New York AGRICULTURAL EXPERIMENT STATION. 235 
when once the acetic acid has been formed. In practice, this can 
be done by drawing off the clear vinegar, placing it in a clean 
barrel, filling it as full as possible and putting the bung in tight. 
5. BEHAVIOR OF MALIC ACID OF APPLE JUICE [N VINEGAR-MAKING. 
Malic acid was found to decrease during the vinegar-making proc- 
ess. In most cases, only small amounts of malic acid, free or com- 
bined, were left when the vinegar had become a commercial product. 
In decomposed vinegars, malic acid had entirely disappeared. Malic 
acid added to apple juice also disappeared to a large extent. In 
sterilized apple juice, the decrease of malic acid was less marked. 
The white precipitate formed when lead acetate is added to vine- 
gar has been attributed to the presence of malic acid in the vinegar, 
-and a vinegar failing to give this test is usually regarded as not 
cider vinegar. While all of our vinegars gave a precipitate with lead 
acetate, there were several in which no trace of malic acid was 
present. Such a white precipitate with lead acetate is due, not to 
malic acid, but to the phosphates in vinegar. 
6. THE SOLIDS OF APPLE JUICE AND CIDER VINEGAR. 
During the first three months of the alcoholic fermentation at 
cellar temperature, the solids decreased rapidly. The loss was not 
uniform in different experiments. There is quite generally a de- 
crease of solids to a point below 2 per ct., but under normal condi- 
tions there is a subsequent increase. In old vinegars, standing in 
barrels with the bunghole open, there is evaporation of water and a 
consequent increase of solids. In vinegars in which a destructive 
fermentation of acetic acid has occurred, there is also a marked loss 
of solids. The amount of vinegar solids may be below 2 per ct 
when the acetic acid is above 4.5 per ct. 
7. CIDER VINEGAR IN RELATION TO LEGAL STANDARDS. 
Legal standards for cider vinegar are usually based upon the per- 
centage of acetic acid and cider-vinegar solids. In New York State, 
the legal requirement is 4.5 per ct. of acetic acid and 2 per ct. of 
solids. From our work, it appears that where proper fruit is used 
for cider-making and where the conditions of fermentation are 
properly controlled, there should be no difficulty in making cider 
vinegar that contains above 4.5 per ct. of acetic acid in 18 to 24 
months. 
