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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    fuming acid of nitre from oil of vitriol and nitre, when it is impossible that they should not have observed how this acid went over red in the beginning, white and colourless in the middle of the distillation, but at the end red again; and indeed so dark-red that one could not see through the receiver? It is to be noticed here that if the heat is permitted to increase too much at the end of the distillation, the whole mixture enters into such frothing that everything goes over into the receiver; and, what is of the greatest importance, a kind of air goes over during this frothing which deserves no small atten- tion. If one takes for such distillation a very black oil of vi.triol, not only does the acid go over at the beginning of a far darker red than when one takes a white oil of vitriol, but further, when one introduces a burning candle into the receiver after about an ounce has gone over, this goes out immediately. On the other hand, when one places a burning candle in the receiver filled with blood-red vapours, towards the end of the distillation when, as has been said, the mixture froths strongly, not only will it continue to burn, but this will take place with a much brighter light than in ordinary air. The same thing occurs when one attaches, at the close of the distil- lation, a receiver which is filled with an air in which fire will not burn, for, when this has been attached for half an hour, a candle will likewise continue to burn in the air. In this case there now arises in the first place the question : Are the vapours of the acid of nitre naturally red? I beg leave to raise this question here because I believe there are people who advance the redness of this acid as a distinguishing characteristic. The colours of the acid of nitre are accidental. When a few ounces of fuming acid of nitre are distilled by a very gentle heat, the yellow separates itself from it and goes into the receiver, and the residuum in the retort becomes white