Volume 1

A manual of chemistry / by William Thomas Brande.

  • William Thomas Brande
Date:
1848
Catalogue details

Licence: Public Domain Mark

Credit: A manual of chemistry / by William Thomas Brande. Source: Wellcome Collection.

Provider: This material has been provided by King’s College London. The original may be consulted at King’s College London.

    1255/1276 (page 1125)
    to condense the vapor, and the carbonic oxide produced during the opera- tion should be allowed to escape through a long tube drawn out into a small opening, and inserted into the tubulure. The product obtained is bromide of silicium mixed with bromine; the latter may be abstracted by agitation in a retort with mercury, and the former distilled off.’ (Serullas, Ann. Ch. el PJi., viii. 1; Phil. Mag. and Ann., xi. 395.) Fluoride op Silicium. Fluosilicic Acid. Silicated Fluoric Acid. SiF2. The only acid body which acts energetically upon silica is the hydrofluoric acid: the result of this action is a gaseous compound. To obtain it, 4 parts of pulverized fluor spar and 3 of powdered glass, or 2 of silica finely powdered, are well mixed in a retort with about 5 parts of oil of vitriol; the gas evolved is to be collected over mercury, and when its production slackens, it may be accelerated by a gentle heat. The mercury and the glass vessels employed must be quite dry, for if in the least damp, they acquire an immovable film of silica. This decompo- sition depends upon the evolution of hydrofluoric acid and its action upon the silica, water and fluoride of silicium being the ultimate results. Si02 + 2HF — SiF2 + 2HO. The hydrofluoric acid is derived from the action of the aqueous sulphuric acid on the fluoride of calcium; CaF + S03,H0 = HF + Ca0,S03. These changes are further shown in the following diagrams:— Hydrofluoric Acid 20 Fluoride of Calcium 39 Lime , Sulphuric 2ft “1 Acid, 40 Sulphate of Lime 63 Fluorine , Hydrogen 19 ' 1 Calcium , Oxygen Water . 9 20 + 8 Aqueous Sulphuric Acid 40 Water 18 Hydro- fluoric Acid 40 Hydrogen , Oxygen 2 “*■ 16 Silica 31 Fluorine , Silicium 38 -T 15 Fluoride of Silicium 53 Fluoride of silicium is a colorless gas; its odor is acrid, somewhat resembling that of hydrochloric acid; its taste very sour; its specific gra- vity is 3'6 compared with air: 100 cubic inches weigh nearly 112 grains. It extinguishes the flame of a taper. It produces white fumes when in contact with damp air, and when exposed to water it is absorbed, and a soluble compound of silica with hydrofluoric acid is formed, whilst ’a quantity of silica is at the same time precipitated. According to Berze- lius, one-third of the silica of the gas is deposited in the state of gelati- nous hydrate, and the compound retained in solution consists of 2 atoms of silica and 3 of hydrofluoric acid; the action, therefore, of 3 atoms of fluoride of silicium upon fi of water may be represented thus. 3SiF2 + 6110 = Si02+2[Si02,3HF]. If the beak of the retort from which the gas is issuing be plunged into a basin of water, it is soon choked by the copious deposit of hydrated silica, which sometimes forms tubes through the water, by which the gas escapes directly into the air. When it is intended to saturate water with the gas (it takes up about 2(50 volumes), this effect may be prevented by agitation, or better by suffering the gas to 4 1) 2