CHAPTER VI.

MECHANICAL SUBDIVISION OF DRUGS.

FIG. 82.

BEFORE employing vegetable drugs in the various pharmaceutical preparations, it often becomes necessary to reduce them to a state of comminution, or of powder, more or less coarse or fine as the nature of the drug and the desired preparation may demand. By simple contusion is generally understood a rather coarse division, brought about by crushing or bruising in suitable apparatus preparatory to finer reduction; for small operations an iron or brass mortar of bell or urn shape is employed, which should be deep and with a broad inner base, as shown in Fig. 82, the pestle being of such length and weight as will enable the operator to exercise considerable force if necessary. In contusing substances only such a quantity should be placed in the mortar at one time as to cover the bottom for the depth of an inch or two; and to avoid loss or unpleasant results from the escape of dust or particles of drug, a cover, provided with a hole through which the pestle passes, should be used. In place of the mortar and pestle a cutting knife can frequently be used with advantage. The Champion knife No. 2, Fig. 83, made by the Enterprise Manufacturing Co., of Philadelphia, is well adapted for the coarse division of roots, barks, and herbs, as it combines a drawing motion with pressure while cutting the material. When operating on large quantities, steam power is necessary, and the best apparatus for the purpose is that known as Mead's disintegrator (see Figs. 84, 85, and 86). The grinding is done in this mill by hardened steel beaters securely riveted on both sides of a steel disk. These beaters revolve on the feeding side of the mill between corrugated rings. The beaters catch the material as it enters the mill and beat it against the corrugates until it is sufficiently fine to pass between

Sectional view of mortar and pestle for contusion.

the disk and the face of the ring; as soon as it passes here it is on the discharge side of the mill, and all that is sufficiently fine is imme

diately driven out by the beaters on the back of the disk. What is not sufficiently fine. to discharge is caught by these back beaters. and beaten against the screens until fine enough to pass through. The screens are made of square steel, and present a grinding surface to the beaters and a discharging surface between each bar; they are 2 inches in width and extend around threefourths of the diameter of the mill, thus giving a large discharging surface without diminishing the grinding surface. The material as it is ground falls into the box or room below. The most effective work is achieved with the disintegrator running at high speed, 3000 revolutions per minute; under such conditions 600 pounds of wildcherry bark can be finely crushed in an hour.

The production of very fine powders of drugs has long since passed into the hands

Side view.

FIG. 86.

a

a, section of steel screen;

b, section of corrugated ring tached.

c, steel disk with beaters at

of the drug-miller, and even the coarser powders intended for percolation are to-day prepared by only a small number of pharmacists. For the latter purpose the drug mills shown in Figs. 87 and 88 will be found very desirable. In the New B Swift mill the grinding is done between plates placed horizontally, while in the Enterprise mill they are placed vertically. The grinding surfaces of both mills consist of circular chilled-iron castings studded with concentric rows of sharp teeth, those of one plate fitting between those of the other. The teeth decrease in size toward the centre, and the fineness of the powder is regulated by a pair of screws, by means of which the plates are made to approximate each other. One of the plates is stationary while the other revolves.

Separate sets of plates for coarse and for very fine grinding can be had for the mills. Care should be taken to clean the mill thoroughly after each operation, else the remaining dust will surely contaminate the drug next ground. The simplest method of cleaning is to run sawdust through the mill repeatedly; then loosen the screws and remove the grinding plates, so as to wash these with hot water, if necessary, and dry quickly. A great mistake often made by the inexperienced is the attempt to produce fine powders at once by screwing the plates close together, instead of grinding the drug coarsely at first and gradually tightening the mill; the first plan is apt to cause the material to become heated and cake, while the second plan will achieve the desired end more perfectly, with far less

plates, which possess the advantage over the usual styles of not allowing any material to pass through the mill unground (this some

times happens with vertical plates), and of not holding any of the ground material too long, whereby clogging may sometimes be caused with the horizontal plates. The mill is provided with an iron support, or may be had without it, to be mounted on a heavy block or box.

For grinding small quantities at the dispensing counter the No. 450 Enterprise mill (Fig. 90) is admirably adapted; it is constructed on the same principle as the larger Enterprise mill shown in Fig. 88. All the before-mentioned hand-mills can be opened horizontally, as shown in the illustrations, by means of a thumb-screw and hinge; thus the interior may be readily exposed to view for examination or cleaning. The material is supplied through a capacious hopper, with its base specially arranged for crushing the drug into coarse particles. The