500 Transactions of the American Institute. 



vinegar is simply a solution of this acid mingled with more or less of 

 foreign substances. The chemistry of vinegar making is this : The 

 saccharine matter in the cider or other liquid absorbs oxygen from the 

 air and is converted into alcohol, and then the alcohol unites with 

 more oxygen and becomes acetic acid, Yinegar that contains five 

 per cent of pure acetic acid is the strongest ever known in the trade ; 

 and an article that, by testing, would show three and one-half per 

 cent, would doubtless be quite strong enough for pickles. 



Adjourned. 



January 12, 1869. 



Mr. Nathan C. Ely in the chair ; Mr. John W. Chambers, Secretary. 



Caee of Sweet Potatoes. 



Mr. F. G. Carey, Buckeye Farm, Butler county, Ohio. — It may 

 not be amiss before I give you my method and experience to say 

 something of the physiology or peculiar structure of this tuber. It 

 will account for what to many seems so mysterious and difficult in its 

 preservation. By examination you find it made of thread like fila- 

 ments surrounded by a delicate cellular tissue. These filaments run 

 longitudinally throughout the entire potato, and are filled with milk, 

 or milk and water, which on breaking will be seen to exude very 

 quickly and profusely. These filaments form a bundle at the stem 

 end of the potato, and are feeders of the tuber, so to speak. These 

 threads, filled in their normal condition with this fluid, when the 

 potato is exposed to a temperature of twenty degrees, thirty minutes, 

 become enlarged or swollen by reason of that remarkable law, accord- 

 ing to which water increases in volume at this hygrometric point of its 

 temperature, and are ruptured, and discharge their contents into the 

 tissue while more or less contracted, and the potato decays at once. 

 The same result is liable to follow from sudden dampness. The sweet 

 potato, therefore, in an atmosphere at any temperature from thirty-two 

 degrees to thirty-nine degrees, thirty minutes, will soon decay. And 

 this is in perfect conformity with the law above stated. Numerous 

 experiments have convinced me of the correctness of this statement. 

 The Irish potato is entirely different in its structure, being composed 

 of cells of uniform density, and is preserved at any point above freez- 

 ing. Now, my experience for many years has been, if you place your 

 sweet potatoes in bulk, as you do your Irish potatoes, in the place 



