Читать книгу The Boston cooking-school cook book онлайн
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Water is a transparent, odorless, tasteless liquid. It is derived from five sources,—rains, rivers, surface-water or shallow wells, deep wells, and springs. Water is never found pure in nature; it is nearly pure when gathered in an open field, after a heavy rainfall, or from springs. For town and city supply, surface-water is furnished by some adjacent pond or lake. Samples of such water are carefully and frequently analyzed, to make sure that it is not polluted with disease germs.
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Water freezes at a temperature of 32° F., boils at 212° F.; when bubbles appear on the surface and burst, the boiling-point is reached. In high altitudes water boils at a lower temperature. From 32° to 65° F. water is termed cold; from 65° to 92° F., tepid; 92° to 100° F., warm; over that temperature, hot. Boiled water is freed from all organic impurities, and salts of lime are precipitated: it does not ferment, and is a valuable antiseptic. Hot water is more stimulating than cold, and is of use taken on an empty stomach, while at a temperature of from 60° to 95° F. it is used as an emetic; 90° F. being the most favorable temperature.