Vol. XV. No. 376. 



THE AGRICULTURAL NEWS. 



317 



ORGANIC AGRICULTURAL CHEMISTRY. By 

 J. S. Chamberlain, Ph.D., Professor of Organic and Agricul- 

 tural Chemistry in the Massachusett Agricultural College. 

 Neiv York: The Macmillan Company/, 1916. 



While intended primarily for use in agricultural colleges, 

 this book, treating of the chemistry of plants and animals, 

 should be appreciated by all those interested in the higher 

 branches of agricultural work. The arrangement of the 

 subject-matter is new; no hard and fast line is drawn 

 between the chemistry of plants and that of animals, and 

 this enables the reader to grasp the fundamental inter 

 relationships that exist between these two classes of living 

 organisms. 



The first section deals systematically with the 

 chemistry of the more important organic compounds 

 found in plants and animals. Beginning with hydro- 

 carbons, the principles of substitution and of isomerism 

 are explained, the lalter phenomenon being exhibited by two 

 compounds of identical composition, .such as the propyl 

 iodides, which have distinctly different properties. The 

 cyanides and amides are then discussed, followed by a section 

 dealing with the simple alcohols. This is followed by 

 information concerning the higher alcohols, and attention is 

 called to glycerine as an aleohol possessing three hydroxyl 

 groups. 



Chapter III concerns the oxidation products of alcohol, 

 namely aldehydes, and the fatty avids formed from these. 

 A note is given on oxalic acid, which is a polybasic acid. 

 The derivatives of alcohols and acids, namely esters, are then 

 dealt with in a very clear and interesting manner. These 

 esters are exactly analagous to metallic salts, the organic 

 radicle taking the place of the metal. Thus instead of lead 

 acetate we have ethyl acetate. Esters of the lower acids 

 and lower alcohols are pleasant smelling, volatile liquids 

 (hence the name ethereal salt). It is probable that the 

 odour of fruits is due to the presence of esters. Some of 

 these, like pine-apple essence, apricot essence, and pear 

 essence have been produced synthetically. 



Information is then given regarding waxes, fats and oils. 



When an alcohol neutralizes an acid, thereby forming an 

 ester, the process is termed esterification; and when in the 

 decomposition of a compound the addition of water is invol- 

 ved, the process is known as hydrolysis. Hydrolysis and 

 esterification are extremely important processes. In dealing 

 further with fats and oils the different chemical and physical 

 constants used for purposes of distinction are referred to. 



In Chapter V dealing with mixed compounds, an interest- 

 ing account is given of stereo-isomerism or space-isomerism, 

 illustrated by the three forms of lactic acid, and this is used 

 to lead up to the u.se of the polarisoope. The theory of the 

 symmetrical carbon atom is then explained, and after dealing 



with malic and tartaric acids, this chapter concludes with 

 a brief note on citric acid, which for students of tropical 

 agricultural chemistry we consider inadequate owing to 

 the importance of this compound. 



Chapter VI deals in a very clear manner with the amino 

 acids, proteins, ui-ea, and uric acid. A list of the principal 

 amino acids is given, and the physical classification of the 

 proteins outlinec'. The subject of the hydrolytic decom- 

 position of proteins is then dealt with to show the produc- 

 tion of amino acids as cleavage products. An instructive 

 section is devoted to the polypeptides, the study of which has 

 thrown much light upon the composition of the proteins. 



The study of uric acid leads to consideration of purine, 

 and this in its turn brings us to a consideration of the com- 

 position of the active constituents of cacao, coffee and tea. 

 Structural formulae are given for these substances, namely 

 theobromine and caffein. 



Chapter VII deals with the carbohydrates in the usual 

 clear and scientific manner which characterizes this text-book. 

 Various sugars and starches and celluloses are referred to, and 

 the chapter concludes with a treatment of unsaturated com- 

 pounds. 



The next part of the book. Section 2, is phj'siological, and 

 begins with a treatment of the subject of enzymes and enzy- 

 matic actions, thus striking at the outset a fundamental note 

 in both plant and animal physiology. Even the general reader 

 will read with interest the author's account of enzymic action, 

 in which reference is made to the zymogens — mother substances 

 from which enzymes are formed — and the co-enzymes and 

 anti-enzymes which regulate enzymatic action. The chapter 

 which follows deals in a general way with the composition of 

 plants and animals, special attention being given to the gen- 

 eral similarity between plant and animal cells. A straight- 

 forward account of animal food and nutrition, digestion and 

 absorption follows in Chapter XI. Space is devoted to an 

 account of hormones, which have received much attention from 

 physiologists in recent years. The following chapter deals 

 with animal metabolism, that is, the changes under which the 

 food goes after it has been absorbed into the animal system. 

 This chapter again is of general interest. On account of 

 their agricultural importance, nnlk, blood and urine are 

 specifically dealt with in a chapter to themselves. 



Plant physiology begins in Chapter XIV, and the subject 

 has reference principally to photo.synthesis or the production 

 of sugar in the green leaf through the agency of sunlight. 

 Then follows information on fats and proteins leading to 

 a statement of the nitrogen cycle. 



The remaining portion of the book is more economic 

 than the previous part. Space is given to a consideration of 

 the occurrence and uses of important constitutents in agricul- 

 tural plants. In this connexion tropical products are not 

 overlooked. Interest from the tropical standpoint attaches to 

 the information given regarding alkaloids, essential oils, 

 terpenes, and tannins. 



The last Chapter, No. XVII, concerns animal foods and 

 feeding. Food values are discussed and their determination 

 in calories explained. Information is given as to the energy 

 and food requirements of man and animals. 



It will be realized from the brief account that has been 

 given of the contents of this book, that it covers a range of 

 studies intimately associated with the successful production 

 of plant products and their utilization for feeding and 

 manufacturing purposes. Always a fascinating subject, 

 organic chemistry in relation to agriculture, as treated in thia 

 book, will be found especially so even by those who have 

 received but little previous training in the subject. 



