98 Indianapolis Biocheinical Meeting: Ahstracts [Sept. 



of magnesium to phosphorus. The differences in the amounts and 

 Proportion of ash constittients appear sufficiently well marked to 

 indicate a more or less definite correlation in the metabolism both 

 of healthy and of diseased plants. {Phyto pathology, 191 1, i, p. 



159) 



The Effect of Frost on the Aromatic Constituents of the 



Peppermint Plant 



FRANK RABAK 



{Office of Drug Plant, Poisonous Plant, Physiological and Fer- 

 mentation In-uestigations, Bureau of Plant Industry, 

 Department of Agriculture.) 



The oil from plants {Mentha piperita, L.) frozen November 26, 



v/as compared with the oil distilled earlier in the same season from 



plants in the same stage of growth (12-18 inches in height without 



buds and consisting largely of leaves). Some of the differences 



■•reported are given in the f ollowing table : 



Oil from frozen plants. Oil from normal plants. 



Specific rotation — 25.2° — 18.4° 

 Readily soluble in 80 per cent. alcohol in excess. Turbid in ij^ vols. or more. 



Acid number 0.9 0.8 



Ester number 97.4 25.2 



Acetylization number 206. 126. 



Menthyl Acetate 34.3 per cent. 8.8 per cent. 



Free Menthol 40.7 per cent. 31.8 per cent. 



The Chief effect of frost was therefore to increase the esters 

 and also to a certain extent, the free menthol. It has been sug- 

 gested that esterification is the result of a reversible enzyme reaction 

 checked by water, since any condition which accentuates the elimina- 

 tion of water favors esterification in the plant. The author sug- 

 gests that the mechanism of the action of freezing may be to check 

 the absorption of water and possibly to render iiseless the water 

 circulating in the plant. Esterification by aid of an enzyme with a 

 catalytic action may have continued, the water formed being re- 

 moved by freezing and thus mitigating the chance of a reverse 

 reaction. 



