56 POWDERED VEGETABLE DRUGS 



remain. It must also be kept in mind that the cells of different drugs 

 vary considerably in size. Drugs from aquatic plants, semi-aquatic 

 plants and plants growing in marshy soil, have larger cells than drugs 

 from plants growing in dry soil; hence the powders of the former drugs 

 need not be so finely reduced as those of the latter. 



While vegetable powders cannot be too fine, from a theoretical 

 standpoint, it is found that for practical purposes of extraction (perco- 

 lation) the very fine powders or meals are not suitable as they will not 

 allow the menstruum to pass through. The small particles pack to- 

 gether so closely as to check or prevent percolation. The fineness of 

 powders must not only be adapted to the methods and agents employed 

 in percolation, but also to the extractive it is desired to obtain. 



Powders intended for internal use cannot be too fine. As regards 

 the fineness of powders for the preparation of infusions, extracts and 

 tinctures, it may be stated that for alcoholic extraction the fineness 

 must be greater than for aqueous extraction, since alcohol does not 

 penetrate and permeate cell-walls so readily as does water. 



Some drugs cannot readily be reduced to a fine powder directly, as, 

 for instance seeds rich in oil; as nutmeg, croton beans, castor beans, 

 almonds, cardamom and other aromatic seeds. The oil is first re- 

 moved and the powdering done subsequently, or some inert substance 

 is added, as sand, sugar, starch, or dry woody substance, which serves 

 as a comminuting menstruum. Orange peel, lemon peel, slippery elm, 

 mezerion, etc., are first chopped into small bits, dried and then 

 powdered in the usual way. 



The use of Lloyd's reagent (prepared kaolin) for purposes of alka- 

 loidal extraction will have a very important bearing upon the future 

 therapeutic use of alkaloids. This new method will no doubt also 

 necessitate some suitable modification of powdering and otherwise 

 preparing the drug for extraction with this reagent. 



In the United States the size of the meshes of the sieves or the 

 fineness of the powders is indicated in the English system. 1 Very 

 fine powders, exceeding 100 meshes to the linear inch, are usually 



1 The U. S. P. specifies the size of the sieve mesh in terms of the linear inch but 

 does not indicate the particular gauge wire to be used. In the construction of 

 standard screen scale sieves, the U. S. Bureau of Standards specifies that the open- 

 ings shall increase in the ratio of \/2 or 1.414, the starting point being a screen 

 having an opening of 0.0029-inch which is the opening in a 200-mesh 0.0021 wire 

 sieve, thence increasing the opening by XI. 414 until the 1.050-inch 0.149 wire 

 sieve is reached. For purposes of closer grading or sizing of powders, the size of 

 openings increase in the ratio of \/2 or 1.189. Such close sizing is of course wholly 

 unnecessary for grading powdered vegetable drugs. The W. S. Tyler Company of 

 Cleveland, Ohio, manufacture standard screen scale testing sieves. 



