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Ivory has the same chemical constitution as ordinary teeth that is, cartilage united to such earthy ingredients as the phosphate of lime. But it is very remarkable that the fossil ivory of the mammoth, and specimens of the historic period of Pompeii or Egypt, contain sometimes as much as 10 per cent. more of fluoride of calcium than the ivory of the present day.
An English chemist reports that the South Carolina phosphate, made in factories situated in and near Charleston, ranks next in value to this Cambridge product. It contains 54 per cent. of tribasic phosphate of lime, 14 per cent. of carbonate of lime, 3-1/2 per cent. of iron oxide and alumina, 2-1/2 per cent. of fluoride of calcium, and 15 per cent. of silica.
We apprehend, however, that this property first investigated by Dr George Wilson may be derived from long-continued contact with earth, since fluoride of calcium is the chief ingredient in the enamel or exterior portion of the tooth. Ancient ivory, having thus gained in its inorganic bases, becomes deficient in the gelatinous constituents necessary to its preservation.
Filter, wash, ignite, and weigh. The reaction involved is: BaSO + Na CO , > BaCO , + Na SO . As the sodium sulphate is soluble in water, and the barium carbonate insoluble, a separation between them is possible and the sulphur can be determined in the water-soluble portion. The mineral apatite is composed of calcium phosphate, associated with calcium chloride, or fluoride.
While the arcs with plain carbons are bluish-white, those with carbons containing calcium fluoride have a notable golden glow.
The air was faintly yellow, the sky was yellow with a greenish cast, and the clouds were green-gray. No human had ever set foot on the surface, or breathed the air, of Niflheim. To have done so would have been instant death; the air was a mixture of free fluorine and fluoride gasses, the soil was metallic fluorides, damp with acid rains, and the river was pure hydrofluoric acid.
It is tested by volatilisation of the silica as silicon fluoride after solution in hydrofluoric acid, and, if the analysis has been properly conducted, the residue, after treatment with the acids and ignition, should not exceed 1 mg.
Aluminium, the now well-known valuable metal, present in clay, bauxite, and a variety of other mineral substances, is electrolytically deposited from a bath of alumina obtained by dissolving bauxite either in potassium fluoride or in cryolite. Aluminium is now coming into extended use in the construction of long-distance electric power transmission lines.
These include the fluoride of calcium, of which the most familiar variety to Englishmen is that known as Derbyshire spar, of which many useful articles are manufactured in this country. Ladies particularly will halt with interest before the case marked 58 A, where the fluorides, better known as the topaz, are deposited. These include a fine series of crystals from the Brazils, Siberia, and Saxony.
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