234 ANNALS OF THE MISSOURI BOTANICAL GARDEN 



(Vol 10 



struction of the acid anion, with the consequent release of basic 

 cations to be neutralized. Instead of being the cause of increasing 

 alkalinity, the neutralization of these basic ions by C0 a is in all 

 probability a means of keeping the solution from becoming even 

 more alkaline than it ordinarily does. 



The process of formation of intermediate metabolic products 

 from citrates is very obscure. The formula of citric acid is suf- 

 ficiently complex to permit of considerable adaptation to oxida- 

 tion, and a few directions which such processes might follow will 

 be indicated. 



Citric and malic acids are closely allied in structure and re- 

 actions. 



CBLCOOH 



Citric acid C(0H).C00H 



CH,.COOH 



CH(0H).C00H 



Malic acid 



CH,.COOH 



It is probable that the substituted OH group in these acids is 

 the path of easy chemical access to the citrate and malate mole- 

 cules. As was previously noted in connection with the oxidation 

 of the various acids, succinic acid was not oxidizable either by 

 permanganate or chromic acid, while malic (hydroxy-succinic) 

 and tartaric (di-hydroxy-succinic) were readily oxidized by both 

 substances, as is citric acid, which has a similar substitution. 

 Likewise, benzoic acid and phenol are oxidizable with difficulty, 

 whereas resorcin and phlorogluein are readily oxidized. More- 

 over, it is a general tenet of organic chemistry that compounds 

 containing substituted hydroxy groups are less stable usually 

 than the unsubstituted compound. 



Sando and Bartlett ('21) pointed out that malic acid in ex- 

 tracted fruit juices breaks down spontaneously in the presence 

 of toluol and chloroform to form succinic acid. Citric acid under 

 the same conditions might be expected to form tri-carballylic 



acid. Both succinic and tri-carballylic acids, especially the 



