LECTURE VII.] HISTORY OF CHEMISTRY. 125 



element." 49 As a consequence of Gay-Lussac's investigation, 

 and of the isolation of cyanogen, this latter view had acquired 

 an increased significance. Reflections of a similar kind do not 

 appear to have occurred further to the chemists of that period. 

 Generally speaking, radicals were only looked for in oxygen 

 compounds, and especially in acids ; whereas Dumas' and 

 Boullay's assumption of Etherin proves, on the other hand, 

 that attention was not confined exclusively to these. 



Wohler and Liebig's investigation of bitter almond oil and 

 its derivatives, in i832, 50 had a pronounced effect on the views 

 respecting radicals. It led these two chemists to the assump- 

 tion of a radical containing oxygen, and thus added an entirely 

 new significance to these ideas. 



Wohler and Liebig first show that the conversion of bitter 

 almond oil into benzoic acid consists in the taking up of oxygen, 

 since they establish the formulae C 14 H 12 O 2 and C 14 H 12 O 4 respec- 

 tively for the two substances. 51 In doing so, they assume, 

 however, an atom of water, H 2 O, in the latter; but they 

 neglect this and write the formula of benzoic acid C 14 H 10 O 3 . 

 In this way they come to look upon both substances as com- 

 pounds of the radical Benzoyl, C J4 Hi O 2 , and to regard bitter 

 almond oil as benzoyl hydride, and benzoic acid as an oxygen 

 compound of the new radical. They show, in the course of 

 the investigation, how the same radical may likewise be 

 assumed in an extensive series of substances. By treatment 

 of bitter almond oil with chlorine and bromine, they prepare 

 benzoyl chloride and bromide, C 14 H 10 O 2 .C1. and C 14 H 10 O 2 .Br 2 . 

 From these, by means of potassium iodide and of potassium 

 cyanide, they obtain the iodine and the cyanogen compounds 

 of the radical, C 14 H 10 O 2 .I 2 and C 14 H 10 O 2 .Cy 2 . Finally, with 

 ammonia and with alcohol, they obtain benzamid and benzoic 

 ether. 



This investigation is regarded even now as one of the 

 greatest achievements in the range of organic chemistry. The 



49 Lavoisier, Oeuvres. I, 138. 50 Annalen. 3, 249. 51 Berzelius' 

 atomic weights. 



