MALIC ACID
Leach’s Method.—To 5 cc. of the sample, add a few drops of a solution of calcium chlorid (1 : 10); make slightly alkaline with ammonia. Filter off any precipitate that may form, add 20 to 30 cc. of 95 per cent alcohol to the filtrate and heat to boiling. If malic acid is present, a voluminous flocculent precipitate will form. A precipitate may form in vinegars containing dextrine. Make a further test for malic acid by the following: Filter and treat the precipitate with a little alcohol, and when dry add concentrated nitric acid and evaporate to dryness on a water-bath. Treat the residue with sodium carbonate, boil for a short time, filter. Add acetic acid to the filtrate till slightly alkaline, boil till carbon dioxid is expelled, and if on the addition of calcium sulfate a precipitate forms, it indicates the presence of malic acid.