y 



PREFACE TO THE THIRD EDITION 



With the exception of a few corrections and additions, this is 

 a reprint of the last edition. In an elementary book of this 

 kind the introduction of the results of recent work on the 

 constitution and digestion of proteids may safely wait until 

 the main facts and principles are more fully elaborated by the 

 active investigations which are now being made. Doubtless, 

 in the near future, a conception of the whole process of diges- 

 tion will be reached, clear enough for easy presentment to 

 even elementary students. 



Lbbds, October 1919. 



PREFACE TO THE FIRST EDITION 



This little volume is based upon the writer's long experience 

 in teaching agricultuml students, among whom there are, 

 unfortunately, many who cannot devote the time necessary to 

 acquire sufficient knowledge of pure chemistry to profitably 

 read such works as the author's "Manual of Agricultural 

 Chemistry." * 



It is true that any attempt to combine, in one book, 

 instruction in the principles of general chemistry with the 

 somewhat technical information concerning the chemistry of 

 agriculture, must be in many ways a failure, and the author 

 would strongly recommend the user of this work to read some 

 good, modern text-book on the former ; or, better perhaps, to 

 ask his teacher to explain, at greater length, the very incom- 

 plete and sketchy accounts which are given of the jirinciple° 

 of chemistry and of the properties of the elements and com- 

 pounds important in agriculture. 



While fully realising that a satisfactory knowledge of 



agricultuiul chemistry cannot be acquired without a previous 



training in pure chemistry, he is aware that there are many 



agricultural students and farmers who have, perforce, to do 



 Scott, Greenwood & Son, London. 



47^274 



