1822.] Yelloiv Copper Ore. 301 



On examining Mr. Chenevix's process, it will be seen that he 

 neglected to examine the nitric solution of the copper and iron 

 for sulphuric acid, which must have been formed while the 

 nitric acid was dissolving these metals, and the quantity of sul- 

 phur was determined merely by weighing the portion remaining 

 unacidified. This circumstance will account for a part at least 

 of the deficiency which Mr. Chenevix has attributed to oxygen ; 

 and further, to prove the iron exists in the state of oxide, he 

 says, that the greater part of the iron, but none of the copper, is 

 dissolved in muriatic acid. I must confess that I have obtained 

 different results. After long boiling in muriatic acid, the ore 

 lost only seven per cent, and of this a part was copper. 



I found that this ore contained a little arsenic, but I did not 

 discover traces of any other metal, excepting iron and copper. I 

 performed the analysis in the mode already described, and 

 obtained from 100 grains, 1*1 of insoluble earthy matter, 254-2 

 of sulphate of barytes, 44 of peroxide of iron, and 39 of peroxide 

 of copper ; and according to what has been already stated of the 

 .composition of these substances, the ore consists of 



Sulphur 34-46 



Iron 30-80 



Copper ,... 31-20 



Earthy matter 1-10 



Arsenic and loss 2-44 



100-00 



Now these proportions differ, excepting in the quantity of 

 copper, most materially from the results of Mr. Chenevix ; but 

 they agree so nearly with those obtained by Gueniveau from 

 the amorphous and by myself from the crystallized variety, that I 

 trust it will be evident that all the varieties are similarly consti- 

 tuted; and I shall now attempt to show their atomic constitution. 



A compound of two atoms of protosulphuret of iron and one 

 atom of persulphuret of copper, would consist of 



4 atoms of sulphur 16 x 4 = 64 



2 atoms of iron 28 x 2 = 66 



1 atom of copper = 64 



184 

 And 100 parts will give 



Sulphur 34-78 



Iron 30-44 r/ 



Copper 34-78 



100-00 



With respect to the crystaUized yellow copper ore, it will be 

 «een that if we neglect the arsenic, lead, and earthy matter, as 



