2. From Rock Salt

Beds of rock salt of great extent, formed by the evaporation of prehistoric seas, are found in many parts of the world. In the United States these beds occur especially in New York, Michigan, Kansas and Louisiana. They are sometimes near the surface but often at a depth of a thousand feet or more. The salt is mined by sinking a shaft and working similar to a coal mine. The rocksalt, if sufficiently pure, is sold just as mined, or gound and screened, and put upon the market directly. This product is often 98 to 99 per cent. pure.

3. By Evaporating a Brine Obtained From Salt Beds

This is one of the commonest and most satisfactory methods. A drilling is made into the salt, and lined with tubing, another tube is hung loosely in this outer tube, leaving an annular space, between the two thus (0). Fresh water is pumped into this annular space, becomes saturated with salt in the strata below, and is subsequently pumped out through the inner tube and evaporated. This evaporation is carried on by solar heat, in open pans heated directly over a fire, or heated by steam or more recently in open pans connected with an exhaust or vacuum pan. The brine be somewhat purified at first by partially concentrating in a pan where the less soluble constituents, such as calcium sulfate crystallize out, and then running into the main evaporating pan. The salt is raked out of the pans, allowed to drain, and sometimes dried artificially before it is put upon the market.

Composition

The analysis of average common salt is as follows:

may

Although there is an abundance of salt in the United States, considerable quantities are imported, especially for salting meats.

In some countries as Australia, Italy and China, the manufacture and sale of common salt in a government monopoly, and the salt is sold at a high price in order to produce revenue for the Government. In France, Germany and India, salt to be used for food is subject to a tax, and salt used for other purposes is "denatured," by the addition of some foreign material so that it shall not be fit to use for seasoning food.

Dietetic Use of Common Salt

The amount of sodium chloride taken with the food is so large that the chlorine contained in foods in the form of mineral salts, is of no importance. It is interesting to note that among animals the herbivora require salt in their food, while the carnivora do not. In discussing the natural craving for salt experienced by man and the herbivorous animals, Bunge1 (Physiological and Pathological Chemistry) explains it about as follows: "Most vegetables are rich in potassium which is ultimately eliminated in the form of mineral salts, largely as sulfate. Potassium sulfate in the blood reacts to some extent with sodium chloride forming potassium chloride and sodium sulfate, both of which are rapidly eliminated by the kidneys. Hence the greater the amount of potash in the food, the greater the loss of sodium and chlorine from the blood, and the greater the necessity for salt to keep up the normal sodium chloride content of the body." Bunge in continuing this discussion concludes that while one might live without the addition of salt to the food, even on a diet largely vegetarian, without salt he would have a disinclination to eat much of the vegetables rich in potassium, such as potatoes, so the use of salt tends to enable us to utilize a larger variety of the earth's food products. Use of excessive amounts of salt is probably injurious as it overstimulates digestion, and may overtax the organs concerned in its elimination.

1 Chemistry of Food and Nutrition, Sherman, p. 263.

CHAPTER XIX

NON-INTOXICATING BEVERAGES

From very early times man has prepared mildly stimulating non-intoxicating beverages from various vegetable substances. It is rather remarkable that people of different nationalities, living under entirely different conditions of civilization, some earlier and some later in the history of the development of the race, should have felt the necessity, or should have appreciated the satisfaction to be derived from the use of this class of beverages, and that they selected for making them plants that contained, in a general way, similar constituents.

The most important principle contained in these beverages is the alkaloid, a nitrogenous substance which has stimulating properties. Tea, coffee, and cocoa contain also a volatile oil, which gives an agreeable odor and taste to the beverage, and a considerable amount of an astringent principle related to tannin, which modifies the taste and has also a physiological action on the system. Other plants, used more generally in South America, Africa and the East Indies than in North America and Europe, are the Maté, Khât, Kola, Guarana and Coca, and these contain similar constituents.

TEA (Thea chinensis)

History

The tea plant grows in sub-tropical regions which have a rainfall of 60 inches or more. The species found growing wild in Assam and Burmah is supposed to be the progen tor of the modern tea plant. Some species still grow wild in the moun

tainous regions of China and India. The natives of China relate a legend that is supposed to account for the origin of tea. A Buddhist priest came from India to China, and as he was a devout man, he wanted to spend much time in prayer, but was hindered by the fact that he was overcome by sleep. In despair he cut off his eyelids and threw them on the ground, and the next day he found growing in the same spot the tea plant, the leaves of which furnished a beverage that would prevent sleep. Tea has been used in China for four thousand years or more.

FIG. 89.-A tea plantation in China. (By permission Chase & Sanborn.)

The tea plant was introduced into Japan in the thirteenth century1 and was imported in commercial quantities into England in 1673, although a tea-house had been established in 1657 in London. At first it sold at the rate of $50.00 per pound. Besides China, Japan, and Assam, tea is also grown in Ceylon and Java, and to some extent in Brazil. The first plantation in Ceylon was opened up in 1867, and so rapidly has the industry grown, that in 1909 over 192,000,000 pounds was raised.

1 Foods, Their Origin, Composition and Manufacture, Tibbles, p. 779.

Cultivation of the Plant

The tea plant is a small shrub, growing to the height of 3 or 4 feet if cultivated, but if allowed to grow without pruning it reaches a much greater height. (Fig. 89.) (Fig. 89.) The plants are started in the nursery from seeds, and then transplanted to the field where they are set in rows about 4 feet apart. The vigorous pruning to which the shrub is subjected causes it to send out numerous young shoots. The leaves are ready for picking in three years after the plant is started, and in some countries as India are picked as often as twenty-five times a season.1

Manufacture of Tea

There are in general two kinds of tea on the market, green and black, both made from the same stock but by different methods of treatment. Green tea is made by first drying the leaves and then heating them below the boiling point of water with constant stirring in a pan over a fire, or with steam. The next process is to roll the moist leaves into balls by hand, allow them to sweat for a short time in heaps and again roast them gently. By this process the aroma is distributed and the green color is retained. The leaves are then sifted and sorted into different grades, and again roasted. In some countries a part of this process is done by machinery.

Once more the

Black tea is made by first withering the leaves on trays in the sun then tossing them in the air until they are soft, and finally piling them in heaps in a cool place to ferment for some hours. When the fermentation is complete the leaves are heated over a fire, then rolled by hand upon a rattan table. Some of the black teas, as the Congous, are heavily fermented. leaves are exposed to the sun, and then roasted and rolled a second time. After roasting and rolling three times, the tea is sifted, dried and packed. Great skill is necessary so that the leaves be fermented and roasted enough to eliminate the raw flavor, de1 U. S. Dept. Agri. Div. Chem. Bul. 13. pt. 7.