580 Analysis of Nellore Copper ores. [Oct. 



haps to have prevented the access of air to oxidate the interior. — 

 The sulphur enables us to approximate the correction of this item ; 

 for 12.8 requires 51.5 copper, = 64.3 black or peroxide; and this, 

 added to 22.8, the peroxide of the carbonate, would give 87.7 ; which 

 is 14.0 greater than the actual return from the fire. — Again, deducting 

 the deficiency after calcination (c.) 21.0, from the sum of the three 

 volatile ingredients — sulphur, 12.8 ; carbonic acid, 7.0 ; and water 3.0 

 = 22.8, there remains but 1.8 for the weight of oxygen absorbed in 

 place of the sulphur ; whereas 12.8 are required. — Adding the dif- 

 ference 11.0 to d, we shall have 84.7. This number will be found to be 

 a little in defect from the subsequent results ; while 87.7 is a little too 

 great ; a mean may therefore be adopted. 



From the above data, we may now proceed to extract the simple 

 elements of each specimen of ore : 



No. 1. No. 2. No. 3. 

 I. Metallic copper, calculated from the oxide d, .... 30.2 39.5 69.0 



m. Pure sulphur, from h and i, 0.8 4.5 12.8" 



n. Carbonic acid, less 1 ' 5 th for hygrometric moisture,.. 10.8 13.1 fi.3 



The carbonic acid being supposed to be wholly combined with 

 copper, while the sulphur may be partly united with iron, we may 

 calculate the proportions of the carbonates and sulphurets by means of 

 the scale of chemical equivalents, thus : 



No. 1. No. 2. No. 3. 

 o. The carbonic acid will require copper, 31'4 38"6 18 - 3 



Now in the first two of these, the copper required so nearly agrees 

 with the calculated weight of metal, I. that the latter may be looked 

 upon as existing here wholly in the form of carbonate, and the sulphur 

 as united entirely with iron*. In No. 3, however, we find that the 

 majority of the copper remains ; and knowing the nearly total absence 

 of iron in this specimen, we may conclude it to be a mixture of nearly 

 two parts sulphuKet, with one of carbonate. 



The miner would rest content with the determination of the pure 

 metal in the ore, and would have good reason to be satisfied with the 

 60 per cent. " actual yield" of No. 3, or even with the 30 per cent, 

 of the poorest of the three ores ; but the mineralogist will prefer an 

 exhibition of the component salts of the ores, according to the usual 

 synthetical formula. I may here remark, that the water separated (b) 

 is more than is required to convert the carbonate into a hydrate or 

 ordinary malachite : thus, 



* In the second Analysis of No. 2, however, the copper actually recovered, k, so 

 much exceeds this quantity, that it is evident this ore frequently contains sulphuret, 

 or is of very variable quality. 



