combination with water. 



Examination of the Arseniuret of Copper, bj/ M. Faraday, Esq. 



Royal Institution, Sept. lOtli, 1827. 

 The specimen you sent me is intermingled with portions of 

 a substance like that before analysed : it also contains por- 

 tions of copper nearly pure. Some of the purest and most 

 uniform parts which I could select, when heated in a small 



sreen 



