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The pink topaz is made from the yellow, which, when of intense colour, is put into the bowl of a tobacco pipe, or small crucible, covered with ashes or sand: on the application of a low degree of heat, it changes its colour from a yellow to a beautiful pink. It contains fluoric acid, which may be the means of this change. Mawe. Why is ruby of such a brilliant colour?
Baron Japhet applied the nervous fibres of his tongue to the skin; he had skill in thus detecting salts, acids, alkalis, and gases. After several experiments, he remarked: "No taste whatever! Come, we will give it a little fluoric acid to drink." Subjected to the influence of this ready solvent of animal tissue, the skin underwent no change whatsoever.
It was also found by analysis that augite usually contained more lime, less alumina, and no fluoric acid; which last, though not always found in hornblende, often enters into its composition in minute quantity. In addition to these characters, it was remarked as a geological fact, that augite and hornblende are very rarely associated together in the same rock.
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