Metallography as a separate science
(This historic book may have numerous typos and missing te...)
This historic book may have numerous typos and missing text. Purchasers can download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1871 Excerpt: ...aqueous ammonia into a solution of the sulphate in water; the precipitate which falls is to be washed, put into a mattress with potash-ley, and boiled for some time; it must then be filtered, washed, and dried. A brown powder is obtained, lighter than fulminating gold: this is fulminating platinum. When heated to 400 degs. it explodes, but does not detonate by friction or percussion. Notwithstanding all the valuable properties which this metal possesses, it is of little use to man, owing to its great scarcity, which has rendered it very expensive. Although it is some five times more costly than silver, it is of great value for chemical utensils, such as crucibles, spoons, small tongs, rods, &c., because it possesses the two-fold power of resisting high temperatures and chemical action. It is used also lor retorts for the concentration of sulphuric acid; and to make mirrors for reflecting telescopes. When beaten into thin leaves, it has sometimes been applied to porcelain in the same manner as leaf gold. A part of the Kussian coinage is cast in this metal. It is employed to obtain instantaneous light in Doebereiner's lamps, in the state of a fine powder called spongy platinum, which is procured by precipitating it in muriate of ammonia. CHAPTER XXXIX. POTASSIUM. Earlt in October, in the year 1807, Sir H. Davy succeeded in decomposing common potash, by the agency of voltaic electricity, and found that it consisted of oxygen and a peculiar metal which he named potassium, in the proportion, of 100 of potassium and 20 of oxygen. The metal has since been obtained in large quantities, simply by keeping potash in fusion with intensely hot iron. It is found in nature in great abundance, but only in combination, and generally as potash. Potash was formerly procur...
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