CH. IX] INTRODUCTION. 239 



cedure, but knowledge of this kind must not be relied 

 on to the extent of substituting it for (qualitative 

 examination. 



For descriptions of the practical details of many of the 

 quantitative estimations, reference to standard works on 

 chemistry has been freely used. A full description is 

 given here only in cases where processes are required 

 which are not in general use, or where there is much 

 difference of opinion as to the best method of operating. 



The principles on which the methods of estimation 

 are based are generally explained in each case ; where 

 references only are given, care should be taken to under- 

 stand exactly the reasons for all the steps described in 

 text-books ; otherwise those who have not received an 

 adequate chemical training are liable to use instructions 

 of this kind in a merely mechanical way, and thus to 

 lose all the value of the work as an introduction to the 

 practical study of this branch of physiology, — where the 

 success of an operator largely depends on his ability to 

 modify methods to meet particular cases. 



Frequent references will be found in the text to the 

 following works. 



Sutton. Volumetric Analysis. 5th edit. (Churchill, 

 1886.) 



Fresenius. Qualitative Analysis. 10th English 

 edition. (Churchill, 1887.) 



Fresenius. Quantitative Analysis. 7th (or (ith) 

 English edition. (Churchill, 1876, 7th.) 



Beilstein. Handbuch der organiscJien Cheniie. 2nd 

 or 3rd edition. 



