100 BIOGRAPHIES OF SCIENTIFIC MEN 



why he had abandoned organic chemistry, replied that 

 " now, with the theory of substitution as a foundation, 

 the edifice may be built up by workmen : masters are 

 no longer needed." 



Although he had his own views on most subjects, he 

 was always open to correction. He said : "In the history 

 of the evolution of any science, the researches of a given 

 period of time furnish certain general relations which 

 every moment are changed and improved upon by new 

 discoveries. Thus an endeavour arises to arrange the 

 new-discovered facts and to find the common bond by 

 which they are linked together." 



Liebig's definition of a compound radicle holds good 

 to this day, although his definition of organic chemistry 

 as the study of the compound radicles has been super- 

 seded by that of Schorlemmer, who defines organic 

 chemistry as that branch of the science which treats of 

 " the hydrocarbons and their derivatives." 



Liebig predicted the organic ammonias, and discovered 

 chloroform the invaluable liquid which was first intro- 

 duced into medicine by Sir James Simpson in 1848. He 

 also discovered chloral and aldehyde. Liebig established 

 the molecular formula of citric acid, and proved that it 

 was tribasic; and in the year 1838 appeared his classical 

 memoir on the constitution of organic acids, showing 

 that the doctrine of basicity could be applied to them as 

 well as to the acids of inorganic chemistry. 



