Experiments upon magnesia alba, quick-lime, and other alcaline substances / by Joseph Black.

  • Black Joseph, 1728-1799.
Date:
1893
Catalogue details

Licence: Public Domain Mark

Credit: Experiments upon magnesia alba, quick-lime, and other alcaline substances / by Joseph Black. Source: Wellcome Collection.

Provider: This material has been provided by the Royal College of Physicians of Edinburgh. The original may be consulted at the Royal College of Physicians of Edinburgh.

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    distillation. The acid remained in the retort : and he found, in the receiver, eight ounces of an alkahne spirit, which, he tells us, was extremely volatile, very much resembling the spirit of salt-ammoniac distilled with quick-lime; and no crystals were formed in it, when exposed to the cold air. A caustic volatile alkali may also be obtained, by mixing salt-ammoniac with half its weight of a caustic fixed alkali, or of magnesia which has been previously deprived of its air by fire; and then submitting these mixtures to distillation: Or, merely by adding any ordinary volatile alkali to a proper quantity of a caustic-ley; for, in this case, the air passes from the volatile to the fixed alkali, by a superior attraction for the last; and, by a gentle heat, the compound yields a spirit similar to that prepared from salt-ammoniac and quick-lime, It is therefore probable, that, had we also a method of separating the fixed alkali from an acid, without at the same time saturating it with air, we should then obtain it in a caustic form ; but I am not acquainted with an instance of this separation in chemistry. There are two, indeed, which at first sight appear to be of this kind: these are the separation of the fixed alkali from the nitrous acid, by means of inflamed charcoal, in the process for making nitnim fixatuni; and of the same alkali, from vegetable acids, merely by heat. But, upon examining the product of each process, we find the alkali either fully or nearly saturated with air. In the first, either the charcoal or the acid, or both together, are almost wholly converted into air; a part of which is probably joined to the alkali. In the second, the acid is not properly separated, but rather destroyed by the fire ; a considerable portion of it is converted into an inflamm- able substance: and we learn from Dr Hales that the bodies of this class contain a large quantity of fixed air.