A solution containing 10 per cent, of hydrogen chlorid. HC1.

Properties : Diluted hydrochloric acid is a colorless, odorless, strongly acid aqueous solution; freely miscible in all proportions with water or alcohol.

Incompatibilities : It is incompatible with alkalies, carbonates and oxids, with which it reacts to form chlorids, and with the soluble salts of silver and of lead, forming insoluble silver chlorid and lead chlorid.

Action and Uses: Hydrochloric acid is the acid of the gastric juice, the average normal stomach contents containing approximately 0.2 per cent. It is necessary to the digestive action of pepsin and acts as an antiseptic in the stomach. By checking fermentation and putrefaction in the stomach it tends to prevent these processes in the intestine.

Diluted hydrochloric acid is used for the treatment of diseases of the stomach characterized by a deficiency of acid in the gastric juice on the theory that it replaces the acid lacking in the secretion. To restore the acidity of the stomach contents to the normal average would require much larger doses than are commonly given. It seems probable, therefore, that the acid as ordinarily given acts mainly as an appetizer and tonic. The utility of hydrochloric acid in achylia gastrica is more manifest in the nervous forms and in the earlier stages of the organic variety. In some cases it causes distress and should be discontinued. There is some evidence to show that the continued administration of the acid is capable of increasing the gastric secretion. Hydrochloric acid also exerts a favorable influence on the secretion of the pancreatic and intestinal juices.

Hydrochloric acid is also of service in intestinal putrefaction, especially when the gastric digestion is impaired. It is indicated in achylia gastrica for the diarrhea caused by the irritant action of undigested meat and the putrefaction of proteins which have escaped gastric digestion.

Dosage: 1 c.c. or 15 minims in about half a glass of water. It should be given after meals and the dose repeated at the end of an hour. Five drops in a wineglassful of water after meals are often sufficient.