Page:Popular Science Monthly Volume 30.djvu/398

382 lead (litharge) should never be used, but salt-glazed ware is safe. Vinegar is rarely adulterated with sulphuric acid; and oxalic acid, which is a violent poison, has also been found in it. According to the "United States Dispensatory," if vinegar is evaporated in contact with white sugar, or on white paper, the presence of free sulphuric acid will be indicated by charring. Such acrid substances as red pepper and mustard are sometimes added to vinegar to increase its apparent sharpness. They may be detected by their biting taste after evaporating a portion of the vinegar to a small bulk. Consumers need have little fear of adulterations, however, if their vinegar comes from ordinarily reputable dealers; besides, genuine vinegar can be made more cheaply than any passable imitation. There is more chance of unwholesome vinegar coming into the household in pickles and catchups than when the vinegar is bought alone.

By distillation vinegar is deprived of its coloring and other non-volatile matters. The product is always weaker than the vinegar from which it is derived, as the boiling-point of strong acetic acid is above that of water, and it contains small quantities of alcohol and empyreumatic bodies formed during the operation. Distilled vinegar was formerly used in pharmacy, but dilute acetic acid has now taken its place.

The acetic acid used in the arts is not obtained from the acetification of alcoholic liquors, but from the destructive distillation of wood, generally in the form of sawdust. It is called commercially pyroligne, ous acid, or wood-vinegar, and contains as impurities tar, wood-spirit-etc, which give it an empyreumatic or smoky odor, and which make it superior to other vinegar for preserving meats, pickles, etc. It is purified, and with the addition of coloring and flavoring matters has been sold for culinary use. As the complete purification is an expensive process, there is danger that this vinegar, if sold at a low price, will contain unwholesome substances.

The value of vinegar as a condiment depends on the fact that acetic acid dissolves gelatin, fibrin, and albumen; hence it aids in digesting young meats, fish, lobsters, and hard-boiled eggs. The acid assists also in the conversion of cellulose into sugar, which is the first stage in the digestion of the green leaves used in salads. It is a mistake to use vinegar on beans, for it renders insoluble the legumin, which is their chief nutritive constituent. Oil, pepper, mustard, and a little white wine make the best dressing for beans. It has been proved that some vegetable acid is necessary for the preservation of health, as long continuance in a diet lacking such acids produces scurvy. Vinegar will partly supply this lack, but not wholly, for it will not prevent or cure scurvy, A craving for acid is better satisfied by fruit or acid vegetables. Those young girls who indulge largely in such indigestible articles as pickled limes, cucumbers, etc., would enjoy better health if they should eat instead sour apples, tomatoes,