Acidum Arseniosum

When medicines are given in doses of a fraction of a grain the dispenser has to consider whether they are very soluble in any inert solvent which will not prevent them being made into a mass, for if they are of this nature it is obviously advantageous to dissolve, add a powder, and a suitable paste excipient to mass. Arsenious acid is not one of those substances, therefore before attempting to mass it it must be well triturated with any powders prescribed along with it. For example, in the familiar Asiatic pill, the arsenious acid is combined with ten times its weight of powdered black pepper, the resulting pill containing 1/16 grain of the acid. Here we take the prescribed amount of arsenious acid and triturate intimately in the mortar with its own bulk of the pepper, then as much again, and so on until all the pepper is used up, finally massing with glycerin of tragacanth (a better excipient than gum and water). The treatment of more soluble substances is exemplified in Atropine (which see).

Acidum Benzoicum

Five grains makes a fair mass with a drop of glycerin, but theriacanth gives the best results. For a white pill use glucanth.

Acidum Carbolicum

Phenol is one of the most troublesome things to make into pills that the dispenser meets with, owing to the fact that it tends to or actually does liquefy when rubbed in a mortar with other substances. With some extracts it forms a syrup; with alkaloidal salts, especially sulphates, it liquefies; and its behaviour towards many other organic substances is so precarious that dispensers will do well to reflect upon the table (Dr. E. A. Ruddiman's) printed on the opposite page, which shows that when any two of the substances named are mixed they form- P, a dry powder; L, liquid; DP, damp powder; PM, pasty mass. Alkaloidal salts behave similarly to antipyrin.

Phenol in detached crystals is the most convenient form for the dispensing-counter, especially for making pills. The excipients for it are about half a dozen- viz., wheaten flour, powdered soap and liquorice, soap and tragacanth with glycerin, powdered althaea and a trace of glycerin, kieselguhr and powdered curd soap, and hard paraffin with wheaten flour. Success with any of these greatly depends upon habit. The modern tendency is to use a dilute mass- 1 of acid in 4 or 5 -and to make it firm so that the pills will not dissolve quickly. For plain white pills the following are hard to beat:

The second of these masses is Mr. E. W. Lucas's 50-per-cent. The excipient to be used must depend greatly upon the nature of the mass. For example:

Fiat pil.

This makes a good pill by rubbing up the acid with half a grain of powdered curd soap, adding the subnitrate, and massing with a very little glycerin of tragacanth. A quarter of a grain of pepsin also makes a good mass.

Fiat pil. j.

Rub the phenol with an equal weight of soap; then add the powdered ingredients of the rhubarb pill, the podophyllin, and a little powdered tragacanth. Mass with a little treacle.

Divide in pilulas xij.

On mixing the camphor and phenol they liquefy. It is then difficult to combine the extract, therefore mix the three together, and triturate until uniform, add the powdered capsicum and 6 grains of powdered curd soap, mix and mass with kieselguhr. This is substantially the procedure with most of the liquefied phenol combinations, but soap is not always a desirable addition. Hard paraffin is the best substitute for soap, and next to it compound tragacanth powder.

Acidum Gallicum makes a good mass with a sixth to an eighth of its weight of glycerin.