Ebook Mackenzie's Five Thousand Receipts in All the Useful and Domestic Arts

The assay of tin ores in the liquid way was looked upon as impracticable, till Bergmann densed the following method, which is generally successful Let the tin ore be well separated from its stony matrix, b well washing, and then reduced to the most subt e powder; digest it in concentrated oil of vitriol, in a strong heat for several hours, then. When cooled, add a small portion of concentrated marine acid, and suffer it to stand for an hour or two; then add water, and when the solution is clear, pour it off, and precipitate it by fixed alkali — 13! Grains of this precipitate, well washed and dried are equivalent to 100 of tin in its reguline state, i the precipitate consist of pure tin; but if it contair copper or iron, it must be calcined in a red heat for an hour, and then digested in nitrous acid, which will take up the copper; and afierwards in marine acid, which will separate the iron.