TRANSLATOR'S PREFACE. 



ONE of the chief difficulties which arose in the preparation of 

 this translation was with regard to the proper spelling of the com- 

 pounds mentioned. Many of them have not been described much in 

 English, so that English-speaking scientists are often better acquainted 

 with the German orthography. Some of the chemical compounds have 

 been spelled in three different ways by writers of good English. This 

 would almost lead one to believe that there is no good authority in 

 English for the spelling of chemical names. Many writers have followed 

 the German spelling as nearly as possible in describing compounds which 

 have hitherto been mentioned only in German literature. This must 

 necessarily lead to confusion, particularly because the ending e in German 

 usually signifies the plural, whereas it does not in English. The Chemical 

 Society of London in its Abstracts has mentioned nearly every sub- 

 stance touched upon in this book and has adopted certain rules for 

 spelling which its abstractors are required to follow. These rules have, 

 in the main, been adopted by the American Chemical Society and the 

 American Chemical Journal. According to these rules, (1) All hy- 

 droxyl derivatives of hydrocarbons should end in ol, thus glycerol, 

 resorcinol and mannitol rather than glycerine, resorcin and mannite. 

 (2) Compounds which are not alcohols and have names ending in ol 

 should be written ole, as anisole, indole. (3) When a substituent is one of 

 the groups NH 2 , NHR, NR 2 , NH or NR its name should end in ine, thus 

 aminopropionic acid and not amidopropionic acid. (4) The ending ine 

 should be reserved for these basic substances, as aniline instead of anilin, 

 and the termination in should be reserved for glycerides, glucosides, 

 bitter principles and proteins, such as palmitin, amygdalin and albumin. 

 It seems to us that these are the best rules for English-speaking chemists 

 to follow at present. The rules cited are those which pertain particu- 

 larly to the substances described in these lectures. 



In two cases we have intentionally deviated from the practice of the 

 above-mentioned chemical journals. We have used the word ferment to 

 designate "that which is capable of causing fermentation" (Century Dic- 

 tionary) and have not attempted to distinguish between ferments and 

 enzymes. This distinction was based upon an error, as Buchner has so 

 positively shown, and has led to much confusion. Again, we have fol- 

 lowed the author rather than the chemical journals with regard to the 



