The discovery of oxygen.

  • Scheele, Carl Wilhelm, 1742-1786.
Date:
1894
Catalogue details

Licence: Public Domain Mark

Credit: The discovery of oxygen. Source: Wellcome Collection.

Provider: This material has been provided by UCL Library Services. The original may be consulted at UCL (University College London)

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    and colourless like water. This acid has all the chief properties of acid of nitre, except that the yellow colour is wanting. This I call the pure acid of nitre; as soon, however, as it comes into contact with an inflammable substance, it becomes more or less red. This red acid is more volatile than the pure, hence heat alone can separate them from one another; and, for exactly the same reason, the volatile spirit must go over first in the distillation of Glauber's spirit of nitre. When this has gone over, the colourless acid follows ; but why does the acid make its appearance again so blood-red at the end of the distillation ? Why has not this redness already been driven over at the beginning ? Where does it now obtain its phlogiston? This is the difficulty. 26. I intimated in the preceding paragraph that the candle went out in the receiver at the beginning of the distillation. The reason is to be found in the experiment which I have cited in § 13. In this case the acid of nitre, passing over in vapours, takes to itself the inflam- mable substance, whose presence is indicated by the black colour of the oil of vitriol; as soon as this has taken place it meets with the air, which again robs the now phlogisticated acid of its inflammable substance ; by this means a part of the air contained in the receiver becomes lost, hence the fire introduced into it must go out (§ 15). 27- The acid of nitre can attract phlogiston in varying quantity, when it likewise receives other properties with each proportion. (a.) When it becomes, as it were, saturated with it, a true fire arises, and it is then com- pletely destroyed, (b.) When the inflammable principle is present in smaller quantity, this acid is converted into a kind of air which will not unite either with the alkalies or with the absorbent earths, and with water only in very small quantity. When this acid of nitre, resembling air,