The German Commission gives two methods, as follows :

In two stoppered flasks two samples of 20cc. of wine each are treated with 200cc. ether-alcohol (equal volumes), after adding to one flask 2-3 drops of a 20 per cent. solution of acetate of potash. The mixtures are well shaken and allowed to stand 16 to 18 hours at a low temperature (0-10oC), the precipitate filtered off, washed with ether-alcohol, and titrated. (The solution of acetate of potash must he neutral or acid. The addition of too much acetate of potash may cause the retention of some bitartrate in solution.) It is best on the score of safety to add to the filtrate from the estimation of the total tartaric acid a further portion of 2 drops of acetate of potash to see if a further precipitation takes place.

1 One cubic centimeter of normal alkali neutralizes .075 gram of tartaric, .06 gram of acetic acid.

In special cases the following method is recommended for a control over the other:

Fifty cc. of wine are evaporated to the consistency of a thin sirup (best with the addition of sand), the residue brought into a flask by means of small washings of 96 per cent. alcohol, and with continual shaking more alcohol is gradually added, until the entire quantity of alcohol is about 100cc. The flask and contents are corked and allowed to stand 4 hours in a cool place, then filtered, and the precipitate washed with 96 per cent. alcohol; the filter paper, together with the partly flocculent, partly crystalline precipitate, is returned to the flask, treated with 30cc. warm water, titrated after cooling, and the acidity reckoned as hitartrate. The result is sometimes too high, if pectinous bodies separate out in small lumps, inclosing a small portion of free acids (this error may, however, be avoided by the addition of sand and thorough shaking). In the alcoholic filtrate the alcohol is evaporated, 0.5cc. of a 20 per cent. potassic acetate solution added, which has been acidified by a slight excess of acetic acid, and thus the formation of bitartrate from the free tartaric acid in the wine facilitated. The whole is now, like the first residue of evaporation, treated with (sand and) 96 per cent. alcohol, and carefully brought into a flask, the volume of alcohol increased to 100cc. well shaken, corked, allowed to stand in a cold place 4 hours, filtered, the precipitate washed, dissolved in warm water, and titrated, and for 1 equivalent of alkali 2 equivalents of tartaric acid are reckoned. This method for the estimation of the free tartaric acid has the advantage over the former of being free from all errors of estimation by difference.

I have preferred making the qualitative test for free tartaric acid separately from the bitartrate estimation, and for the latter I have used essentially the first method given, omitting, of course, the parallel precipitation with the addition of acetate of potash, modifying it by using only 80ec. of the alcohol ether solution for the precipitation and allowing it to stand over night. The titration is nicely performed with phenol-phthaline and decinormal soda with white wines; 1cc. decinormal soda corresponding to .0188 grams of potassic hitartrate. In the case of dark colored wines I passed them first through a small amount of bone-black, afterwards washing the bone-black thoroughly, so as to avoid the presence of coloring matter in the tartar precipitate.