Volume 2

A system of chemistry of inorganic bodies / By Thomas Thomson.

  • Thomson, Thomas, 1773-1852.
Date:
1831
Catalogue details

Licence: Public Domain Mark

Credit: A system of chemistry of inorganic bodies / By Thomas Thomson. Source: Wellcome Collection.

    36/968 (page 18)
    Chap, L Properties, SECTION V.—ACIDS OF BORON AND SILICON. The acids formed by the combination of these two bases with oxygen, are two in number. They are both feeble acids, and capable of combining with bases in various proportions. 1. Boracie Acid. This acid united to soda occurs in China and Thibet. It occurs in a free state, and seemingly in great abundance in several lakes in Tuscany. Great quantities of this native acid have for some time been imported into this country, where it is converted into borax for the use of the potters, who have been long in the habit of using it as a glaze for the finer kinds of stone-ware. The most considerable of the Tuscan lakes which yield this acid is the Cerchiajo, on the Monte rotondo. Though it is only about 60 feet long and 42 feet broad, the soil in the neighbourhood becomes covered with an efflorescence consisting chiefly of boracic acid, but mixed with sal ammoniac, and some other saline matters. Boracic acid is usually prepared from borax. Four parts of this salt are dissolved in boiling water, and one part of concen- trated sulphuric acid is added to the solution. The boracic acid is deposited in crystalline scales as the liquid cools. These scales are to be collected, dried, and then exposed to a red heat in a platinum crucible to drive off a portion of sulphuric acid, which cannot be separated by washing. It may then be dis- solved in boiling water and crystallized anew. Boracic acid, thus procured, is in the form of thin hexagonal scales, of a silvery whiteness, having some resemblance to sper- maceti, and the same kind of greasy feel. H has a bitterish cooling taste, and at last leaves an agreeable sweetness. It has no smell; but when sulphuric acid is poured on it, a tran- sient odour of musk is produced.* : | It reddens vegetable blues feebly. And Mr. Faraday has likewise remarked that it reddens turmeric paper. Its specific as high as 1-830. . It is not altered by light. It is fixed in the fire. Ata red heat it melts, and is converted into a hard transparent glass ; which becomes somewhat opaque when exposed to the air, but does not attract moisture. * Reuss, de Sale Sedat. 1778, + Kirwan’s Mineralogy, ii. 4. T Roget and Dumas, Annals of Philosophy (2d series), iii. 392.