Volume 2

The elements of experimental chemistry / [William Henry].

  • Henry, William, 1774-1836
Date:
1818
Catalogue details

Licence: Public Domain Mark

Credit: The elements of experimental chemistry / [William Henry]. Source: Wellcome Collection.

    43/636 (page 23)
    ;J analysis, has at length yielded to the attempts of Sir H. Davy to decompose it by the action of Voltaic electricity. When | slightly moistened with water, and exposed, between two sur¬ faces of platina, to a battery of 500 pairs of plates, an olive- brown matter immediately began to form on the negative sur- face, which gradually increased in thickness, and at length be¬ came almost black. It was not changed by water, but dis¬ solved with effervescence in warm nitrous acid. When heated to redness on platina, it burned slowly, and gave off white fumes, which had acid properties. A black mass remained, which, when examined by the magnifier, appeared vitreous at ! the surface, and evidently contained a fixed acid. Boron. As this peculiar combustible substance is a non-conductor of electricity, it was found impossible to obtain it in this way, except in very thin films. By the action of potassium, how- i ever, it was procured in larger quantities. Twelve or fourteen ; grains of boracic acid were heated, in a green glass tube, with the same quantity of potassium. A most intense ignition en¬ sued ; and the potassium, where it was in contact with the boracic acid, entered into vivid imflammation. A quantity of hydrogen gas appeared, equal to about twice the bulk of the acid. To collect the results, tubes of metal were employed; for the most part of brass, which appears to answer best. The residue in the tube was dissolved in water, and the in¬ soluble part collected on a filter. Its properties are described as follows: 1. It is in the form of a powder, in colour of the darkest shade of olive. It is very friable, and not sufficiently hard to scratch .glass. It is a non-conductor of electricity. 2. When it has been dried at only 100° or 120°, it gives off moisture by increase of temperature. In the atmosphere it takes fire, at a heat below that of boiling olive oil; and burns with a red light, and scintillations like charcoal. 3. It is not decomposed by heat in a platina tube, though raised to whiteness. The only change in it appears to be an increase of specific gravity. 4. In oxygen gas it burns with a most brilliant light, and is