Of great importance is the chemical identity of the diamond, graphite and charcoal, a fact demonstrated in part by Lavoisier in 1773, Smithson Tennant in 1796, and by Sir George Steuart-Mackenzie (1780-1848), who showed that equal weights.
Their quantitative experiments were, however, too rough to permit of accurate generalization; and although Lavoisier and Laplace stated the principle that the same amount of heat must be supplied to decompose a compound as would be produced on its formation, the statement was not based on exact experiment, and only received experimental confirmation much later.
Berzelius, in 1813 and 1814, by improved methods of analysis, established that the Daltonian laws of combination held in both the inorganic and organic kingdoms; and he adopted the view of Lavoisier that organic compounds were oxides of compound radicals, and therefore necessarily contained at least three elements - carbon, hydrogen and oxygen.
He published Entwicklungsgeschichte der Chemie von Lavoisier bis zur Gegenwart (1868) and other works on chemistry, collaborated in a Handworterbuch der Chemie (13 vols., 1882-96), and wrote a volume of reminiscences, Lebenserinnerungen (1912).
The theory advocated by Lavoisier came to displace the phlogistic conception; but at first its acceptance was slow.
Darwin's work shows, however, the tendency to connect medicine with physical science, which was an immediate consequence of the scientific discoveries of the end of the 18th century, when Priestley and Cavendish in England exercised the same influence as Lavoisier in France.
A petition in his favour addressed to Coffinhal, the president of the tribunal, is said to have been met with the reply La Republique n'a pas besoin de savants, and on the 8th of the month Lavoisier and his companions were guillotined at the Place de la Revolution.
In effect, therefore, Mayow - who also gives a remarkably correct anatomical description of the mechanism of respiration - preceded Priestley and Lavoisier by a century in recognizing the existence of oxygen, under the guise of his spiritus nitro-aereus, as a separate entity distinct from the general mass of the air; he perceived the part it plays in combustion and in increasing the weight of the calces of metals as compared with metals themselves; and, rejecting the common notions of his time that the use of breathing is to cool the heart, or assist the passage of the blood from the right to the left side of the heart, or merely to agitate it, he saw in inspiration a mechanism for introducing oxygen into the body, where it is consumed for the production of heat and muscular activity, and even vaguely conceived of expiration as an excretory process.
Taking magnesia alba, which he distinguished from limestone with which it had previously been confused, he showed that on being heated it lost weight owing to the escape of this fixed air (named carbonic acid by Lavoisier in 1781), and that the weight was regained when the calcined product was made to reabsorb the fixed air with which it had parted.
Cavendish, Priestley, Lavoisier and others contributed to this result.