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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    exposed to the same degree of heat. The former yielded twenty two ounce-measures of air, after the fixed air was pretty well washed out of it. It was about five times as good as common air. The latter had lost nineteen grains in weight, being just so much less than half an ounce ; so that the twenty-two ounce-measures of air should have weighed nineteen grains, which is certainly a great deal too much: besides, in this experiment, as in the former, no account could be taken of the fixed air. Finding these methods to fail, I had recourse to that which was used by Mr. Cavendish in weighing fixed and inflammable air, and which is more accurate than the method which I had used before (viz. filling a Florence- flask with the different kinds of air, and weighing them in it) because, as the flask must be first filled with water, one cannot be sure, though every possible precaution be taken, that the water has been equally drained from it after each experiment : otherwise there would be a con- siderable advantage in this method ; because the quantity of air may be accurately known. But though this can- not be done with precision in a bladder, as used by Mr. Cavendish, because the degree of distension cannot be measured with much accuracy, yet this circumstance is more than counterbalanced by being able to change the air with compressing the bladder, without wetting it. I therefore took a glass-tube about nine inches long, and fastening it to the neck of a bladdei, which, with such a degree of distension as I could give it, in the manner in which the experiment was made, contained fifty-five ounce-measures, or one pennyweight nine grains of common air. The tube was so fastened, that I could take it out at pleasure ; and having the bladder thus prepared, I carefully compressed it, then filling it in part with that kind of air which I was about to weigh, I com pressed it again, and then filled it intirely ; so that I was