550 REUBEN L. KAHN 



(1) The close relation which exists between alcohol, aldehyd, 

 and acid is well illustrated by the following equations. If we 

 take ethyl alcohol as our specific example, we have: 



1. CH3CH2OH + O = CH3.CHO + H2O 

 Ethyl alcohol Acetaldehyd. 



2. CH3CHO +0 = CH3.COOH 



Acetic acid. 



Thus, by oxidation. Alcohol -> Aldehyd -^ Acid 



and inversely by reduction Acid -^ Aldehyd — > Alcohol. 



It is generally believed that oxygen from the air can not 

 effect the oxidation from alcohol to acid except through the 

 agency of ''catalyzers" or ferments. 



(2) The close relation which exists between aldehydes and 

 ketones can be seen from the following: 



The oxidation of primary alcohols yields aldehydes, and the 

 oxidation of secondary alcohols yields ketones — thus 



CH3.CHOH.CH3 + O = CH3.CO.CH3 + H2O 



Secondary propyl alcohol Dimethyl ketone or acetone. 



(3) From a chemical standpoint, the carbohydrates are 

 aldehyd or ketone derivatives of polyhydric alcohols. This is 

 illustrated by glancing at the structural formula of atypical 

 sugar, glucose, and the two alcohols, mannitol and glycerol.* 



1. Glucose = CH2(0H) CH(OH) CH(OH) CH(OH) 



CH(OH) CHO 



2. Mannitol = CH2(0H) CH(OH) CH(OH) CH(OH) 



CH(OH) CH2OH 



3. Glycerol = CH2(0H) CH(OH) CH2(0H) 



(4) The production of lactic acid from lactose by a number of 

 organisms, including B. coli, has led some investigators to the 

 opinion that the reddening of colonies produced by B. coli on 

 Endo medium is due to lactic acid. It is indeed likely that the 

 formation of lactic acid is an important intermediary step in 

 the production of typically metallic colonies on . Endo agar. 

 However, when the alcohol, glycerol, is substituted for lactose in 



