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.

    37/968 (page 19)
    I have already stated that the atomic weight of boracic acid “ass 1. is 8, and that it is a compound of Div. 1. 1 atom boron ; : 4 2 atoms oxygen : r 2 3 The scales obtained constitute a hydrated acid composed of 1 atom acid ’ , 3 2atoms water. Pe 4225 5:25 It is very sparingly soluble in water. Boiling water scarcely dissolves 0:02 of boracic acid, and cold water a still smaller quantity. When this solution is distilled in close vessels, part of the acid evaporates along with the water, and crystallizes in the receiver. Water, therefore, renders it in some measure volatile, though it is perfectly fixed when ina state of dryness. It is soluble in alcohol; and alcohol containing it burns with a green flame. Paper dipped into a solution of boracic acid burns with a green flame. With the assistance of a distilling heat, it dissolves in oils, especially in mineral oils; and with these it yields fluid and solid products, which give a green colour to spirit of wine. _ Boracie acid is an exceedingly feeble acid; so much so that it is capable of acting on very few of the metals. Indeed if we except iron and zine, there are none of these bodies which , it is capable of dissolving. It combines with bases in a great variety of proportions ; but no quantity of it whatever is capa- ble of depriving potash or soda of the property of giving a green colour to vegetable blues. The salts which it forms have received the name of borates. Their properties have not been much investigated. 2. Silicic Acid. Silica, or silicic acid, as it should be called, exists in greater abundance than any other, as it enters as a constituent into most of the rocks and stony bodies of which the earth is composed. There are no fewer than 167 species of minerals that contain silica as one of their essential constituents. Rock crystal, quartz, chalcedony, and flint consist of silica very nearly, but not quite in a state of purity. But from these bodies it is easy to obtain it quite pure by the following process: Put into a platinum Preparation. crucible equal weights of anhydrous carbonates of potash and