100 PROGRESS OF SCIENCE IN THE CENTURY. 



indeed be noted that he did not build up urea from 

 its elements, but started with cyanic acid, which 

 would now be classed as an organic compound. 



Professor Meldola has called attention * to the his- 

 torical fact that Henry Hennell deserves a place 

 among the pioneers of chemical synthesis, for in 

 1826-1828 he effected the synthesis of alcohol from 

 ethylene. 



Though neither synthesis was complete, the steps 

 were very important. They indicated the beginning 

 of the end of vital force as a chemical factor, the 

 beginning, too, of a remarkable series of synthetic 

 achievements, — trichloracetic acid (Kolbe), formic 

 acid and alcohol (Berthelot), indigo, grape-sugar, 

 and many more — about 180 in all — all of which have 

 been artificially produced. 



Isomerism. — Wohler's synthesis of urea did not 

 quickly find the recognition it deserved, but it doubt- 

 less helped to break down the arbitrary distinction 

 between inorganic and organic chemistry, and to 

 further the progress of the latter, which began to be 

 spoken of as the chemistry of the carbon compounds. 

 But Wohler was also concerned in other steps hardly 

 less significant. 



The first of these steps is indicated by the word 

 isomerism. Even Dalton had called attention to the 

 existence of substances of identical chemical com- 

 position, but with different properties, and had sug- 

 gested that this might be explained by different or 

 multiple arrangement of the constituent atoms. But 

 little notice was taken of this. In 1823 Wohler dis- 

 covered the composition of cyanic acid ; in the follow- 

 ing year Liebig reported the same composition for 

 fulminic acid. These two bodies have the same 

 * Rep. Brit. Ass., for 1895, p. 649. 



