Characters. - In small white crystalline grains, or transparent cubic crystals, free from moisture. It has a purely saline taste, and imparts a yellow colour to flame.

Solubility and Reactions. - Is soluble in water. The solution gives the reaction of a chloride (p. 594), and does not give that of potassium but of sodium (p. 617).

Prepabations in which Chloride of Sodium is used. Acidum Hydrochloricum. Hydrargyri Perchloridum.

Hydrargyri Subchloridum.

Actions. - Although chloride of sodium is not much used as a remedy, it is most important as a food. It forms a large proportion of the salts of the body, and no doubt plays a very important part in tissue-change. When persons are deprived of it for a length of time the longing for it becomes intense, and animals will go very great distances to obtain it. When mixed with water, in the proportion of 0.65 to 100, the solution does not destroy animal tissues like water alone, and may be mixed with blood without destroying the corpuscles (vide p. 600). Strong solutions, however, are intensely irritating. When injected into the lymph-sac of a frog it causes increased diapedesis of the red corpuscles, which then pass out through the vessels in considerable numbers. It is possible that an increase in the proportion of sodium chloride may have something to do with the production of scurvy, as this disease appears to be relieved by salts containing another base than sodium and another acid radical than chlorine.

Uses. - Externally it is used as a stimulant to the skin in the form of baths (pp. 459 and 469). A solution of salt of 1/2 to 1 per cent. has been recommended by Kuhne to wash wounds and raw surfaces in place of water, as it does not destroy the vitality of the tissues, and a similar solution may be used instead of water to wash out the nasal cavities, either alone or mixed with other medicaments. When taken in considerable quantities it produces vomiting, and may be used as an emetic, either alone or to aid the action of other emetics. Half a tea-spoonful of dry salt, repeated until nausea is produced, is said sometimes to arrest haemoptysis. It appears to diminish the secretion of mucus, and may be given to children suffering from worms, where the intestinal mucus is excessive and affords a nidus for the parasites.

A solution (3SS in Sodii Chloridum B and U S P Chloride of Sodium Com 218 j water) flavoured with liquorice, in table-spoonful doses every two hours, sometimes proves very useful in causing absorption of pleuritic serous exudation. It is contra-indicated when the exudation is purulent.

After haemorrhage there is generally excessive thirst, and the addition of chloride of sodium to the water drunk by the patient has been recommended in order to prevent destruction of the blood-corpuscles which might arise from the absorption of small amounts of pure water. During convalescence patients sometimes exhibit a desire for salt and indigestible food, which, if given, would probably derange the digestion, but the craving may be allayed by giving salt alone. It has been used in bilious diarrhoea, in doses of 10 to 60 grains, three or four times a day.

As an enema to destroy ascarides it is frequently used. The proportion generally is 1 or 2 tablespoonfuls to the pint of water.