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

  • Priestley, Joseph, 1733-1804.
Date:
1901
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Licence: In copyright

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

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    But I suspect that there is a farther difference in the mode in which phlogiston is combined with spirit of nitre, in the constitution of nitrous air. In this experiment, the dephlogisticated air was so pure, that one measure of it, and two of nitrous air, occupied the space of £ of a measure. Had the air been more pure, it would, no doubt, have been speci- fically heavier still. It should be observed, that sufficient time ought to be allowed to get dephlogisticated air intirely free from fixed air before it is weighed; and as this requires time, and perhaps may never be done completely, it may be suspected that the additional weight of this kind of air is owing to a mixture of fixed air. But common air also contains a great proportion of fixed air, and the dephlo- gisticated air, on which I made this experiment, had been produced, at least the far greatest part of it, and had been exposed to water, some weeks. It is, however, sufficiently evident, that dephlogisticated air doth become better by standing in water; owing, probably, to its depositing more fixed air in those circumstances. Having at one time made a large reservoir of dephlo- gisticated air, for the purpose of experiments, I found that, in about ten days, from being 4J, it had become 5 A better than common air. Standing in pure water must be a surer method of getting the purest dephlogisticated air, than agitation in water ; for, though the latter method will enable the water to absorb the fixed air faster, and therefore a little agitation at the first will be very useful, in order to expedite the purification of it; yet, as I have found (vol. I. p. 158) that agitation in the purest water will, in time, injure common air; the same operation may be supposed to injure dephlogisticated air also ; and indeed I have already observed, that having agitated in water a quantity of dephlogisticated air, a candle burned