PREFACE 



It has been the aim in this manual to 

 select substances of agricultural interest, 

 adapt them to laboratory preparation, and 

 explain their chemistry to the best of our 

 present knowledge not overlooking their 

 practical significance. 



The work was at first nothing more than 

 laboratory directions, but the interest of the 

 student gradually required the addition of 

 explanatory matter to such a degree that 

 the emphasis on an accompanying text has 

 been greatly reduced. The method of pres- 

 entation aims to put a few major points 

 before the student and extend the work on 

 such points over so long a time that the 

 student will absorb it. The author feels 

 that when a student, in his earlier years in 

 college, works interestedly for a whole exer- 

 cise around one thing he grasps something 

 while if a dozen important points pass in 

 review during the time he is left in a maze 

 and gets little but technical benefit. While, 

 however, the student is busy on the one 



ill 



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