There are four natural sources of the official salts of soda and their preparations, viz.:

1. Sodium, a metallic element.

2. Sodium chloride, or common salt, obtained from sea-water by evaporation and from salt mines.

3. Sodium nitrate. Found native in Chili and purified by crystallization from water.

4. Sodium borate or borax; a native product found in various localities.

Physiological Actions

The salts of soda are absorbed into the blood and excreted from it more slowly than the salts of potash, and for this reason the action of soda upon the alimentary canal is stronger than that of potash. It is diuretic, but not as strongly so as potash; antacid, and purgative. It is less depressing than potash and more easily borne by the stomach. The soda salts are taken into the organism in large quantities with food, especially vegetables and fruits, and are the chief source of the natural alkalinity of the blood. Soda is excreted by all the mucous surfaces, by the kidneys, the liver, and, possibly, by the skin.

Sodii Chloridum. Sodium Chloride. (Common Salt.)

Salt performs a very important part in the human economy. It exists normally in the blood in the proportion of 9 to 1000, and is very abundant in various normal secretions. Active tissue changes are promoted by the presence of salt. It stimulates the desire for food, and aids in its thorough alteration and absorption. It is the natural antiseptic of the blood; aids osmosis,1 and keeps the fibrin and albumin of the blood in solution. Water alone is injurious to cut tissues, but a weak solution of salt makes it non-irritant. During the course of an inflammation sodium chloride, being needed for its solvent action, accumulates in the inflamed area, disappearing temporarily from the urine. This is notably the case in pneumonia, and the return of the chloride to the urine marks a favorable change in the condition of the patient. In substance or in strong solution it is irritating to cut surfaces, mucous membranes, muscle and nerve tissue. Taken into the stomach in large quantities it causes vomiting, and when absorbed in excess of the needs of the system it causes the nervous irritation which produces the sensation of thirst, and which is relieved by taking enough water to dissolve the salt and carry it away to be excreted by the kidneys. Salt dissolves in 2 3/4 parts of water.

1The force by which fluids pass through moist membranes.

In convalescence patients often crave some salty article of food which, being indigestible, must be denied them, but the need of the system which is thus expressed, may be satisfied by giving salt in another way.

The difficulty found by some persons in digesting milk may possibly be overcome or lessened by adding a generous pinch of salt to the beverage.

Salt water in strong solution is an anthelmintic.