Not much need be said of the use of the mineral acids in affections of the mouth and throat. Formerly they were much employed in the treatment of mercurial and other forms of stomatitis, diphtheria, aphthae, gangrene, etc.

In using mineral acids in affections of the mouth, it should not be forgotten that they attack the enamel of the teeth. First, the animal matter adherent to the teeth is dissolved off, when the teeth are said to be "]set on edge." The acid should be applied to the affected surface only, and the mouth should afterward be washed out with an alkaline lotion. Pure hydrochloric acid may be applied with a camel's-hair brush or on a bit of soft pine-wood to the gums in cases of sloughing from mercurial stomatitis, and to the ulcers of stomatitis materna, to syphilitic mucous patches, and to those painful ulcers of the mouth which occur periodically in some subjects affected with a peculiar form of indigestion. In the case of ulcers having their origin in stomach-disorder, the internal use of hydrochloric, nitric, or nitro-hydrochloric acid, is often extremely beneficial.

The local use of hydrochloric acid in diphtheria, so strongly urged by Bretonneau, is now rarely employed, for it is well known that the diphtheritic exudation will rapidly extend over an inflamed surface produced by the application of the acid, and the destruction of the exudation at one part does not prevent its extension and renewed formation.

Any of the mineral acids administered by the stomach should be well diluted, and to prevent injury to the teeth should be taken through a glass tube or a straw. The mouth should also be rinsed out after swallowing the acid.

The mineral acids are highly useful in certain stomach-diseases. In atonic dyspepsia hydrochloric acid should be given after meals, or better, lactic acid. It is highly probable that hydrochloric acid is produced during digestion by the reaction between chloride of sodium and lactic acid. A combination of the acid with pepsin, as already suggested, is preferable in these cases of atonic dyspepsia. When, in consequence of faulty digestion, acetic, lactic, and butyric acids are produced in the stomach from the starchy, saccharine, and fatty constituents of the food, the acids given after meals add to the distress of the patient.

To prevent the excessive formation of acid, whether due to the action of the gastric glands, or to abnormal fermentation of the starchy, saccharine, and fatty elements of the food, mineral acids are used with decided advantage, but they must be administered before meals. For this purpose, hydrochloric or phosphoric acid is to be preferred. The excessive production of acid is manifested by acid eructations, pyrosis, heartburn, and ulcerative stomatitis.

Indigestion characterized by eructations of offensive gas, a sallow complexion, by the appearance of oxalate-of-lime crystals in the urine, accompanied by mental despondency, is relieved by nitro-muriatic acid; better by nitric, when the symptoms of lithaemia are predominant.

The experience of English physicians practicing in India has been favorable to the use of nitro-muriatic acid in chronic hepatic affections, and in dysentery and dropsy of hepatic origin. Acute diseases of the liver, and such chronic affections as cirrhosis and waxy degeneration, are not as a rule benefited by the mineral acids. Mucous duodenitis and catarrh of the gall-ducts accompanied by jaundice, and jaundice of malarial origin, are forms of hepatic disease in which nitro-muriatic acid is serviceable. With the internal use of the acid should be conjoined the local use to the right hypochondrium of the acid-bath. Three ounces of nitro-muriatic acid to a gallon of water is a suitable strength for the topical use in this way. The feet may be placed in the 10 bath, and the legs, arms, and abdomen may be alternately sponged, when the skin is torpid and its secretion defective. The temperature of the bath should be about 96° Fahr. (Martin). Another mode of making topical application of the acid bath is as follows: "Let a flannel roller of ten or twelve inches wide, and sufficient to encircle the body twice, be soaked in the fluid and then wrung so as to remain only damp. Apply this instantly to the body, covering it with a piece of oiled-silk to avoid damping the dress. It should be worn constantly, but should be changed, soaked, and wrung, morning and evening" (Squire). This is a very effective local application in the hepatic disorders mentioned above as amenable to treatment by the mineral acids, and is serviceable in the first stage of cirrhosis. Dr. Scott, of Bombay, ascribes to the acid bath the power to relieve the pain of hepatic colic, by causing the expulsion of the impacted calculus.

The mineral acids are very effective remedies in the treatment of summer and colliquative diarrhoea. Crapulous diarrhoea and dysentery are not benefited by them. The indications for their use are these: painless, watery evacuations, of a light color, alkaline in reaction. Hope's mixture, which contains nitrous acid, has long been used with success in such cases. The formula is as follows: Rx Acidi nitrosi, 3 j ; tincturae opii, gtt. xl; aquae camphorae, oz viij. S.: One fourth to be taken every three or four hours. A mixture of this kind may readily be extemporized, in which the relative proportion of the acid and opium may be arranged according to the indications of the case. Sulphuric acid is more decidedly astringent than nitric and muriatic, and is therefore, as a rule, to be preferred in diarrhoea. Bence Jones places them as regards their actions thus: Hydrochloric more promotes digestion; nitric acid, secretion; and sulphuric, astringency. Nitric and nitro-hydrochloric are, according to this view, better suited to stomach and hepatic disorders characterized by deficient secretion, and sulphuric is more appropriate for the relief of a relaxed state of the mucous membrane. A combination of aromatic sulphuric acid with opium is one of the most effective remedies we possess in the treatment of summer diarrhoea and cholera. Sulphuric acid may also be used with advantage in the treatment of dysentery, in combination with sulphate of magnesia. Rx Magnesii sulphat., oz j; acidi sulphur, dil., 3 ij; morphinae sulph., gr. j; aquae, oz iv. M. S.: A tablespoonful every three or four hours. After the action of a saline laxative, Hope's mixture, or an extemporized prescription of a similar kind, may be used. When the mineral acids do not quickly improve the discharges and lessen their frequency, and when they increase the tormina and tenesmus, they should be suspended. In the treatment of cholera, dilute or aromatic sulphuric acid may be given frequently, well diluted, in full doses. Opium can be added at such intervals as may be indicated. MacCormac has found the acid to be a most valuable prophylactic against cholera attacks. It should be administered with promptness when the preliminary diarrhoea is threatened.

Mineral acids, especially the muriatic, are very serviceable in fevers. They were formerly classed as refrigerants, or cooling medicines, and were supposed to allay thirst and to diminish fever. Although these notions are no longer entertained, the acids are known to render an important service in fevers. They increase secretion of the mucous membrane, and thus relieve the dryness of the tongue and fauces. As in fevers the gastric juice is deficient in acids, digestion is materially aided by their administration. In typhoid fever, the acids restrain somewhat the exhausting diarrhoea, increase the digestive power, remove or diminish the dryness of the tongue, and, it may be, destroy the microbes, which constitute the poison of typhoid, or which produce it under circumstances favorable to their development. Hydrochloric acid is preferable in the treatment of fevers. It may often be advantageously administered in beef-juice.

In scarlet fever, hydrochloric acid is frequently combined with chlorate of potassa (producing euchlorine), but it is better administered alone in this disease. Besides the internal administration of the acid, it is often mixed with water and used as a gargle, or mixed with honey and applied with a brush to the throat. One part of acid to five parts of honey or ten of water is a strong enough solution for this purpose. In the other eruptive fevers, hydrochloric acid is serviceable to allay thirst, to increase digestion, and to obviate the tendency to adynamia in these diseases. To children, the dilute hydrochloric acid may be readily administered in lemonade or in sirup of lemons.

There is no doubt of the value of the acids, especially the nitro-muriatic, in the treatment of constitutional syphilis. This remedy is not to be compared in efficiency with mercury and iodide of potassium, but in chronic cases saturated, so to speak, with these approved remedies, in which syphilitic patches persistently reappear in the mouth, nitro-muriatic acid often renders important service. It is undoubtedly true that constitutional syphilis has been treated successfully by the acids alone, but a very rigidly abstemious dietary has been enforced in these cases. It has already been shown that the denutrition method is of itself sufficient in some cases to relieve the organism of constitutional infection. How much of the result is to be ascribed to the remedy, and how much to denutrition, is not clear.

Nitric acid has been used with success in the treatment of intermittent fever by Hammond, Bailey, and others. In order to obtain a curative effect, it is necessary to give the acid in full doses every four or six hours. This acid is of great service, also, after an arrest of the paroxysms of intermittent by quinine, to remove the hepatic congestion and the changes in the glandular apparatus of the intestines induced by the fever-movement. It may be advantageously combined with the bitters, or used instead of the aromatic sulphuric acid in the preparation of the official infusum cinchonae flavae.

The mineral acids have long been used with more or less advantage in the treatment of phthisis. Their utility obviously depends on the fact that they supply to the digestive fluids a material in which they are deficient in this disease. As Fenwick has shown, both pepsin and acid occur in quantity much less than normal in the gastric juice of phthisical subjects. The acid best suited for the treatment of the indigestion of phthisis is the official acidum mu-riaticum dilutum.

Nitric acid is one of the numerous remedies used in whooping-cough. It is frequently successful in shortening the duration of the disease and moderating its violence; but it acts much more beneficially after the subsidence of the catarrhal stage. It should be given well diluted in sweetened water. Chronic bronchitis and hoarseness produced by singing and by simple acute catarrh are relieved by ten-minim doses of dilute nitric acid.

The mineral acids, especially the hydrochloric, have lately been proposed as remedies for acute rheumatism. The unquestionable utility of the tincture of the chloride of iron in rheumatism lends support to this practice. It is highly probable that the mineral acids check the formation of lactic acid in the blood. Whatever may be the nature of the action, good results from the treatment have been reported (Dr. J. James Ridge).

Some of the accidents due to lead are prevented, and relieved when they occur, by sulphuric acid. Sulphuric-acid lemonade is used by workmen in lead-factories to prevent lead-poisoning. This is supposed to act by forming the insoluble sulphate of lead. Dilute sulphuric acid is also effective in the treatment of lead-colic. The constipation due to lead is relieved by a combination of sulphuric acid and sulphate of magnesia, and the lead-cachexia is much benefited by a prescription of sulphate of quinine, sulphate of iron, and dilute sulphuric acid. The effects of lead on the nervous system are not removed by sulphuric acid.

Sulphuric acid is sometimes very effective in uterine hemorrhage. It has seemed to the author to be more useful in the case of haemorrhage due to fibroid or polypus than the flow arising from other causes. Although sometimes prescribed for pulmonary haemorrhage, it is not equal to other remedies. In intestinal haemorrhage sulphuric acid acts directly in part, and is therefore serviceable. In purpura it sometimes acts happily.

The aromatic sulphuric acid has long been used to check profuse sweating, especially the sweating of phthisis. It is certainly serviceable in this condition, but objectionable because of the ill effects of the acid on the function of digestion. If used at all, it should not in any case be long continued.

Nitric and nitro-hydrochloric acids have also been used with advantage in such diseases of the skin as lepra, impetigo, acne, erythema nodosum; and sulphuric, internally and locally, is said to be very effective in lichen, prurigo, and itching conditions in general.

In certain morbid states of the urine, as the phosphatic diathesis, oxaluria, alkalinity of the urine from disease of the urinary mucous membrane, and phosphatic calculus, the mineral acids render important service. In chronic cystitis and phosphatic deposits, a very weak solution of nitric acid (gtt. j— oz j) may be injected with advantage. In using such injections it is to be remembered that the bladder is extremely intolerant, and hence they should be permitted to escape immediately. When uric acid is in excess in the urine from faulty digestion and assimilation, nitric acid is often of great service: the excess of uric acid disappears because the foods are more perfectly prepared for admission into the blood.