In 1775 Lavoisier's paper, "On the Nature of the Principle which combines with the Metals during their Calcination, and which augments their Weight," was read before the Academy. The preparation and properties of an air obtained, in November 1774, from _red precipitate_ are described, but Priestley's name is not mentioned. It seems probable, however, that Lavoisier learned the existence and the mode of preparation of this air from Priestley;[5] but we have seen that even in 1779 Priestley was quite in the dark as to the true nature of the air discovered by him (p. 60). In papers published in the next three or four years Lavoisier gradually defined and more thoroughly explained the phenomenon of combustion. He burned phosphorus in a confined volume of air, and found that about one-fourth of the air disappeared, that the residual portion of air was unable to support combustion or to sustain animal life, that the phosphorus was converted into a white substance deposited on the sides of the vessel in which the experiment was performed, and that for each grain of phosphorus used about two and a half grains of this white solid were obtained. He further described the properties of the substance produced by burning phosphorus, gave it the name of _phosphoric acid_, and described some of the substances formed by combining it with various bases. The burning of candles in air was about this time studied by Lavoisier. He regarded his experiments as proving that the air which remained after burning a candle, and in which animal life could not be sustained, was really present before the burning; that common air consisted of about one-fourth part of dephlogisticated air and three-fourths of _azotic air_ (_i.e._ air incapable of sustaining life); and that the burning candle simply combined with, and so removed the former of these, and at the same time produced more or less fixed air.