IV PREFACE. 



This book thus appeals to chemists, botanists, and biologists, 

 likewise to those technologists who are engaged in the branches 

 of industry named. 



In the bibliographical list I have included all important 

 works of the older and more recent literature which are of 

 interest to the scientist and technologist. 



In its present form this book in the main has the same 

 scope and contains the same matter as the third completely 

 revised Grerman and the French editions. 



ALFKED JORGENSEN. 

 Copenhagen, 

 May, 1893. 



