508 CHEMISTRY OF ALCOHOLIC FERMENTATION. 



There is one difficulty in the way of explaining the formation 

 of the amyl alcohols by this hypothesis. They must be assumed 

 to originate in valerianic acid, which, according to KRUIS and 

 RAYMAN (II.) is formed, with other higher fatty acids, from 

 nitrogenous compounds of complex structure. Even though, 

 pace BRIEGER (I.), valerianic acid be actually capable of formation 

 from protein, it is hardly feasible to suppose that this alone forms 

 the source of the large quantities of amyl alcohol found in the 

 fusel oils. CAHOURS and DEMARCAIS (I.), it is true, state that fats 

 yield valerianic acid by chemical means on distillation with 

 superheated steam. Nevertheless, according to the highly im- 

 portant researches of EHRLICH (I.), both the amyl alcohols are 

 formed from leucin and isoleucin (the fission products of protein), 

 under the influence of the normal vital activity of yeast. D-leucin 

 forms the source of the levo-rotatory d-amyl alcohol, whilst r-leucin 

 is split up so as to form isoamyl alcohol and c^-leucin. About 87 per 

 cent, of the /-leucin is transformed by yeast into amyl alcohol. Ac- 

 cording to EFFRONT (XIV.), the autodigestion of yeast (see chap. 

 Ixvi.) forms another source of amyl alcohol, which, however, does 

 not begin to appear until the process has reached an advanced stage. 

 As the yeast cells die off, the formation of amyl alcohol ceases 

 a proof that this alcohol is produced, not by the vital activity of 

 the yeast cells per se, but by the action of an enzyme excreted by 

 the living cells. Hence, to a certain extent, Effront's opinion 

 is at variance with the results of Ehrlich's experiments and 

 consequently further investigation is required concerning the 

 formation of fusel oil. 



Methyl propylcarbinol, C 3 H 7 CH(OH)CH 3 , was discovered by 

 RABUTEAU (I.), and hexyl alcohol, namely, primary isohexyl, or 

 caproyl alcohol, (CH 3 ) 2 C 4 H 7 (OH), was detected, by FAGET (I.), in 

 the fusel oil of grape-husk spirit. According to K. WINDISCH 

 (III.), this alcohol occurs, in small quantity, in crude grain spirit ; 

 and it has also been found by KRUIS and RAYMAN (II.) in crude 

 potato spirit. 



The presence of small quantities of heptyl alcohol or cenanthyl 

 alcohol, C 7 H I5 .OH, was confirmed by K. WINDISCH (III.) in 

 crude grain spirit, and FAGET (II.) obtained it from grape-husk 

 spirit. Probably the alcohol recovered in the latter case was a 

 primary isoheptyl alcohol, (CH 3 ) 2 C 5 H 9 (OH). 



Finally, both normal and secondary nonyl alcohol, C 9 H 19 .OH 

 were discovered in crude potato spirit by HILGER (I.). 



According to ROMMIER (II.) the fatty acids and alcohols 

 produced during fermentation frequently combine while in the 

 nascent state to form esters, which are also formed during the 

 prolonged storage of fermented worts (wine) or distilled spirits 

 (cognac). These bodies constitute a large proportion of the 

 "bouquet" principles. The esters identified include the acetic 

 acid compounds of ethyl and amyl alcohol, and the corresponding 



