Exalgin

It was noticed that when the following were triturated in a mortar a valerianic-acid odour was developed:

Fiat pulvis. Mitte xij.

There is nothing in either of these substances to give rise to valerianic acid. It was concluded that the materials had been crystallised from an amylic solvent.

Hydronaphthol in crystals is exceedingly irritating to raw surfaces, and it is difficult to reduce it by mortar and pestle to a sufficiently fine powder.

Fiat pulvis aspersonus.

In this case the hydronaphthol was dissolved in a drachm of ether, and the solution poured upon the mixed powders contained in a warm mortar. The ether was quickly dissipated on stirring, and the powder proved satisfactory.

Hygroscopic Substances, such as acetate, carbonate, and citrate of potassium and iodide of sodium, ought not to be prescribed as powders, but if so each dose should be folded up in waxed paper, that again being covered with ordinary powder-paper. Do not attempt the reverse way. Granulated sodium citrate is now obtainable, and may safely be dispensed in powders wrapped in waxed paper. Calcium chloride is sometimes prescribed in powders. It should be powdered in a fairly hot mortar, and all the papers and the box dried in a warm place before use. Dispensed in this way the powders keep surprisingly well. Powder-boxes are a common source of damp owing to the paste used in their manufacture, and they should be well warmed before being used for powders with constituents possessing an affinity for moisture.

Iron Succinate

This deliquescent salt has been ordered in cachets. Use the smallest possible amount of mucilage to make the cachet edges adhere.

Liquids

It rarely happens that liquids are prescribed in powders, but it may be well to note that a grain of white kieselguhr will absorb at least 1 minim of a liquid without becoming wet, and still be fit to dispense in waxed paper. The following peculiar prescription looks very like a slip on the part of the doctor:

Misce bene. Divide in pulveres xxiv.

Powders were obtained with compound tragacanth powder and the plain gum which would scarcely mix with water. So the dispenser tried the mucilage, mixing it with the powders, drying and reducing to powder, then adding the bimeconate, and was surprised to find that this powder mixed nicely with water. This may have been intended by the prescriber ; if so, he was clever and has originated a wrinkle which is worth remembering.