No. 7.] WURTZ — THEORY OF ATOMS. 37^ 



nity of a system, which appeared solidly established during the 

 first half of this century. The facts then known were included 

 in it without difficulty, and the rich materials which the patience 

 or the genius of experimenters amassed without ceasing were 

 very soon co-ordinated. 



Without attempting to enumerate the older works relutiag to 

 the decomposition of alkalis, to the nature of chlorine recognised 

 as a simple body, to various newly-discovered elements, such as 

 selenium, tellurium, iodine, we shall mention in a special manner 

 among so many discoveries, that of cyanogen, which we owe to 

 our own Gay-Lussac. The demonstration of the chemical func- 

 tions of this compound gas, which behaves like a simple body, 

 which is capable of forming the most varied combinations with 

 true elements, which finally, when it is engaged in such combina- 

 tions lends itself to double decompositions, as does chlorine in 

 the chlorides, was a great step in the progressive march of science. 

 Hence the definition : cyanogen is a compound radical, and the 

 triumphant appearance of the doctrine of radicals. It had been 

 vaguely intimated by Lavoisier ; it really dates from the dis- 

 covery of cyanogen, and will make a rapid advance. Up to that 

 time great efforts had been directed to the side of inorganic 

 chemistry, and great ideas had arisen in this domain. The appli- 

 cation of these ideas to organic chemistry, upon which attention 

 then began to be directed, presented some difficulties. 



AYe know that the innumerable bodies which nature has dis- 

 tiibuted in the organs of plants and animals contain a small 

 number of elements— carbon, hydrogen, oxygen, and often nitro- 

 gen. It is then not in their general composition that they differ, 

 but by the number and arrangement of the atoms which enter 

 into their composition. By increasing more or less and grouping 

 themselves in various manners, these atoms give rise to an im- 

 inense multitude of distinct compounds which are true chemical 

 species. But what is the arrangement of these atoms? What 

 is the structure of these organic molecules, so much alike in the 

 nature of their elements, so wonderful in the iufiuite diversity of 

 their properties ? Berzelius solved this question without hesita- 

 tion. Comparing organic compounds to the bodies of inorganic 

 chemistry, he divided both classes of atoms into two lots, group- 

 ing on one side carbon and hydrogen, electropositives, and on the 

 other, oxygen, electro-negative. And when, at a later time, 

 chlorine was artificially introduced into organic compounds, the 



