382 THE POPULAR SCIENCE MONTHLY. 



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 con- 

 tact with white sugar, or on white paper, the presence of free sulphuric 

 acid will be indicated by charring. Such acrid substances as red pep- 

 per and mustard are sometimes added to vinegar to increase its ap- 

 parent 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 acetifica- 

 tion 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 expen- 

 sive 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 di- 

 gesting young meats, fish, lobsters, and hard-boiled eggs. The acid 

 assists also in the conversion of cellulose into sugar, which is the first 

 6tage in the digestion of the green leaves used in salads. It is a mis- 

 take 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, 



