CARBOHYDRATES 135 



previously to them, we would next come to compounds in which 

 carbon groups instead of being joined together in open chains, 

 either straight or branched, are united to each other in the form 

 of a closed chain or ring. Such compounds are known as car- 

 hocydic compounds. Chief among all the carbocyclic hydro- 

 carbons is the well-known substance benzene (not benzme) 

 which is obtained from coal tar. The name benzol, which is 

 German, also apphes to this compound. The derivatives of 

 this hydrocarbon benzene (CeHe) are even more numerous than 

 those of methane, and many of them are of the greatest industrial 

 importance in connection with dyeing, medicine and numerous 

 industries and arts. The coal tar dyes, or aniline dyes, are 

 derivatives of this class, and will suffice to give some indication 

 of the importance of the compounds yet to be considered were 

 we to complete our study of the compounds of carbon. 



Few of the compounds of this large series are, however, of any 

 direct importance in agriculture, and as in their study we should 

 gain no new general ideas of value to us in connection with agri- 

 cultural chemistry we shall not do more than mention them in 

 this very brief way. We shall thus bring to a conclusion at this 

 point our study of the organic compounds. 



References J Section I 



Abderhalden, Neuere Ergebnisse der Eiweisschemie, 1909. 



Armstrong, The Carbohydrates and Glucosides (Monographs on Bio- 

 chemistry), 191 2. 



Cohen, Organic Chemistry for Advanced Students, 1913. 



Diels, Organische Chemie, 1909. 



Holleman-Walker, Text -book of Organic Chemistry, 191 1. 



Holleman-Walker, Laboratory Manual of Organic Chemistry, 1913. 



Leathes, The Fats (Monographs on Bio-chemistry), 1910. 



Lewkowitsch, Chemical Technology and Analysis of Oils, Fats and 

 Waxes, 191 5. 



Mandel, Handbook for Bio-Chemical Laboratory, 1896. 



Meyer and Jacobson, Lehrbuch der Organischen Chemie, 1893. 



Molinari-Pope, General and Industrial Organic Chemistry, 1913. 



