ALCOHOL 57i 



more nearly that of ethyl, it is practically impossible, even by repeated 

 fractional distillation, to remove all traces of these. 



The alcohols with a higher boiling point are also found to differ 

 from ethyl alcohol in another respect — that is, in their chemical form 

 or molecular weight. The molecular weight of ethyl alcohol taken as a 

 standard is 46; that of propyl, 60; that of butyl, 74; and that of 

 amyl, 88. It is thus seen that in both molecular weight and boiling 

 point, alcohols of fermentation fall into a regular series ascending 

 from ethyl to amyl. 



In addition to the above alcohols of fermentation is wood or methyl 

 alcohol which reaches its boiling point at only 66° C. (or 66.5°) and 

 has a molecular weight of 32. 



The molecular weights and boiling points found for the primary 

 alcohols named may be briefly summarized as follows : 



Alcohol Molecular Weight Boiling Point 



Methyl 32 66.0° C. 



Ethyl 46 78.4° C. 



Propyl 60 97.0° G. 



Butyl 74 117.0° C. 



Amyl 88 132.0° C. 



The Biological Significance of Fermentation 

 While the production of alcohol has long been associated in the 

 minds of all peoples with the process of fermentation, yet the exact 

 nature of the process was unknown until the significant work of 

 Pasteur appeared. Pasteur in his work on fermentation, as in all his 

 work, was unwilling to accept blindly an interpretation of the meaning 

 of the process until he had examined in detail and elucidated step by 

 step the actual occurrences taking place. 



By taking the juice of the grape he observed, as had often been 

 observed before, that upon leaving it for a time at a warm temperature, 

 bubbles of gas arose. This gas was evidently the result of a chemical 

 process going on within the mixture. But to Pasteur is due the credit 

 of showing for the first time that within the mass of grape juice the 

 thousands of living organisms (which Latour, Schwann and others 

 had already seen) were busily engaged in the process of digesting a part 

 of the sugar contained in the juice. Pasteur believed that these living 

 organisms, by taking oxygen from the sugar, caused the splitting up of 

 the sugar into two substances. One of these he had seen arising as 

 bubbles of gas — carbon dioxide — the other remained in the mixture, 

 gradually increasing in strength as more and more was produced. The 

 latter substance Aristotle had spoken of as the exhalation of wine. 

 Marcus Grsecus denominated it aqua ardens. We call it alcohol. The 

 organisms which thus produce alcohol are the yeasts, many kinds of 

 which are now known. 



To Pasteur fermentation was life without air. That is, the yeasts 



