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softened, then to dry the mass upon a steam-bath, and finally to crush it in a mortar, or to grind it in a mill to a No. 20 granulation.

When a caked mass is to be reduced, by rubbing in a mortar, to a No. 20 granule, the material should be transferred to the sieve at short intervals, in order to separate that portion which has been reduced to the proper fineness; otherwise, by continued rubbing, the greater portion of the material would be reduced to a fine powder.

Extracts may also be incorporated in the form of a dry, impalpable powder, if the proportion be small, and in such cases it is also a good plan to add some powdered starch to the material and extract; next, sufficient water is added, and well incorporated, the mixture passed through a No. 12 sieve, then dried, and, lastly, forced through a No. 20 sieve. It is not necessary to use any adhesive material, such as acacia or cane sugar, for tablets containing extracts, unless the proportion of extract be very small. Spongy bodies like charcoal must be in impalpable powder, and not less than 25 per cent. of cane sugar should be added for granulation. If the charcoal cannot be obtained in a finely subdivided state, it is a good plan to add the proportion of sugar as above, to wet the mixture to such a state that it forms small cakes, and to dry perfectly. The cakes are then reduced to very fine powder, moistened with sufficient water to make the mass pass through a No. 12 sieve, the granulation dried, and then reduced to granules, passing through a No. 60 to 80 sieve.

The powdered pepsin of the market is of a spongy nature, like charcoal, and is best prepared for compressing by adding one-tenth of its weight of cane sugar, then spraying diluted alcohol over the mixture, mixing thoroughly until all particles have been moistened, but are still in about No. 80 powder, then drying and compressing.

Spongy substances should be fed to the machine in a very finely granular form. The large size granules offer too much resistance to the punches, and the tablet crumbles very easily. Spongy bodies, as a rule, require no lubricant.

Scale pepsin and most of the other scale preparations can be compressed by reducing them to No. 30 or 40 granules, and lubricating them.

Salts containing water of crystallization, organic or inorganic, which cannot be compressed without being first granulated, as, for example, lead acetate, zinc sulphate, alum and quinine sulphate, are best treated in the following manner:

The salt is reduced to a fine powder, mixed with one-twentieth of its weight of powdered gum arabic, moistened sufficiently with water to pass it through a No. 12 sieve, dried, again reduced to fine powder, mixed with one-tenth of its weight of cane sugar, moistened with just enough water to make it pass through a No. 12 sieve, then dried, first without, and lastly by aid of heat. The

mixture is then forced through a No. 20 sieve, lubricated and compressed.

Bodies which are hygroscopic or deliquescent are best granulated with gum arabic exclusively, taking one-tenth of the weight of the substance and water for moistening.

Combinations of rhubarb and soda are best granulated by adding to them one-tenth of their weight of cane sugar, and granulating with a mixture of one volume of glucose, 1 volume of water and three volumes of alcohol, well mixed, this mixture preventing the action of the alkali upon the rhubarb.

Glucose is an excellent medium for making tablets hard and tough, so that they will not readily disintegrate, as, for example, lozenges which are intended for slow solution in the mouth. To improve the lozenge, the greater portion of the material should be cane sugar, with 10 per cent. of gum arabic, and the glucose should be diluted with 25 per cent. of water before being added.

In tablets to form effervescing solutions or to form new compounds when added to water, the constituents should be granulated separately, and mixed in a perfectly dry granular condition just before being compressed.

A very important quality which compressed tablets should possess is that of rapid disintegration and solution. This is brought about by adding finely powdered starch, to the amount of from one-twentieth to one-tenth of the weight of material, to the granulated substance ready to be compressed. It is most important for certain insoluble bodies, such as phenacetin, acetanilid, sulphonal, etc., that they disintegrate rapidly. These are best granulated with one-tenth of their weight of cane sugar, water being used for moistening. As stated before, the addition of acacia retards rapid disintegration and solution; hence it should not be used where cane sugar acts as a sufficiently adhesive agent.

Fig. 362 illustrates the simplest form of a compressed tablet machine; this consists of a cast steel cylinder, into the base of which fits a short post with a concave surface. A steel plunger, having a corresponding concave depression on its lower extremity, is used for compression. The granule is introduced into the cylinder, and after inserting the plunger, a quick, sharp blow is struck by means of a wooden mallet, whereby the powder is compressed; then, after the cylinder is removed from the base, the plunger is tapped, which forces the tablet out into a proper receptacle. An improvement on this is the tablet machine illustrated in Fig. 363. Its construction is simple, being operated by means of a lever. It is capable of turning out tablets quite rapidly. For the preparation of large quantities of tablets, the larger machines of the market afford all that is desirable.

The pressure used for compressing the tablets should be just as light as possible, for the firmer the pressure the slower the disintegration of insoluble bodies, firm pressure not affecting very

soluble substances, since their solution takes place from the surface. The pressure should be regulated so that the tablets may readily be broken in half by the fingers, but should not break to pieces when dropped upon the floor. With a light pressure the material has a greater tendency to stick to the face of the punches.

The dies and punches should be of very hard temper and should be kept in good condition. They should be polished from time to time by the aid of finely powdered emery, preferably on a lathe. If this is not at hand, a round smoothened end of a piece of wood answers very well, and is used by dipping the end in oil, then in the emery, and rubbing over the surface of the punches. For polishing the dies, a rounded piece of wood, a little

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smaller than the bore of the die, dipped in the oil and emery, is well adapted.

If the surface of the dies and punches is not kept smooth and polished, the material works into the uneven surface and adheres to it, making a tablet with rough surface and scraped edges, necessitating the frequent cleaning of the faces of the punches.

If the dies be of soft temper, such bodies as exert considerable friction, as acetanilid, phenacetin, and antipyrin, will wear down the die quickly in that portion where the tablet is compressed, and by the constant wear the die is widened at this spot, especially at the point of the upper and lower surface of the tablet where there is the most wear, hence the tablet is slightly wider than the bore of the remaining portion of die. In being forced upwards

to be expelled from the die, the tablet is forced into a narrower space than that into which it had been compressed, which tends to bend it and loosen the flat or convex upper or lower surface, which may readily be split off by the thumb nail, but which will fall off spontaneously after the tablet has been shaken about some little time. This is termed "capping."

The best remedy for the "capping" is a hard-tempered die; but this is not always at hand. Dampening the granulation very slightly with water will prevent it; but this increases the adhesive qualities, and the material is more liable to stick to the punches. However, if these are smooth and well polished, little trouble will be experienced from the sticking qualities.

Reducing the pressure is another remedy; but, if the punches are not in good condition, the material will stick to them.

Changing the weight of the tablet is still another remedy, the tablet to be compressed in a portion of the die that is not worn.

EXTRACTA-(Extracts).

EXTRACTS are solid or semi-solid preparations obtained by the evaporation of solutions of the medicinal principles of drugs. According to the solvent employed in exhausting the drug they are designated as alcoholic, hydroalcoholic, aqueous, ethereal, acetic, or ammoniated extracts.

The strength of these preparations bears no definite relationship to the drug, for the amount of solid extract* obtained depends on the nature of the drug, the solvent employed, and the mode of preparation. The more aqueous the menstrua, the greater is the yield of extract, the more alcoholic the menstrua, the smaller the yield.

It must be remembered that the activity of most drugs resides, as a rule, in certain definite principles, which generally constitute the smallest portion of the bulk of an extract; the other constituents of the drug, embracing gums, starch, inert extractive, coloring matters, etc., constitute the larger inert portion soluble in water. Hence, the solvent selected for extraction must be such as to take up all the active, with as little of the inert matter as possible. If an unscrupulous manufacturer were to employ water or a feebly alcoholic menstruum for extracting a drug whose active principles are soluble in alcohol only, he would obtain a large yield of inert extractive matter, while his neighbor who employs alcohol only, would obtain a very small yield of a very active preparation. If both products were sold in the market at equal rates, the former would be a fraud upon the public. Extracts also vary in consistence. Some are as liquid as honey, others have the consistence of a pill mass, and still others are hard and dry, hence there is not likely to be any uniformity of strength, with such variations as these. Therefore, unless there is some guarantee of intrinsic value based on its alkaloidal strength or physiological activity, no reliance can be placed on the strength of one extract as compared with another.

Solid extracts are prepared either—

(a) From the dried and powdered drug, by extraction with a solvent,

or

(b) From the fresh, moist drug, by expression alone.

* Prepared with official menstrua (U. S. Pharmacopoeia, 1880), the yield in extract is, according to J. Lammer, Jr., “Proceed. Amer. Phar. Association," 1887, p. 35:

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