The total acidity of wines may be determined by titration with

N/5 or N/10 alkali. The end reaction may be observed by means of a drop brought into contact with delicate litmus paper, which, while not entirely satisfactory, still is probably the best method we have at hand, any means for decolorizing the wine so as to admit of the use of other indicators being likely to change the content of acid. I have found that by the use of turmeric paper in connection with the litmus, the establishment of the point of neutralization is greatly facilitated.

1450 - No. 13, pt. 3 --- 6

Very white wines, if entirely free from carbonic acid, may be titrated with phenol-phthaline as an indicator. From 10 to 25cc. of wine may conveniently be taken for titration. It is very desirable to estimate both the fixed and volatile free acids in wine, and to this end the latter should be determined directly; all methods for this estimation by difference by evaporating the wine to dryness, and titrating the residue, having been shown to be faulty. The German method is to distill off the acetic and other volatile acids in a current of steam; and I have found it a most satisfactory one, giving very coincident results when carefully carried out, the only objection being that it is a little tedious. The theory of the method is that acetic acid, which forms the greater part of the pure volatile acids, while it does not distill off at a temperature lower than 120° C, can still be distilled off at a lower temperature than its boiling point by passing through the liquid in which it is contained a current of steam, providing that the quantity of water passed through in the shape of steam is about four times as great as the quantity of the liquid in which the acid is contained. The manner of applying it is as follows:

Fifty cc. of the wine are measured into a flask of about 300cc. capacity, which is connected with a condenser by one tube which passes just below the rubber stopper, which is also perforated by another tube which reaches to the bottom of the flask and terminates there in a finely drawn out point; this tube is bent at right angles where it passes out of the flask, and connects it with a larger flask placed alongside which contains about 300cc. of water, being also provided with a safety tube. When the operation is begun, lamps are placed under the two flasks and the contents of both brought to a boil, when the flame under the flask containing the wine is lowered somewhat and the distillation so conducted that after 200cc. have distilled off the wine shall not be decreased to less than onethird or one-fourth of its original volume. The 200cc. of distillate is received in a properly graduated flask, and titrated with standard alkali, using phenol-phthaline as an indicator.

The number of cubic centimeters of normal alkali required for the titration of the volatile acids, subtracted from the number of cubic centimeters required for the neutralization of 50cc. of the original wine, gives the amount of alkali neutralized by the free fixed acids; the total free acids and free fixed acids are generally calculated as tartaric, the volatile as acetic acid.1