168 REporRT OF THE CHEMIST OF THE 
low temperature, (4) lack of air, due either to filling the barrel 
too full or stopping the bung-hole. 
(1) Dirty fruit—lIt is quite common that the apples used for 
vinegar-making are refuse left lying on the ground until they 
become covered with soil and more or less decayed. Under such 
conditions, there is serious danger of getting into the apple juice 
organisms that will interfere with the regular alcoholic and 
acetic fermentations, particularly the latter, either by lessening 
the amount of those products or by producing undesirable 
flavors. 
(2) Unclean barrels.—Barrels or casks are frequently used 
for vinegar-making, which are not previously cleaned, no matter 
what their previous condition or use. Undesirable organisms 
may be brought into contact with the apple juice in this way. 
(3) Storing apple juice at too low temperature.—Many, if not 
most, farmers place their barrels of apple juice at once in the 
coc! temperature of a cellar, where it will usually require 6 
months or more to complete the alcoholic fermentation. The 
material is left at the same temperature for the acetic fermenta- 
tion which takes place with extreme slowness. In some cases, 
it may require three years or more before the acetic fermentaiton 
is completed under these conditions, and ordinarily the time is 
two years or more. 
(4) Lack of air.—The acetic fermentation requires the pres- 
ence of air, and this may be excluded by filling the barrel too 
full or by putting the bung in tight or by doing both at once. 
It often happens that the conditions have all been favorable and 
that the vinegar is apparently sour enough; the bung is then 
tightly stoppered, when an analysis would show less than 4 per 
ct. of acid. Before closing the barrel it would be well to have 
the amount of acid determined as soon as the vinegar seems suffi- 
ciently sour. When the barrel is thus tightly stoppered before 
the formation of acid is completed, the fermentation soon ceases 
and the amount of acid does not increase further. 
LACK OF PROPER CARE AFTER ACID IS FORMED. 
When the alcoholic fermentation is completed and the cider 
has become commercial cider vinegar of good quality, destruc- 
