CHAPTER I. 



INTRODUCTION. 



Agricultural Chemistry concerns itself with the chemical 

 composition of the food of plants and animals and with the 

 chemical changes involved in the processes of life. It has thus 

 to deal with the composition of soil, air and water, of the bodies 

 of plants and animals, of manures and other materials, and 

 with the chemical changes which these substances undergo. 



Before commencing the study of agricultural chemistry a 

 student should devote some time to acquiring a knowledge of 

 general chemistry. In this little work it is difficult to impart 

 such knowledge, and the reader should, if he has not already 

 had some training in the science, supplement what he reads 

 here by referring to some good modern text-book of chemistry* 

 This chapter will be devoted to a brief and necessarily very 

 incomplete sketch of the modern theory of chemistry, and of 

 the more characteristic properties of those elements which are 

 of importance in agriculture. 



According to present views, all matter (by which is meant 

 everything that possesses weight and which affects our senses) is 

 composed of minute particles, which are incapable of being sub- 

 divided and which cannot be destroyed. In view of the electron 

 theory of matter, and of some of the recent discoveries with 

 respect to radium and its conversion into helium, this statement 

 may have to be modified, but so far as the great majority of sub- 

 stances is concerned it may be accepted as true. Thus to the 

 mental vision of the chemist all materials, whether solid, 

 liquid or gaseous, are granular, inasmuch as they are com- 

 posed of countless multitudes of these indivisible particles. 

 Those particles are known as atoms (from two Greek words 



