Whiskey may thus be converted into vinegar in twentyfour hours.

Cider is also used to a considerable extent, in the United States, for the manufacture of vinegar. In former years, most of it was derived from this source. The cider is left for a longer time (from eight to ten months) in half-filled casks, the bungs being left out to allow the free entrance of air. The flavor of cider vinegar is peculiar, and is much preferred by many people.

Proof vinegar contains about five per cent of acetic acid, but that sold in the shops often contains only three per cent, or even less. Because of the high price of vinegar, it has frequently been adulterated with other acids, such as sulphuric, muriatic, and rarely with nitric. They may be detected as follows. To one portion of the suspected vinegar add a few drops of barium chloride. Only a slight cloudiness should appear, but any considerable precipitate will show the presence of an undue amount of sulphuric acid. Hydrochloric acid is shown by the addition of a few drops of silver nitrate to a fresh portion of the sample. A white flocculent precipitate will appear if there has been an addition of hydrochloric acid. For the relative strength of a num

ber of samples, if the apparatus for volumetric analysis is at hand, the quantity of soda which the same number of cubic centimetres will neutralize, will give an approximate test, but not exact, because acetate of sodium has itself a slight alkaline reaction. With baryta water (barium hydrate) as the alkali, and tumeric as the test paper, the method gives very close results.

For ketchups, sauces, and pickles which are prepared with vinegar, pure vinegar should be used. In the case of pickles, a depraved taste has led to the demand for bright green pickles, and this taste has sometimes been gratified by boiling the pickles in copper kettles with vinegar and a little alum. The acetic acid of the vinegar acts upon the copper, forming a little acetate of copper, one of the most poisonous of all the salts of copper; and this, being absorbed by the pickles, colors them green. Cheap pickles are put up in adulterated vinegar. The tests are the same as those given above. For the presence of copper, immerse a strip of clean bright iron in the liquid, and, if copper is present, the iron will become coated with a thin film of metallic copper.

SALT.

Salt is of universal use, and it has been known from the earliest times. It is found in a solid rock-like form in many countries. Salt springs are not uncommon, and on the coast the evaporation of sea-water gives sea-salt. Rock-salt is mined in Austria and at North

wick, near Liverpool, in England. A mine is now worked in Louisiana. Much salt is made in New York, Michigan, Ohio, Virginia, and West Virginia, by evaporating the water of salt springs. Salt is nearly pure sodium chloride, but it almost always contains small quantities of chloride of magnesium, which causes the salt to become moist in damp air, and which gives t it the bitter taste often noticed.

There is a difference of opinion as to the healthfulness of salt when taken with food. Habit, rather than common sense, seems to govern the amount used.

VIII.

PERISHABLE FOODS, AND THE MEANS FOR PRESERVING THEM.

MEAT, FISH, ETC.

INCE butcher's meat is not liable to adulteration,

SINCE

properly speaking, any extended discussion of its character would be out of place in this little volume. Yet it cannot be passed by without a word, for it is a form of food which requires very little expenditure of force for its assimilation, since that work was done by the animal when living, and man avails himself of it. Rightly used, it forms a valuable addition to man's diet. The consumption of meat has steadily increased, in spite of the increase in price. It is said that the cost of meat in England has increased thirty-five per cent in the past twenty-two years. A large quantity of dried and tinned meat is now exported from Australia and South America.

The amount consumed in different countries varies from about one tenth of a pound a day, or one pound

in ten days, in Russia and Spain, one pound in three days in England, one in two days in New York, to a pound a day in Buenos Ayres and Uruguay, where animals are killed for their hides and horns. Meat should be obtained from healthy animals, and kept in a clean place, in order that it may form a wholesome food. The bad odor of tainted meat should be a sufficient warning of its character. A very slight taint, such as sometimes occurs on the outer edges, may be corrected by placing some charcoal in the water in which it is boiling. In order to kill all parasites, meat should be thoroughly cooked; and for this, boiling is safer than roasting. A general average composition may be shown by the following mean of many analyses :

Fish seems to be somewhat less digestible than meat, possibly on account of the little blood in the tissue. The average composition is: mineral matter, one to two per cent; nitrogenous substance, ten to twenty; fat, five to ten; water, seventy to eighty per

cent.