School and Home Cooking

by Carlotta C. Greer

WATER AND BEVERAGES (A)

EXPERIMENT 6: THE DISSOLVING POWER OF WATER.—Put 1/2 teaspoonful of salt in a test tube, half fill it with water. Cover the mouth of the test tube with the thumb, then shake the tube. Do the contents become clear? Set the tube aside for a few minutes. Does the salt separate from the water?

When a solid substance, by mixing with water, disappears in the water and does not separate on standing, the solid substance is dissolved. The salt was therefore dissolved in cold water, or it may be said that salt is soluble in cold water, or that water is a solvent of salt.

SOLUTION AND DIGESTION.—The change of foods in the body from insoluble to a soluble form is one step in digestion. Foods are dissolved in the digestive juices of the mouth, stomach, and intestines. Some foods such as salt and certain sugars are readily dissolved. Other foods have to undergo changes before they will dissolve. Corn-starch, for example, does not dissolve in cold water. It must be changed into sugar (which is easily dissolved) in the process of digestion. Dissolving then is an important step in the process of digesting.

USE OF WATER IN THE BODY.—A person might live for a number of weeks without eating food, but he could live only a few days without drinking water. Water has many uses in the body.

(a) It is the greatest known solvent. Because of this property, water is extremely important in the processes of digestion. (See Solution and Digestion.)

(b) It is a great carrier. Water helps carry food materials to all parts of the body; and it aids in carrying off the wastes of the body.

(c) It assists in regulating the temperature of the body. Because water is present in blood, and blood flows from the warmer interior of the body to the colder exterior, the water aids in distributing the heat of the body. The evaporation of perspiration, which is largely composed of water, also aids in regulating body temperature.

It is thus readily seen that water is needed to keep the machinery of the body working smoothly. The uses of water may be summed up in the statement: Water aids in regulating body processes.

FOREIGN MATERIALS IN WATER.—Since water is such a ready solvent, it contains many foreign materials. In passing through the air and in flowing through the ground, it dissolves many substances. Some of these substances are harmless, while some contain disease bacteria and are dangerous. Well water is frequently contaminated. It is often not safe to use for drinking purposes unless boiled.