The uses of ice.—Water freezes and ice melts at the same point, 32° F., or 0° C. If ice is mixed with salt, the temperature is reduced far below the freezing point, nearly to 0° F. This process reduces any watery substance which it surrounds to its freezing point, the heat being used in the melting of the ice. This is an interesting topic to discuss in the Physics class.
Ice at its ordinary temperature of 32° F. is used for cooling food agreeably. Its most important function in the refrigerator is as preserver of food for a short time at least. For this it is invaluable, and cheap ice is really necessary in summer to the health of a great city.
Ice substitutes.—Where the supply fails or the price is exorbitant, one property of water makes it a partial aid.
The rapid evaporation of water will absorb heat so rapidly as to reduce the temperature of adjacent bodies. In the tropics when ice is lacking, water is hung in porous jars in the breeze, and the temperature of the water in the jar is reduced.
To keep milk and butter cool wrap a wet cloth about the containing jar, and set the jar upon the window sill, keeping one end of the towel in a vessel of water; or the cloth may be wrapped directly around the butter. This method is surprisingly effective.
Fruit beverages.—Fruit juices with water and sugar make refreshing beverages and have nutritive value as well. (See the next chapter.)
Cocoa and chocolate, coffee, and tea.—These are the three most important non-alcoholic beverages used by man. They are used because of the agreeable flavor given them by volatile oils, and also because they have a stimulating effect. The stimulating property is due to an alkaloid, a crystallizable substance known in cocoa as theobromine, in coffee as caffeine, and in tea as theine. Chemical investigation indicates that caffeine and theine are the same and theobromine is a closely related substance. These substances have a recognized stimulating effect upon the nervous system, and the beverages containing them should therefore be used with caution by all. In the opinion of the writers, tea and coffee should not be taken by young people under twenty-five years of age. Tea and coffee also contain tannin, an astringent substance giving a disagreeable flavor to coffee and tea when these are improperly made, and having an undesirable effect upon digestion. Chocolate contains a non-volatile fat (cocoa butter) in large amount, and should be classed as a food as well as a beverage.
The plants from which cocoa, coffee, and tea are derived are natives of semi-tropical or tropical Africa, Asia, and
America, having been introduced to Europe by early travelers in these lands.
The introduction of these beverages is an interesting bit of history. The Spaniards found cocoa in tropical America, and carried it back to Spain, and it was not used in England until 1657. It was sold in Danvers, Massachusetts, in 1771, the raw material having been brought by Gloucester fishermen from the West Indies. Coffee is said to have originated in Abyssinia, reaching Europe by way of Arabia, and being sold in England in 1650. Coffee-houses were licensed in America in 1715. A Chinese tradition places the discovery of the use of tea at 2700 B.C. It was first used in England in 1657, and was imported into America in 1711. An amusing story is told of the first tea party in a town of western Connecticut, where the tea was boiled violently in a large iron kettle and served on a platter with the leaves, as a form of soup, the leaves themselves being eaten.