PRODUCTS OF ACETOUS FERMENTATION. 41 



weeks a quite thick fluid of an agreeable odor has collected upon 

 the glass plate. This is collected and distilled, the portion passing 

 over at 219 F., being collected by itself. 



Pure acetal is composed of C fi H l4 O 2 . It is a colorless liquid, 

 has a specific gravity of 0.821, and boils at 219.2 F. It has a 

 refreshing odor, calling to mind that of fruit ethers. By oxi- 

 dizing agents it is quickly converted into acetic acid. Nitrate of 

 silver in the presence of ammonia is, however, not reduced by it, 

 and it remains unchanged on boiling with potash lye. From its 

 composition acetal may be considered from several points of view. 

 It may be regarded as an ethyl alcohol (glycol) C 2 H 6 O 2 , in 

 which two atoms of hydrogen have been replaced by two mole- 

 cules of the radical ethyl C 2 H 5 , hence thus 



f } - ^hyl-glycol 



C 6 H 14 O 2 acetal. 



This view of the composition of acetal is supported by the fact 

 that methyl or amyl can be substituted for either one or both mole- 

 cules of ethyl in the combination. 



According to other opinions, acetal may be considered as a com- 

 bination of aldehyde and aldehyde ether : 



C 2 H 4 O aldehyde 



C 4 H 10 O aldehyde ether 



C 6 H, 4 O 2 acetal, 



or as a combination of aldehyde with ethyl alcohol, one molecule 

 of water in the latter having been replaced by the aldehyde : 



Ethyl alcohol : 2(C.H 6 O) JI 2 O = C 4 H/) 



aldehyde C 9 H,O 

 acetal C 6 H J4 O 2 



By keeping in view the fact that the process of the formation 

 of vinegar is an oxidation of the alcohol which does not proceed 

 with equal energy in all parts of the apparatus, it will be under- 

 stood that during this process aldehyde, acetal, and acetic ether 

 can be formed which, if the operation be correctly conducted, will 

 be finally converted into acetic acid, though small quantities of 

 them will be found in the vinegar when just finished and exert 

 an influence upon its constitution. 



