618 HISTORY OF SCIENCE. 



all organic substances contain carbon as one of their constituents, and 

 subsequent analyses completely confirmed this. In 1828, however, 

 a German chemist named WOHLER discovered a method by which a 

 certain organic product called urea could be synthetically produced 

 from its elements in the laboratory. This fact was sufficient of itself 

 to break down the barrier which had been supposed to separate the 

 two provinces of chemistry. But it was not until many years after- 

 wards that other facts of this kind were discovered. Some progress was 

 made in 1845 and 1846, and in 1850 Professor FRANKLAND (born 1825) 

 found a means of combining certain alcohol radicals with zinc, and this 

 again showed the continuity of the two arbitrarily separated departments 

 of chemistry. Before this a distinction had been made which superseded 

 the older idea of the supposed necessity of the intervention of peculiar 

 vital forces in the production of organic compounds. Organic che- 

 mistry was defined as embracing the study of all compounds of carbon. 

 There were obvious advantages in studying these compounds apart, 

 on account of their great number and of certain peculiarities in the che- 

 mical behaviour of carbon. The distinction, however, is now held to be 

 quite arbitrary, although convenient. After Frankland's discovery of 

 the organo-metallic compounds, methods of forming by artificial syn- 

 thesis many complex organic compounds were made known by the 

 labours of several distinguished chemists. From what has been already 

 accomplished, it is reasonable to believe that in the progress of the 

 science it may come to pass that all organic compounds will be ob- 

 tainable by the processes of the laboratory. A striking instance of 

 what can be effected by such processes may be cited in the discovery 

 in 1869 of a mode of artificially preparing alizarine, the tinctorial 

 substance in madder the well-known Turkey red dye. Artificial 

 Turkey red is now manufactured in large quantities from anthracene, 

 a compound of hydrogen and carbon obtained in the distillation of 

 coal-tar, and thus the necessity for cultivating the madder-plant is 

 obviated. 



The study of the carbon compounds was the means of introducing 

 many new theoretical ideas into chemistry. An account of these 

 theories in connection with the facts they were invented to represent 

 would carry us far beyond our limits, and without a discussion of the 

 facts they would be empty and unintelligible to the general reader. 

 We shall not attempt even a statement of modern chemical theory, 

 but notice only one or two points merely as an illustration. Hence 

 we pass over the conflict of " nucleus," " type," " substitution," and 

 other theories, to which the discoveries of organic chemistry especially 

 gave rise. But it will be incumbent upon us to refer to the labours 

 of the great master of organic chemistry Justus von Liebig. 



JUSTUS VON LIEBIG, born at Darmstadt in 1803, died 1873, was 

 one of the greatest scientific men of his age. He did for organic 

 chemistry that which Lavoisier did for inorganic : he may be said to 



