122 HISTORY OF CHEMISTRY. [LECTURE VII. 



acid, C 4 H 6 , of benzoic acid, C 14 H 10 , etc., spoken of, and these 

 radicals are the remainders of .the acids after the deduction of 

 their oxygen. 



It is easily understood that endeavours should be made 

 from other points of view, and in other directions, to establish 

 hypotheses regarding the nature of organic substances ; but I 

 may pass over those which possessed no general significance 

 and were applicable to a few substances only. I must, however, 

 adduce one example of this kind, because the idea involved was 

 for a long time held in respect in chemistry. It has to do with 

 a conception of oxalic acid, which was then written C 2 O :1 , the 

 elements of water being neglected. Dobereiner, who carefully 

 studied the behaviour of the oxalates in 1816, proved that some 

 of them give off carbonic anhydride and carbonic oxide when 

 heated, and on this account he thought himself justified in 

 regarding the " acid of sorrel " as carbonate of carbonic oxide. 41 

 This was an attempt to refer back complex substances to 

 simpler ones, and it possesses a certain significance, in so far 

 that it is based upon facts. 



More important by far is an observation of Gay-Lussac's 

 concerning the composition of alcohol and of ether, which dates 

 from about the same time, 42 and which became the basis of the 

 so-called Etherin Theory. The discoverer of the law of gaseous 

 volumes points out that the densities of the vapours of alcohol, 

 ether, and water, and the density of olefiant gas, stand to each 

 other in such a relation that ether may be regarded as com- 

 posed of half a volume of water vapour and one volume of 

 olefiant gas, and alcohol as composed of equal volumes of 

 the two. 



Dumas and Boullay adopted this observation as the basis 

 of the views regarding the ethereal compounds, which they 

 advanced in 1828 on the occasion of a detailed investigation 

 of these substances. 43 In their view olefiant gas is a radical ; 

 that is, a group of atoms which enters into combinations in 



41 Schweigger's Journal. 16, 105. 42 Ann. Chim. 91, 160 ; 95, 311. 

 * Ibid. [2] 37, 15." 



