1892.] NEW YORK ACADEMY OF SCIENCES. Ill 



of these elements differ from those with which inorganic nature 

 presents us." 



In other cases the chemists of that time believed in the action of 

 what they called a vital force, which acted in the formation of 

 organic compounds and not in the case of inorganic compounds. 

 They said it is easy to take organic substances to pieces and I'esolve 

 th«u into simpler compounds, but to build them up from their ele- 

 ments was an impossibility without the intervention of vital force. 

 Thus we could convert the complex substance grape-sugar into 

 alcohol and carbon dioxide, but it took vital force to make the sugar 

 in the grapes and other vegetable substances that contain it. 



The first good blow against the vital-force theory was struck in 

 1828, when Wohler succeeded in making urea artificially by boiling 

 an alcoholic solution of ammonium cyanate, thus from purely inor- 

 ganic materials l)uilding up a substance as truly organic as any we 

 can find in the animal or vegetable kingdoms; but even this master- 

 stroke of a master-hand did not at once overthrow the theory of 

 vital force, although the best minds in the chemical world saw its 

 power and the tendencies of the researches that would be made in 

 the future. 



Liebig, Berzelius, Dumas, and BouUay all worked upon organic 

 bodies with a view to determine their constitution. The constitu- 

 tion of oil of bitter almonds, discovered by Liebig and Wohler ; the 

 discovery of ethyl in alcohol by Berzelius and Liebig ; the formation 

 of aldehyde and acetic acid ; formic acid from methyl alcohol or 

 wood-spirit ; the discovery by Liebig of chloride of methenyl or 

 chloroform, and also chloral, all followed as the early fruits of this 

 organic research. 



And while we are talking of Liebig, it is interesting to note that 

 his father was a wholesale druggist, and his own first knowledge of 

 chemistry began while he was an apprentice to an apothecary at 

 Heppenheim, near Darmstadt. It was in this position that ho made 

 some of his first experiments upon the fulminates, and having the 

 misfortune to cause a great explosion his term of apprenticeship 

 was soon ended. Liebig afterward made a number of interesting 

 contributions to chemical knowledge. It was he that obtained 

 picric acid from aloes, although aloin was not discovered and iso- 

 lated until more recently. In 1829 Liebig discovered hippuric acid ; 

 but the work that made him most famous was his improvements 

 in the methods of organic analysis In old times when a chemist 

 wished to find out what a substance contained he put it into a retort 

 and heated it, or, as we say, subjected it to dry distillation He 

 then obtained a watery liquid, afterward some oily matters, and 

 an alkali in the case of animal substances, which he soon learned 

 was ammonia; but there were also obtained certain gases which 

 he did not collect, and a mass of carbon remained in the retort. 

 But Liebig had learned that organic bodies contained carbon, 

 hydrogen, oxygen, and nitrogen, and he perfected the methods 



