_Water_ will on some occasions be found a convenient expedient; powdered _Rhubarb_ or _Jalap_ may be thus made into masses without any increase of bulk, but the pills will be apt, if kept, to become mouldy. 3. In the formation of pills the ingredients should be hastily rubbed together, whenever they are liable to be injured by long exposure to the air; thus in the formation of _Pilulæ Hydrargyri submuriatis compositæ_, the compound is rendered less active by too long continued triture. See _Pulveres_. 4. In dividing pill-masses, it is usual to add to them, and envelope them in, magnesia; where calomel is present, I have satisfied myself by experiment that a _muriate of magnesia_ is formed under such circumstances, and it is owing to this partial decomposition, that the surface of the pill exhibits a greenish hue; starch, powder of liquorice,[299] or orrice root, might perhaps under such circumstances be more judiciously preferred. In Germany, the powder of _Lycopodium_ is generally used. Formerly, the pill was covered with gold leaf, which protected it from the influence of the stomach, and frequently rendered it unavailing. It has been observed that many of the pill-masses directed in our Pharmacopœias, are liable to become so hard[300] and dry by being kept, that they are unfit for that division for which they were originally intended; indeed Dr. Powel considers it doubtful whether the greater number of articles had not better be kept in powder, and their application to the formation of pills left to extemporaneous direction; the necessity of this is farther apparent, when we learn that it is a common practice for the dispenser to soften these masses by the application of a hot spatula, or pestle, which sometimes carbonizes, and frequently decomposes them. III. THEIR FORM OF PRESCRIPTION. In our extemporaneous directions, it is necessary to apportion with accuracy the quantity of active materials which we may wish each pill to contain, and since the proportion of the _constituent_ can rarely be exactly defined, the equable division of the whole mass, into a given number of pills, will be safer than defining the weight of each pill. A pill, the bulk of whose ingredient is vegetable matter, ought not to exceed five grains in weight, but where the substances which compose it are metallic and ponderous, it may without inconvenience weigh six or even eight grains. TROCHISCI. _Troches_, or _Lozenges_.