This last statement explains the name which he gave to Priestley's and Scheele's gas, namely oxygen, a word derived from two Greek words, signifying " acid-producer." The compounds of this substance he termed "oxides;" and it is to him that we owe the system of nomenclature now generally in use. Before the end of the century, the doctrines of Lavoisier had gained almost universal acceptance.

The word "analysis," as has been stated, was suggested by Boyle, to signify the ascertaining the composition of substances. Attempts were made by him, and by other chemists, especially by Black, to perform quantitative analyses during the seventeenth and the first half of the eighteenth centuries. Priestley and Scheele tried to find the relative proportions of oxygen in air with partial success ; but it was not until Lavoisier had convinced most chemists that oxygen was a substance, and not the negation of one, like the absence of phlogiston, that serious attention was directed to accurate determinations of quantity. And towards the end of the eighteenth century fairly trustworthy data began to accumulate.