The dose of the acid is from two to ten drops, according to its strength. About five drops is a medium dose, which may be given in from two to four fluidounces of sweetened water, and repeated two, three, or four times in twenty-four hours. As the medicine, in large doses, is apt to induce colicky pains, it is best to begin with a small dose, and increase till it evinces some sign of acting. The same caution should be observed as with the other acids, to guard the teeth against injury. Care should be taken, in opening the bottle in which the acid may be contained, to avoid exposing the face to the jet of gaseous vapour, which sometimes suddenly escapes, especially when the bottle has been kept in a warm place, and which may endanger the eyes, if not guarded. When the patient, or a nurse, mixes the acids, particular direction should be given that they should not be dropped into water before they have been mingled, and full time has been allowed for mutual reaction. In fact, it is best that the mixture should be made by the apothecary, and, after sufficient reaction has taken place, should be diluted before being dispensed. I frequently thus prescribe the remedy, directing it to be diluted with camphor water, in such proportion that a tablespoonful of the preparation shall constitute a dose, to be afterwards further diluted by the patient. To this mixture a portion of laudanum may be added, whenever indicated.

The incompatibles are so numerous, that the safest plan is to give the acid without other accompaniments than those just mentioned. It should be administered from a wineglass, or by means of some other glass or porcelain instrument, and never from a metallic spoon, especially one of silver.

So far as concerns the effects of the medicine on the liver, it has been thought that its external use is scarcely less efficient than the internal. At least, the two methods may often be advantageously conjoined; or the outward application may be resorted to when the medicine operates offensively on the alimentary canal. It may be employed externally in the form of lotion, footbath, or full bath. For the purpose first mentioned, it may be added to water, in the proportion of two fluidrachms to a pint, and applied by means of a sponge. For a footbath, from one to two fluidounces may be used to the gallon of water; for a bath, about one fluidounce to the same quantity. Both the bath and footbath should be at the temperature of about 96° F., and should be prepared in wooden vessels. The application may be continued from ten to thirty minutes, or till a tingling or pricking sensation begins to be felt in the skin. It may be repeated daily, or twice a day.