Lavoisier on the Composition of Water, Oeuvres

Author: Antoine Laurent Lavoisier

The Permanence of Matter

Antoine Laurent Lavoisier

Engraving from an original by David

It results from the experiments described in chapters V and VI of the work which I published at the beginning of this year, under the title Opuscules Physiques et Chimiques, that when lead or tin is calcined in a retort (verre ardent) under a bell-glass plunged in water or in mercury, the volume of air is diminished about one-twentieth as a result of the calcination, while the weight of the metal is found to be increased by an amount approximately equal to that of the air destroyed or absorbed.

I felt justified in concluding from these experiments that a portion of the air itself, or of some substance contained in the air, and which exists there in an elastic state, combined with the metals during their calcination, and that the augmentation in weight of the metallic calxes was due to this cause.

The effervescence which constantly takes place in every revivification of metallic calxes, that is to say whenever a metallic substance passes from the condition of the calx (oxide) to that of the metal, came to the support of this theory. I think I have proved that this effervescence is due to the freeing of an elastic fluid, a kind of air (gas) which can be retained and measured, and the result of the many experiments to which I have subjected it is that when it had been separated from the metals by the addition of powdered charcoal, or any substance containing phlogiston, it did not differ in any respect from the substance to which I have given the name of fixed air, mephitic gas, mephitic acid, all synonymous terms, and that this gas was precisely the same whether disengaged from metallic calxes by means of powdered charcoal, from vegetable substances by fermentation, or from alkalies, saline or earthy, by their solution in acids.—Lavoisier on the Calcination of Tin, Oeuvres II, 105.

We began (our experiment) by testing what should be the opening of the stop-cocks to provide the due proportion of the two gases. This was easily ascertained by observing the color and brilliancy of the little tongues of flame which formed at the end of the tube, the right proportion of the two gases giving the most luminous and beautiful flame. This first point determined, we inserted the tube into the stem of the receiver, which was plunged into mercury, and allowed the gases to burn till we had used up all we had provided. From the first instant we saw the walls of the receiver becoming obscured and covered with vapor; soon this collected into drops and ran down upon the mercury from all sides, and in fifteen or twenty minutes its surface was completely covered. The difficulty was to collect this water, but that was easily accomplished by passing a plate under the receiver without taking that out of the mercury, and then pouring both the water and mercury into a glass funnel; finally letting the mercury run off, the water remained collected in the tube of the funnel; it weighed a little less than five drams (gross).

This water, subjected to every imaginable test, seemed as pure as distilled water; it did not redden at all the tincture of turnsol; nor turn green the syrup of violets; it did not precipitate lime-water; finally, one could not by any known reagents discover in it the slightest trace of admixture.

As the two airs [gases] were conducted from pneumatic receptacles (caisses) to the receiver through flexible leather pipes, and these were not absolutely impermeable to the air (gas) it was not possible for us to be certain as to the exact quantity of the two gases whose combustion we had thus brought about; but as it is not less true in physics than in geometry that the whole is equal to its parts, and as we had obtained by this experiment only pure water, without any other residue, we thought ourselves justified in concluding that the weight of this water was equal to that of the two gases which had served to produce it. But one reasonable objection could be brought against this conclusion: admitting that the water produced was equal in weight to the two gases, was to suppose that the matter of the heat and light so abundantly set free in this operation, and which passes through the pores of the vessels, had no weight; which assumption might be regarded .as gratuitous. I found myself, therefore, confronted with this important question: whether the matter of heat and light has any sensible and appreciable weight in physical experiments, and I decided in the negative on the strength of facts which seemed to me conclusive and which I have set forth in a memoir deposited some months ago with the secretary of the Academy.—Lavoisier on the Composition of Water, Oeuvres II., 338, 339.

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Chicago: Antoine Laurent Lavoisier, Lavoisier on the Composition of Water, Oeuvres in The Library of Original Sources, ed. Oliver J. Thatcher (Milwaukee, WI: University Research Extension Co., 1907), 298–299. Original Sources, accessed July 1, 2022,

MLA: Lavoisier, Antoine Laurent. Lavoisier on the Composition of Water, Oeuvres, in The Library of Original Sources, edited by Oliver J. Thatcher, Vol. 6, Milwaukee, WI, University Research Extension Co., 1907, pp. 298–299. Original Sources. 1 Jul. 2022.

Harvard: Lavoisier, AL, Lavoisier on the Composition of Water, Oeuvres. cited in 1907, The Library of Original Sources, ed. , University Research Extension Co., Milwaukee, WI, pp.298–299. Original Sources, retrieved 1 July 2022, from