PREFACE 



Agricultural chemistry is a subject presenting two quite 

 distinct lines of study. The study of soils and fertilizers, includ- 

 ing the relation of the plant to its soil food, is almost wholly 

 inorganic and physical. On the other hand, the study of plants 

 and animals as living organisms is as distinctly organic and 

 physiological, embracing the greater part of what is termed Bio- 

 chemistry. 



This has led the author to prepare one part of a textbook of 

 General Agricultural Chemistry with this distinction in view, 

 and to designate it as Organic Agricultural Chemistry — The 

 Chemistry of Plants and Animals. The companion volume on 

 Inorganic Agricultural Chemistry — The Chemistry of Soils 

 and Fertilizers — is being prepared by the author's associate, 

 Dr. Ernest Anderson. 



The author believes that there is a place in our Agricultural 

 Colleges for a course covering the work included in these two 

 volumes with the definite aim of giving to students of practical 

 agriculture enough general scientific instruction in chemistry to 

 enable them to understand and correlate the broad problems 

 of agricultural practice. The course covered by the two books 

 has been planned to follow a course in general chemistry such 

 as is given in the Freshman year in most colleges, and assumes 

 a knowledge represented by such work. 



The present volume does not pretend in any sense to re- 

 place the more thorough study of both organic and physiological 

 chemistry by those students preparing to be chemists or other 

 scientific workers in agriculture. Assuming that the student 

 has not had a special course in systematic organic chemistry, 

 there is included, as Section I, the essentials of such a study as 

 related directly to agriculture. Following this systematic study 

 of organic chemistry the treatment in Section II is largely 



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