PREFACE 



THIS book is the outgrowth of instruction in chem- 

 istry given in the School of Agriculture of the 

 University of Minnesota since 1891. At first the classes 

 were small and individual work with blackboard exercises 

 and references to the literature in the school library was 

 possible. With increased numbers of students, mimeo- 

 graphed notes were supplied until finally the size of the 

 classes, and the volume of the notes have necessitated 

 their publication in book form. The work was first 

 given, in 1891, to a class of seven students, while twelve 

 years later they numbered nearly one hundred fifty. 



The class of students to whom this instruction has 

 been given have been mostly earnest workers who at- 

 tended school largely from personal choice and who de- 

 sired to make as much progress as possible. Numerous 

 questions have been asked by them relating to the ap- 

 plication of chemistry to farm and every-day life, and for 

 a number of years the author kept a question box in 

 which were placed the more important questions asked in 

 class, and the difficulties experienced in the laboratory 

 work, and in developing the work from year to year 

 these questions and difficulties have been considered. 



This work was originally outlined as Agricultural 

 Chemistry, but as special features have been developed 

 and published, as the "Chemistry of Soils and Fertil- 

 izers," and "The Chemistry of Dairying," this part of 

 the subject has gradually developed into "The Chemistry 



