ANALYSIS OF ORES OF COPPER.

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The best verditer is at present made only by the refiners, theyobtain the nitrous solution of copper at a cheap rate during theprocess of parting; the value of the article not admitting of thedirect application of nitrous acid to copper. The common ver-diter is made by decomposing sulphate of copper by means oflime. A comparative analysis of both articles has shown thatthe verditer obtained in this manner is always contaminated witha considerable quantity of oxid of iron and sulphate of lime;both admixtures arising probably from the impurity of the sul-phate of copper employed, and the difficult solubility of the sul-phate of lime formed in the process. These objects are wellworthy of being attended to, for the article is of considerablecommercial importance.

ANALYSIS OF ORES OF COPPER.

In order to analyze sulphuret of copper, let one part of theore, reduced to powder, be digested, or extracted, with threeor four of nitric acid by heat, as long as it will take up any ofthe ore; then filter the whole, and wash the insoluble residue,which for the greatest part consists of sulphur. Its quantity maybe ascertained by subliming it by heat, or by burning it in theopen air. It becomes thus partly converted into sulphuric acid.The residue may be diluted with water, and then decomposedby the addition of nitrate of barytes. The insoluble precipitate,when dry, contains 14.5 of sulphur.

In order to separate the iron, let the solution be boiled downto dryness, re-dissolved in nitric acid, and evaporated to drynessagain repeatedly, the iron will then be separated in the form ofa red oxid when water is added to the solution. To ascertainthe quantity of copper which was contained in the ore, the solu-tion from which the iron is separated must be decomposed bythe addition of a solution of potash. The precipitate, after beingdried in a red heat, is black oxid of copper. One hundred partsof it contain 80 of metallic copper.