This acid is regarded as a normal constituent of most wines, and especially of old wines. The following method of estimating it, due to Mœslinger,1 depends upon the fact that barium lactate is soluble in strong alcohol, whereas the other barium salts present are insoluble in this medium.

1 Zeitsch. Nahr. Genussm., 1901, 4, 1123.

Take 100 c.c. of the wine, expel the volatile acids with steam as described in the method for estimating these acids, remove the residue to a porcelain basin, and neutralise the remaining acids with barium hydroxide solution, using litmus paper as indicator. Then add 5 to 10 c.c. of a 10 per cent. solution of barium chloride, evaporate the liquid to about 25 c.c, and restore the neutrality, if necessary, with a few drops of the barium hydroxide solution. Now add carefully, with constant stirring, small quantities of pure alcohol (96 per cent.) until the liquid has a volume of 70 to 80 c.c.; transfer it to a 100 c.c. flask, and make the volume up to the mark with the alcohol. Filter off 80 c.c. through a dry folded filter, add a little water to the filtrate, and evaporate it to dryness in a platinum capsule. Ignite the residue carefully, without pushing the incineration so far as to give a white ash, and determine the alkalinity of the ash with N/2- or N/4-HC1, converting the result into terms of normal alkali per 100 c.c. of the wine. One c.c. of N/1 alkali - 009 gram of lactic acid.