1836.] 



Miscellanea. 



156 



much iron, which, on solution in an acid, appears in the form of a yel- 

 low ochre. Ten per cent, of quartz was separated from this specimen 

 on pounding it roughly, before setting it apart for analysis. 



" No. 2. A parcel of the same weight is labelled "Bungeral Mettah" 

 and is the species stated to be found in clustered nodules in the alluvi- 

 um, of rounded exterior, as though they had been detached from their 

 original site, and reburied here. The ferruginous matrix of this ore, 

 on solution,, assumes the appearance of a dark-red oxide. It is the 

 same probably as that of Dr. Thomson's specimen. The carbonate of 

 copper runs through it in veins, but the mixture of sulphuret of iron 

 and perhaps of copper with the oxide, gives the whole a dark arenace- 

 ous texture. 



"No. 3. The richest ore of the three is at the same time the most 

 abundant, and promises to yield the safest return, as it runs in unbroken 

 veins. This ore is a combination of carbonate and sulphuret, the for- 

 mer intermixed with the latter, but readily distinguishable from it, as 

 the sulphuret is crystallized, and has the grey metalic lustre of galena. 

 The specific gravity of this ore is 3*77, being intermediate between 

 that of the carbonate, 3*2, and the sulphuret, 4'5. 



" The analysis was conducted for the sake of expedition on separate 

 parcels of 100 grains each, in lieu of attempting the separation of the 

 ingredients from a single parcel. Some variation may thus be in- 

 duced from the irregularity of the ore; but, on the whole, the results, 

 ought to be more trust-worthy. Thus : the carbonic acid was estimat- 

 ed by the loss of weight on digesting 100 grains, finely pounded, in 

 dilute nitric acid. The water, (for none of these ores was found to be 

 anhydrous,) by heating in a glass tube, removing the aqueous vapour 

 by bibulous paper, and ascertaining the loss. As the ore generally 

 lost its green colour by this operation, it is possible that a portion of 

 carbonic acid was also driven off. Calcination in an open dish, in the 

 muffle of an assay furnace, gave a loss, which was compounded of that 

 of the carbonic acid and the water. Calcination drives, off the sulphur 

 also, but the equivalent of oxygen, which replaces it, being of precisely 

 equal weight, this operation affords no test of the quantity of sulphur 

 present— In fact, not expecting from Dr. Thomson's analysis, to find 

 sulphur in the Nellore copper ore, I at first neglected the precautions 

 necessary for its separation. This was accordingly effected on other 

 samples, by boiling in strong nitric acid, which from its heat, caused 

 part of the sulphur in a pure state to rise in fused globules to the 

 surface : while a portion, being oxygenated^ was afterwards separated 

 by precipitation with barytes. 



" The quantity of copper was most conveniently estimated from the 

 black oxide taken up from the calx by dilute nitric acid. It was also 

 obtained directly from other samples by reduction of the oxide with 

 charcoal and borax. — The iron and pyrites were deduced from the 

 difference between the residue in the cold solution, and that from the 

 hot dissolution in strong acid of another parcel, before calcination. 



