The liquids mostly employed in the cooking of foods are water and milk.  Water is best suited for the cooking of most foods, but for such farinaceous foods as rice, macaroni, and farina, milk, or at least part milk, is preferable, as it adds to their nutritive value.  In using milk for cooking purposes, it should be remembered that being more dense than water, when heated, less steam escapes, and consequently it boils sooner than does water.  Then, too, milk being more dense, when it is used alone for cooking, a little larger quantity of fluid will be required than when water is used.

The boiling point for water at the sea level is 212 deg.  At all points above the sea level, water boils at a temperature below 212 deg., the exact temperature depending upon the altitude.  At the top of Mt.  Blanc, an altitude of 15,000 feet, water boils at 185 deg.  The boiling point is lowered one degree for every 600 feet increase in altitude.  The boiling point may be increased by adding soluble substances to the water.  A saturated solution of common baking soda boils at 220 deg.  A saturated solution of chloride of sodium boils at 227 deg.  A similar solution of sal-ammoniac boils at 238 deg.  Of course such solutions cannot be used advantageously, except as a means of cooking articles placed in hermetically sealed vessels and immersed in the liquid.

Different effects upon food are produced by the use of hard and soft water.  Peas and beans boiled in hard water containing lime or gypsum, will not become tender, because these chemical substances harden vegetable casein, of which element peas and beans are largely composed.  For extracting the juices of meat and the soluble parts of other foods, soft water is best, as it more readily penetrates the tissue; but when it is desired to preserve the articles whole, and retain their juices and flavors, hard water is preferable.

Foods should be put to cook in cold or boiling water, in accordance with the object to be attained in their cooking.  Foods from which it is desirable to extract the nutrient properties, as for broths, extracts, etc., should be put to cook in cold water.  Foods to be kept intact as nearly as may be, should be put to cook in boiling water.

Hot and cold water act differently upon the different food elements.  Starch is but slightly acted upon by cold water.  When starch is added to several times its bulk of hot water, all the starch granules burst on approaching the boiling point, and swell to such a degree as to occupy nearly the whole volume of the water, forming a pasty mess.  Sugar is dissolved readily in the either hot or cold water.  Cold water extracts albumen.  Hot water coagulates it.