Elements in the molecular and ionic condition are very different things. In the latter state the element is atomic, and is charged with electricity. No substance is entirely resolved by solution into ions, and the degree of dissociation depends on the nature of the solution, on the temperature, and concentration; many substances such as sugar, urea, and alcohol, do not ionise, but preserve in solution the molecular condition. It is believed, therefore, that it is the ions of a salt which produce a pharmacological action, and dissociable salts containing two ions will have two different effects. As examples of this hypothesis, we may point out that acids exert their disinfectant properties in proportion to their dissociation that is to the concentration of hydrogen ions in the solution. The toxic action of metallic salts varies also with their degree of dissociation while some metallic compounds of arsenic, such as the cacodylates, which do not dissociate into an arsenious (AsO₃) or arsenic (AsO₄) ion, have not the characteristic actions of arsenic. But, besides the ionic action of salts, there is a second and physical action which is negligible so long as the ionic action is strong; this physical, or "salt," action, affects living tissues through changing the physical properties of the fluids in or surrounding them. Osmosis is the principal physical change included under salt action, and osmotic processes play an important part in facilitating the movement of fluids and the diffusion of salts in the organism. The term isotonic has come to mean a solution having the same osmotic tension as that of blood scrum, higher molecular concentrations are spoken of as hypertonic and lower as hypotonic. An isotonic solution of sodium chloride (Liquor Sodii Chloridi) contains 0.91 per cent. In the living body, however, osmotic processes, though important, are not always the deciding factor as to the action of salts, thus the ions K, Na, Li, Cl, Br, are absorbed rapidly from the intestines in any concentration, whilst Ca is absorbed more slowly, and the Mg and SO₄ ions hardly at all. A saline purgative is therefore a salt which is not capable of absorption, and which by osmosis attracts fluid from the intestinal cell-wall and renders the contents of the bowel more watery. From 5 to 12 grammes of sodium chloride is excreted daily in the urine. Neither ion has any specific action, and the salt is therefore limited to a physical action. The most important of these actions is on the kidneys, and is common to in salts which are absorbed. When salts reach the blood by absorption, the flow of urine is increased; no matter how the salts are introduced into the blood, the effect must be to increase the liquid part of the blood; this hydraemic plethora causes dilatation of the renal vessels, a greater rate of blood flow, and an increased secretion of urine. Salts also slightly increase the perspiration and the bronchial mucus. Sodium chloride is administered as an emetic, dissolved in warm water. As Liquor Sodii Chloridi it is much employed in surgical procedures and to augment the body fluids. Solution of common salt (1 in 20) is a household remedy for sprains and bruises; as a gargle and wash for the nose, Nebula Sodii Chloridi Composita is suitable. Sodium chloride is considered to be contra-indicated internally in dropsical conditions, pleurisy with effusion, and in gout and rheumatism. A salt-free diet has been used in recent times as a treatment for renal disease and dropsy. In carefully selected cases great improvement has been obtained, patients who have been dropsical for years often losing all their oedema.

Dose.—1/2 to 4 grammes (10 to 60 grains).

PREPARATIONS.

Soda Water - Glucose and Sodium Chloride Solution - Compound Alkaline Powder

Balneum Sodii Chloridi, B.P.C.—SALT BATH. 1 in 40.

For a full-sized bath use 140 litres (30 gallons) of water containing 3500 grammes (120 ounces) of sodium chloride or sea salt. Used in gout and rheumatism.

Liquor Sodii Chloridi, B.P.C.—SOLUTION OF SODIUM CHLORIDE. Syn.—Physiological Salt Solution; Isotonic Salt Solution; Solutio Salina; Normal Saline Solution.

Sodium chloride, 0.91; water, to 100. Normal saline solution is isotonic, since it has abort the same osmotic equivalent as blood serum. It is usually sterilised by boiling for at least five minutes in a flask, the neck of which is plugged with sterilised cotton wool. This solution is employed in large quantities for subcutaneous, intravenous, or rectal injection when the body has lost much fluid as in haemorrhage, acute diarrhoea, etc., also to prevent shock during prolonged operations, the injection being given at a temperature of about 40°. It is similarly employed in uraemia, diabetic coma. pneumonia and other intoxications to promote excretion of poisonous substances. It is a suitable vehicle for hypodermic injections of alkaloids, etc. Normal salute solution is employed in abdominal surgery to cleanse the peritoneal cavity. It is preferably made up with tap water which has been allowed to run for some time, and contains tracts of calcium and potassium salts. A still better solution, containing the requisite amount of calcium, potassium, and alkali, may be made according to the modified formula of Ringer, as follows:—Sodium chloride, 0.91; potassium chloride, 0.025; calcium chloride, 0.02; sodium bicarbonate, 0.015; water, sufficient to produce 100. Sea-water sterilised by filtration and diluted with distilled water until isotonic, is used as an injection in phthisis, malnutrition and other conditions.

Nebula Sodii Chloridi Composita, B.P.C.—COMPOUND SODIUM CHLORIDE SPRAY.

Sodium bicarbonate, 1.5; sodium chloride, 0.75; borax, 1.5; distilled water, to 100. Used as a soothing spray for the throat and nose, or as a nasal irrigation in chronic eustachian and nasal catarrh.

Solvellae Sodii Chloridi, B.P.C.—SOLUBLE SODIUM CHLORIDE TABLETS. 15 grains.

One tablet dissolved in 150 mils (5 fluid ounces) of recently boiled and cooled tap-water will produce an extemporaneous normal saline solution.

The British Pharmaceutical Codex, 1911, was published by direction of the Council of the Pharmaceutical Society of Great Britain.