CHEMISTRY OF THE EIGHTEENTH CENTURY. 367 



Lavoisier burnt a weighed quantity of phosphorus in a known 

 quantity of oxygen gas. The combustion was very rapid, and accom- 

 panied by an extremely brilliant light and much heat ; and as it went 

 on, large quantities of white flakes were formed in the vessel. This 

 white matter was collected and weighed, and its weight was found to 

 be exactly the sum of the weights of the phosphorus and of the oxygen 

 which had disappeared. The white substance is very soluble in water 

 and intensely sour, properties which are absent from the phosphorus. 

 Sulphur burnt in oxygen also produces an acid, and charcoal unites 

 with oxygen, forming " fixed air," to which Lavoisier first gave the 

 name of carbonic acid gas. The gaseous acid produced by the com- 

 bustion of sulphur had long been known under the name of sulphurous 

 acid, and Lavoisier found that sulphur combined with a greater propor- 

 tion of oxygen than existed in the gaseous acid, constituted the vitriolic 

 acid. But Lavoisier and certain other French chemists remodelled 

 entirely the system of naming chemical compounds, by adopting the 

 intelligible principle that the name should express the composition of 

 the substance. In such cases as that of the two acids of sulphur, it 

 was agreed that the compound containing the less proportion of oxygen 

 should be termed sulphur^^ acid ; while the other, having the higher 

 proportion of oxygen, should be distinguished as sulphur/*; acid. Before 

 the great reform of chemical nomenclature introduced by Lavoisier 

 and Morveau, substances often received names according to the source 

 from which they were obtained, or sometimes according to the dictates 

 of caprice and suggestions of fanciful analogies. The acid obtained 

 from green vitriol (sulphate of iron) was called vitriolic acid ; that pro- 

 duced by burning sulphur was called sulphurous acid ; but it was not 

 until the disc6veries of Lavoisier that the connection of these sub- 

 stances was recognized and expressed by the names he gave them. 



There was one well-known acid, however, which Lavoisier was 

 unable to bring under his rules of naming, for its true composition 

 was unknown at the time. When common salt is heated with sul- 

 phuric acid, a strong volatile acid distils over, to which it had been 

 usual to give the name of "spirit of salt." Lavoisier acknowledges 

 that he is unable to discover the base of this acid, but he is firmly 

 convinced that it consists of some substance united to oxygen, and, 

 although unknown, he calls this substance the muriatic base, or muri- 

 atic radical, from the Latin word muria which was anciently used to 

 signify sea-salt, while the acid itself he termed muriatic acid. This 

 name became established, and remained in use even after the real 

 nature of the acid was ascertained to be very different from that which 

 Lavoisier attributed to it. It will be remembered that Scheele had 

 discovered the gas we now call chlorine by heating muriatic acid and 

 black oxide of manganese. The nature of the action which took place 

 was long misunderstood. It was supposed that the muriatic acid 

 derived oxygen from the oxide of manganese, and hence chlorine was 



