As kept for internal use, sulphuric acid is always in one of the following forms. In relation to its external use as a caustic, it will be treated of under the escharotics.

1. Diluted Sulphuric Acid. - Acidum Sulphuricum Di-Lutum. U. S., Br

This is prepared by the U. S. Pharmacopoeia, by mixing two troy-ounces of concentrated sulphuric acid, with fourteen fluidounces of distilled water, then filtering, and passing through the filter as much more of the water, as may be necessary to make the diluted acid measure a pint, After the mixture, a white insoluble substance gradually separates, if the commercial acid is used in the preparation. It is the sulphate of lead previously contained in the strong acid, which would subside if the mixture were allowed to stand, and might be got rid of by decanting the clear liquid. In the U. S. process, it is separated by filtering. The British preparation is somewhat stronger, but not materially so. Even in this state of dilution, the acid is still corrosive, and requires to be much more diluted before it can be borne by the palate. The officinal preparation is intensely sour, and will set the teeth on edge, if it come in contact with them. When taken, therefore, it should either be sucked through a quill, or other tube introduced far into the mouth; or, what I think is ordinarily a better plan, it should be swallowed rapidly, and the mouth, immediately afterwards, well and repeatedly washed out with water, or a weak solution of one of the alkaline carbonates. Without some precaution of this kind, the teeth may be seriously injured.

The dose of the diluted acid is from ten to thirty drops, to be repeated, for ordinary purposes, three times a day, or more frequently. To be efficient in hemorrhages, it must be given every two hours. The dose should be taken in one or two wineglassfuls of water, sweetened or not, as the patient may prefer. When used as a drink in hemorrhages or fevers, the same quantity may be added to half a pint or a pint of water.

For a gargle, in ulcerative affections of the throat, a fluidrachm may be added to a pint of water; for application to the skin, double the quantity. When intended for pseudomembranous patches in the mouth or fauces, this preparation may be used undiluted, and should be applied by a brush directly to the affected part, and no other.

Compound Infusion of Roses (Infusum Rosae Compositum, U. S)is an infusion of red roses, containing about three fluidrachms of the diluted sulphuric acid in two and a half pints. The preparation acquires a slight astringency and a red colour from the roses; but its efficacy depends altogether on the acid. It is considerably used in Great Britain, as a drink in hemorrhages and colliquative sweats, and as a vehicle for saline medicines, especially sulphate of magnesia, the taste of which it in some measure conceals. The dose is from two to four fluidounces. It is also used as gargle.

2. Aromatic Sulphuric Acid. - Acidum Sulphuricum Aromaticum. U. S., Br. - Elixir Of Vitriol

This preparation, which is very generally known under the name of elixir of vitriol, is a simplification of Mynsicht's acid elixir. It is prepared, according to the present U. S. process, by obtaining a tincture of ginger and cinnamon by percolation with alcohol, and then adding the tincture to a mixture of sulphuric acid and alcohol previously prepared. It may be considered as a tincture of the aromatics mentioned mixed with the acid; though some chemical reaction has no doubt taken place between the several ingredients. It contains one part of the acid to about nine parts by measure of alcohol, and is therefore considerably stronger than the preceding preparation. As the drop, however, is smaller, the dose is about the same as given in drops. The U. S. preparation is about one-third stronger than the British. It is a reddish-brown liquid, of a peculiar agreeable odour, and, when diluted, of an acid not unpleasant taste. In this country, it is the form generally preferred for the internal administration of sulphuric acid. The dose of it is from ten to thirty drops, given in one or two wineglassfuls of water. It is very often used as an addition to sulphate of quinia to render it soluble in water; and is an ingredient in the two Infusions of Peruvian Bark of the U. S. Pharmacopoeia, in the preparation of which it enables the water to extract all the virtues of the bark, while it agreeably qualifies the taste of the infusion.

3. Ointment Of Sulphuric Acid

This ointment was until recently an officinal of the Dublin College. It was made by rubbing together a drachm of the acid and an ounce of lard. Reaction took place, which altered the colour of the ointment; but it was still merely a dilute preparation of sulphuric acid for external use. Mixed with an equal quantity of lard, it was employed as a remedy for scabies, lichenous ringworms, prurigo, and other obstinate cutaneous eruptions, and, still further diluted, as a rubefacient in paralysis, chronic inflammation of the joints, rheumatism, etc.