188 REPorRT OF THE CHEMIST OF THE 
ment of Agriculture, performed most of the routine analytical 
work required by the investigation. 
In the process of making vinegar from apple juice or “ sweet 
cider,” two fermentations are prominent and essential. Through 
the agency of the first form of fermentation, the sugars of the 
apple juice are converted into alcohol, and the product at this 
stage is commonly known as “hard” cider or simply cider. The 
alcohol is then converted by another form of fermentation into 
acetic acid, the product then being known as vinegar. In con- 
sidering the formation of cider-vinegar, we have therefore to study 
two distinct processes of fermentation. 
THE COMPOSITION OF APPLE JUICE. 
Before considering the changes produced in apple juice by the 
fermentations that convert it into vinegar, we will study the 
composition of the juice freshly prepared from apples. In the 
preparation of the samples of apple juice used in our work, we 
selected standard varieties of apples; we used only well-ripened, 
sound fruit and prepared the samples in October and November. 
Before grinding, the apples were washed and then put through 
a large-sized hand-mill and press. 
The apple juice was filtered before analysis in order to remove 
pulp and other suspended matter. The determinations in the 
apple juice, cider and vinegar were made as follows :— 
The specific gravity was determined by means of a pyknometer. 
The solids were found by drying about five grams of material 
on sand in a steam oven for six to eight. hours. 
The sugars were determined by the volumetric permanganate 
method, as described in Bulletin No. 46 of the Division of 
Chemistry, United States Department of Agriculture, p. 38. 
The amount of total acid was found by direct titration. The 
volatile and fixed acids were determined as follows: About 10 
grams of material were evaporated to dryness on a water bath, 
then a small quantity (about 5 ee.) of distilled water was added 
and the contents evaporated to dryness again. The addition of 
water and evaporation to dryness were repeated two or three 
times. The residue was then titrated with decinormal sodium 
hydroxide and the result calculated as malic acid. This amount 
