THE CHEMICAL ELEMENTS. 74.1 



nents is not the only cause of the differences which distinguish 

 compounds, but that the proportions in which these elements are 

 united, and perhaps also the mode of their union, are other causes 

 of these differences. 



" Thus the whole doctrine of the pretended elements, or of the 

 principles of things, or of their components, or of the compositions 

 of different orders of compounds, is now reduced to conceptions as 

 simple as they are precise. There are no hypotheses or useless 

 distinctions or erroneous abstractions in the present ideas of chem- 

 ists, and the obscurity which formerly reigned in this part of 

 the science has wholly disappeared, and at the same time we have 

 got rid of a source of vague and endless discussions. We have no 

 longer to dwell in the schools on useless questions about a primi- 

 tive matter and its relations ; on whether there are four, three, two, 

 or only a single element; on the pretended relations of the ele- 

 ments among themselves; on their transformation, or on the 

 change of one into another. All these dreams of a sham specula- 

 tive philosophy have vanished before the facts discovered by the 

 experimental method ; and the five propositions enunciated above, 

 as simple as they are true, are data on which we can now securely 

 build." 



Turning, now, to Lavoisier's own " Traits dMmentaire de 

 Chimie," which must be regarded as the " Principia " of chemical 

 science, we find, for the first time in the history of the subject, a 

 list of twenty-five definite substances distinguished as elementary 

 on the sole basis that they had as yet never been analyzed. This 

 list is given in the first column of the table which we reproduce 

 in translation on the following page, on account of its very great 

 historical interest. Still, there is even here an obvious survival of 

 Aristotle and the phlogiston theory, both in what the list includes 

 and in what it omits. The first name on the list is caloric, and 

 three of the other elements are the muriatic, fluoric, and boracic 

 radicals, which, though not yet isolated, appear to Lavoisier so 

 distinctly typified and foreshadowed that he does not hesitate to 

 name them in this list. These radicals, it must be noticed, were 

 radicals which, united to oxygen, would form respectively hydro- 

 chloric, hydrofluoric, and boracic acid, so that in the last case only 

 were Lavoisier's expectations realized in the form which he ex- 

 pected. Indeed, the radical of muriatic acid, chlorine, was then a 

 well-known substance, having been discovered by Scheele in 1774, 

 but so little did it answer to the expected radical that it was re- 

 garded by Lavoisier as an oxide, and named by him " acide muri- 

 atique oxygdn^," and under this name appears in this very table 

 (translated oxidized muriatic acid). What we know as chlorine 

 gas was classed by Lavoisier as the fourth degree of oxidation of 

 his assumed muriatic radical, while muriatic acid itself was the 



