The discovery of oxygen, part 1 / Experiments by Joseph Priestley, LL.D. (1775).

  • Priestley, Joseph, 1733-1804.
Date:
1901
Catalogue details

Licence: In copyright

Credit: The discovery of oxygen, part 1 / Experiments by Joseph Priestley, LL.D. (1775). Source: Wellcome Collection.

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    three times its bulk of nitrous air. The last produce was very slow, and only about twice as good as common air. From an ounce-measure of ashes of pit-coal, burned with all possible care, and treated in the same manner as above, I got about three quarts of air, one-thiixl of which was fixed air, precipitating lime in lime-water; but the residuum was strongly nitrous, especially at the last. It is observable enough, from their dark colour (of which no burning, I believe, will divest them) that, in general, ashes of pit-coal contain much more phlogiston than ashes of wood. N.B. In this, and other processes, it will be observed, that fixed air was procured from substances, which can hardly be thought to have contained it before : which affords a presumption, that it is not an acid sui generis, but a modification of the nitrous acid. Clay is a substance altogether different from calcareous earth, and is not supposed, I believe, to contain any air at all. Of that species of it, which is called tobacco-pipe- clay, and which, I believe, is the purest of all, I got from Dr. Higgins, a quantity in powder; and moistening it with spirit of nitre, I observed that no more heat or effervescence was produced than the mixing of it with water would have occasioned. Putting it, when dry, into a gun-barrel, I extracted from it, by a strong heat, about two ounce-measures of air, which being pretty readily absorbed by water, neither affecting common air, nor being affected by nitrous air, and extinguishing a candle, I concluded to be fixed air. Repeating the experiment, I got the same produce, only observing, that the fixed air made lime- water turbid, the most certain test, I believe, of the presence of fixed air; and the last produce was highly nitrous. Imagining that this produce might have come from the phlogiston of the iron, I resolved to repeat the