The estimation of the tartaric acid is of value, because this is the characteristic acid of wine, and is not present in some fruit juices which might be used as adulterants - e.g., apple. and pear. juices. Malic acid is especially characteristic of apple juice, though wines also contain it. Citric acid may help to indicate the presence of gooseberry or currant wine. The volatile acids are of importance as showing the progress of acetous fermentation, and their proportion is used in France for calculating certain ratios employed as criteria of genuineness.