The famous 'Greek fire', which played so important a part in the defense of the Byzantine empire from the seventh century, had no precise formula, but its essential ingredient seems to have been naphtha... It appears that by the eleventh century the Chinese were aware that the incendiary properties of such mixtures could be much increased by the addition of nitre, the reason being that when it is heated this substance yields oxygen.
He was acquainted with nitric acid which he obtained by distilling a mixture of saltpetre and green vitriol. He mentions its power of dissolving, not merely mercury, but likewise other metals. He could form aqua regia by adding sal ammoniac or common salt to nitric acid, and he was aware of the property which it had of dissolving gold.
During the year 1796 he made his experiments to prove that the diamond is pure carbon. His method was to heat it in a gold tube with saltpetre. The diamond was converted into carbonic acid gas, which combined with the potash from the saltpetre, and by the evolution of which the quantity of carbon, in a given weight of diamond, might be estimated.