External

It is, if concentrated, a powerful irritant and caustic, acting by abstracting water from the part to which it is applied. It dissolves fatty matters that may be present on the surface. It is antacid, and, if freely diluted, sedative.

Internal

Mouth. - As alkalies check alkaline secretions, potash momentarily checks the secretion of saliva.

Stomach

Because alkalies stimulate acid secretions, the flow of gastric juice is excited, if alkalies are given before a meal, but if at the end of or after a meal the gastric juice already secreted is neutralized. Being readily diffusible, alkalies are quickly absorbed.

Blood

This is rendered more alkaline. Probably all alkalies circulate in the blood as carbonates, but their action as alkalizers of the blood is very transitory, for they are quickly excreted. The amount of haemoglobin, if it is deficient, is said to be increased. The continual use of alkalies diminishes the quantity of fat.

Heart

Large amounts of potassium salts are depressant to all muscular tissues, and therefore decrease the force of the heart, ultimately causing diastolic arrest by direct action on the cardiac muscle.

Kidney

Potassium salts are diuretic, acting directly on the renal epithelium. They are quickly excreted in the urine, rendering it alkaline, and thus increasing its power of holding uric acid in solution.

Respiratory Passages

The bronchial secretion is increased in quantity, and it is rendered less viscid, but in some cases of bronchitis it is diminished.

Muscle

The prolonged contraction produced by veratrine, or barium salts, is abolished by potassium salts. They are direct muscular depressants, and depress also the nervous system, especially the brain and spinal cord.

Metabolism

Potassium salts, like all alkalies, if given in large doses, increase metabolism, leading to a greater oxidation of proteids and fats.

Therapeutics of Potash

External

Caustic potash is used to destroy lupus, and it was formerly employed to make issues. Care must be taken to limit its action, for it diffuses very rapidly. Liquor potassae is used to dissolve off the fatty matters and thoroughly cleanse the skin before operations, and weaker solutions of it are employed to remove the epidermis in certain chronic skin diseases. A 40 per cent. solution is recommended to remove an ingrowing toenail, which is painted with the fluid, and in a few seconds is so softened that much can be scraped off. The procedure is repeated till the nail that remains is sufficiently thin to be removed with a pair of fine scissors. Dilute solutions, acting as sedatives, relieve itching.

Internal

To obtain the effects of alkalies upon internal organs, potassium bicarbonate, citrate and acetate are preferable to potash, for that is apt to irritate the stomach; but it is occasionally used in small doses as a gastric sedative for dyspepsia.

Toxicology

See Soda, p. 139.