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This method is usually preferred for the extraction of dried drugs, which have been reduced to the proper degree of fineness specified under each drug in part II.
After carfully weighing the drug, prepare the menstruum as prescribed under its heading in part II.
Carefully mix the ground drug with a sufficient quantity of this menstruum to render it uniformly moist. The moistening can be done with the help of a pestle or spatula in a suitable mortar. Then it is transferred into the percolater.
If the percolator is not provided with a stop-cock, insert a cork in the lower orifice,
having first made a small, longitudinal groove in such a way that, by pressing the cork into
the neck of the percolator with more or less force, the flow of the fluid may be regulated or
entirely stopped. Insert a plug of absorbent cotton into the neck above the stop-cock, cover
this with a layer of finely powdered glass half an inch deep, and lastly with a thin layer of
coarser glass. The grades of coarseness can be obtained by coarser and finer sieves. Fine white
sand may be used instead of glass. Spread the powdered drug first, sufficiently moistened with
a portion of the menstruum, little by little evenly upon the layers of glass, and press the
mass down with a broad flat cork on the end of a glass rod, more firmly if the mass is coarse
than if it is fine, and particularly if the menstruum be strongly alcoholic. Next cover the
surface of the mass with a disc of filter paper or a thin layer of finely powdered glass or
fine white sand. While holding down tha mass by means of the flat cork, pour the solvent upon
the contents of the jar until the mass is covered, allowing the fluid to run gently down the
glass rod so that the glass or sand may not be displaced. Then cover the percolator to exclude
dust and prevent evaporation. Close the valve or stop-cock as soon as the fluid begins to drop
and allow it to stand twenty-four hours or longer, according to the nature of the contents.
Next allow the fluid to pass through the percolator into the receiver, drop by drop, regulating
it by means of the stop-cock or cork so as not to allow the flow to exceed 10 to 30 drops in a
minute. The menstruum should be cautiously and frequently added so as to maintain a surface
above the powder, thereby preventing access of air. Proceed in this manner until the requisite
quantity has passed into the receiver. The strong tincture resulting from either the process of
maceration or percolation is then to be filtered through white filter paper, or absorbent
cotton, directly into glass bottles, the same to be marked with the sign Q 1/10, indicating
the strongest liquid preparation made directly from the medicinal substance, and also showing
the proportion of drug substance which the tincture represents, which proportion, under our
rules is common to very nearly all of our tincture. Changes of temperature will in some cases,
however, cause precipitation, which should be removed by filtration.
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