Crampton and Simons’ Method.—Shake well together in a corked flask 50 cc. of the vinegar with about half as many grams of fullers’ earth; after standing for half an hour filter. Vinegar containing no artificial color will show scarcely any change in color when thus treated. A caramel-colored vinegar will be decolorized in proportion to the amount of caramel present.
Coal-Tar Colors in Wine Vinegar
Test by the usual test for coal-tar dyes. See under canned vegetables.
METALLIC IMPURITIES
Vinegars containing free mineral acids are sometimes found to contain poisonous metals.
Evaporate 200 to 400 cc. of the vinegar to dryness, add a little sodium hydroxid to this residue and burn to an ash over a low flame. It may be necessary to add a little potassium nitrate once or twice. Add a little dilute hydrochloric acid and saturate with hydrogen sulfid and test for lead, zinc, copper, and arsenic according to [Allen’s method] given under canned meats.
Spices to Increase Pungency
Leach.—Neutralize a portion of the vinegar with sodium carbonate. The presence of spices is easily detected by tasting this mixture.
Another Test.—Exactly neutralize a little of the vinegar as above, evaporate to smaller bulk and taste as before, then shake the concentrated liquid with ether, separate the ethereal layer and evaporate it, and taste the residue.