for washing the plates; sometimes alcohol, or even acids, may be necessary to remove material tenaciously adhering to the moulds, but never should a sharp instrument be used in the perforations or on the pegs, as the smooth surfaces are likely to be scratched thereby. After the plates have been carefully cleansed and rinsed with cold water they should be dried with a soft towel, the water remaining between the pegs being readily shaken out; when dry, the perforated plate should be placed in proper position on the peg-plate, and the whole laid aside on a level, solid surface, away from heat. When a suitable paste has been made the perforated plate is placed upon a level surface, preferably a thick glass plate, and, by means of a horn spatula of the shape shown in Fig. 255, the mass is forced into the holes so as to fill these completely, any excess of material being removed with the spatula; the plate is then reversed and, if necessary, more of the mass is forced into the holes until they are completely filled and both sides present a smooth, solid surface. The operation is best explained as follows: The operator grasps the spatula in such a manner that the forefinger rests on the

FIG. 255.

Horn spatula.

flat surface near the acute angle of the diagonal edge, with the middle finger resting near the obtuse angle of the same edge; the thumb rests against the long side, and the third and little fingers against and slightly around the short side of the spatula. The mass having been placed on the mould under the spatula, the latter is drawn with pressure over the mould diagonally toward the operator. After the required number of holes have been filled, the upper plate is carefully brought down over the lower one with the marks or numbers at the end of the two corresponding, and by the aid of the guide-pins the pegs are pressed into the corresponding holes and the tablets thus forced out, remaining on the ends of the pegs; after a few moments they may be removed, either by inclining and tapping the plate or by carefully brushing them into a suitable receptacle, preferably a bolting-cloth sieve. The tablets should then be dried either by exposure to the ordinary room-temperature, protecting them from dust, in closets supplied with circulating warm air, or in small quantities on a perforated tray near a stove or register, as the nature of the medicinal ingredients may permit. By means of hard-rubber moulds holding 100 tablets each, experienced operators average from 6000 to 8000 tablet triturates per hour, unless the material be especially difficult to manipulate.

Some manufacturers use an apparatus somewhat differently con-structed, as shown in Fig. 256. The two plates are held in frames. hinged together and so arranged that the peg-plate can be brought down accurately over the perforated plate carrying the tablets, and by pressing the pegs down through the perforations the tablets are made to drop out upon a sheet of paper placed underneath for their reception. The weight of different kinds of tablet triturates made with moulds of the standard size mentioned above will vary considerably according to the density of the mass being manipulated. Thus tablets containing grain of morphine sulphate each, will weigh about 1.2 grains; tablets containing grain of calomel will

weigh about 1.4 grains; and tablets containing 1 grain of calomel will weigh from 1.9 to 2 grains each; while the size of all these tablets will be the same. The weight of the tablets will also be considerably influenced by the pressure upon the spatula exerted by each individual operator during the process of moulding, which varies with nearly every person, and hence in large manufacturing establishments operators are kept at work on certain lines of tablet triturates with which they have become familiar so as to insure uniformity in weight. The weight of a certain tablet having been ascertained, a memorandum should be made of the details regarding combination, diluent, and excipient, for future reference.

Every formula for new tablet triturates must be determined tentatively in order to ascertain the exact amount of sugar of milk or other diluent required. The simplest plan is to weigh off enough of the active ingredients to make a given number of tablets (say 25

or 50); mix this with a quantity of diluent known to be insufficient, moisten with the necessary excipient, and press the mass into the holes of the plate intended to be used. Then moisten more of the same diluent with the excipient, and with this paste fill the holes remaining unfilled from the first operation; smooth off both sides of the tablets, place on the ejecting-pegs and force the tablets out. For larger operations the tablets should then be thoroughly dried and weighed, the weight of the dry tablets less the weight of active ingredients used representing the weight of the diluent required to make the given number of tablets. In small operations, particularly those of the dispensing-counter, the drying may be omitted, and, instead, an extra number of tablets (4 or 5) made out of the plain diluent, added to the number first obtained, before the whole is thoroughly mixed in a mortar; this extra material is necessary because the first tablets, when worked up again in the mortar, generally form a more compact mass, and hence would prove insufficient for refilling the required number of perforations. The porous nature of most tablet triturates and the very fine state of division of the ingredients render it essential that the tablets be carefully kept in dry, tightly stoppered amber-colored vials, which protect them perfectly against the air, moisture, and the effects of the light. They should be stored in a cool and dry place. Small amber-colored homeopathic vials are likewise the best receptacles for dispensing these tablets. Tablet triturates containing substances readily affected by air or light are often made into compressed lenticularshaped disks and subsequently coated with sugar or chocolate.

Hypodermic tablets are simply tablet triturates intended for the convenient preparation of solutions for subcutaneous injection. Since they contain definite quantities of the active agents, they are admirably adapted for physicians' use at the bedside, and are very extensively employed. As a rule, pure sugar of milk or pure cane-sugar is used as the vehicle, although sodium sulphate has also been employed by some manufacturers. They are made in the hardrubber moulds already described, the perforations being usually inch in diameter and or inch in depth. This produces a tablet that can readily be dropped into the barrel of a hypodermic syringe, in which it is quickly dissolved upon addition of 10 or 15 minims of water and subsequent agitation.

Tablet saturates differ from tablet triturates only in the manner of introducing the medicinal agents. They are made by first preparing plain sugar-of-milk tablets, in the moulds already described, and having placed the tablets, when dry, on a glass plate, the desired quantity of tincture, fluid extract, or solution, is dropped upon each tablet individually from a pipette. A glass cover is then placed over the tablets and the fluid allowed to saturate them uniformly, after which they are dried in a current of warm air.

CHAPTER XXXI.

POWDERS.

In addition to what has already been said about pulverization, in the chapter of Mechanical Subdivision of Drugs, there remains yet to be considered the administration of medicines in powder form, which, presenting certain advantages, is still largely employed by physicians. The powder form is a most convenient method of giving medicines in the case of very young children and persons who are unable to swallow pills, as well as where the fluid form is unavailable for any reason. It is true, many substances are not suited for administration in powder form, particularly bulky vegetable powders, deliquescent salts, and such as contain large quantities of water of crystallization, as sodium phosphate or sulphate, etc.; but while the fluid form of medicine is probably to be preferred in the majority of cases, the bitter or nauseous taste of some substances becomes more marked in solution than in the dry state. Among the substances best adapted for dispensing in powder form are insoluble chemicals, such as calomel, bismuth salts, sulphurated antimony, some salts of the alkaloids, and vegetable drugs given in small doses, such as ipecac, opium, and catechu. Physicians frequently direct their patients to dissolve or mix the powder in water, and in such cases the powder form is preferred on account of convenience or for reasons of economy.

FIG. 257.

Powders, as a rule, are composed of two or more substances; to insure an intimate and uniform mixture they must be triturated in a mortar, preferably made of porcelain, of the shape shown in Fig. 257, this style presenting a sufficient broad surface at the base, whilst its curved sides prevent the ejection of material during trituration. It is assumed that in the majority of cases the individual ingredients are already in the state of very fine powder, and therefore only require thorough mixing, which is best accomplished by trituration with light pressure only, so as to avoid caking and sticking to the sides of the mortar; the contents of the vessel should also occasionally be scraped from the pestle and sides of the mortar if necessary, as this aids more perfect admixture. Whenever substances which are themselves in

a coarsely powdered or granular condition are ordered in a powdered mixture, they must be reduced to a very fine powder by themselves, no attempt being made to reduce them in the mixture.

A few general rules will serve for guidance in the preparation of mixed powders. Whenever sugar is one of the ingredients it should be of the kind known as bolted or lozenge sugar. When small quantities of potent or other substances are to be dispensed in powders, they should first be well triturated with a portion of the diluent, and finally incorporated with the remainder of the more bulky powders; or, if no diluent has been ordered, they should be triturated with a small quantity of sugar of milk, to insure their more uniform distribution in the mixture. The proper plan is to place about 5 grains of sugar of milk in the mortar, add the active ingredient, and then triturate thoroughly, as, by this means, more accurate subdivision is effected, and none of the active material is likely to adhere to the sides of the mortar. Soft extracts and essential oils must be treated in the same manner.

Whenever physicians prescribe quantities which cannot be weighed conveniently, such as, 10, 4, or of a grain, and metric weights less than 10 milligrammes, the plan of preparing a dilution of the substance with sugar of milk, by trituration, in such proportions that a weighable amount of the mixture shall represent the desired quantity of active ingredient, as indicated on page 343, should invariably be followed, as by this method accuracy of division is best obtained.

Certain substances of a crystalline structure-notably also those of a resinous character-have a tendency to become electrical by friction, particularly if pressure be employed; such bodies are said to be idioelectric, and must be triturated lightly, or, if pressure is necessary to reduce them to fine powder, they must be sprinkled with a little alcohol, whereby the trouble is obviated, or the powder, which adheres firmly to the mortar and pestle, and is prone to fly off in all directions if scraped with a spatula, must be set aside for a while until the electric condition has disappeared. To this class belong common pine resin, and the resins of guaiacum, jalap, and scammony, also quinine alkaloid, acetanilid, salol, phenacetin, and others. The removal of these in fine powder form from the mortar is attended with more or less difficulty unless previously slightly dampened.

When substances which differ materially in specific gravity are to be mixed in powder form-as, for instance, bismuth subnitrate with magnesia, sodium bicarbonate with charcoal, or zinc oxide with lycopodium-the best plan is to place the heavy substance in the mortar and incorporate the lighter body gradually by adding small portions at a time. Calcined magnesia and charcoal are also more readily mixed if the charcoal be gradually added to the magnesia with very light trituration; only in this manner can a powder of uniform appearance be obtained. Whenever large quantities of these pow