POWDERING VEGETABLE DRUGS 57 



designated as dusted powders or meals, and are intended for internal 

 use or other special use. Nos. 80-100 are also largely intended for 

 internal use, but may also be employed for alcoholic percolation. 

 Nos. 50 and 60 are more generally better suited for percolation. For 

 aqueous extraction coarser powders are suitable, as Nos. 20-40. For 

 decoctions, broken drugs or even entire drugs, as leaves, leaflets and 

 some herbs, may be employed. 



In Europe the number of meshes are given in the metric system. 

 In Germany, for instance, 5 to 15 meshes to the centimeter indicate 

 coarse powders; 20 to 25 meshes, medium; and 30 to 50 meshes, fine 

 powders. Sieves for fine powders are usually made of silk thread, 

 horse hair for medium powder and wire for coarse powders. For very 

 fine meals bolting cloth is used in sifting. Powders containing 

 acid are not passed through metal sieves, as the wire would be corroded. 

 The fineness of the material used in sieve construction should harmonize 

 more or less with the fineness of the powder. The hygroscopic mois- 

 ture of the powder and that of the sieve threads interferes very ma- 

 terially with uniform sifting; hence the necessity of keeping powder and 

 sieve dry and cleaning the sieve repeatedly. Frequent cleaning is 

 especially required when sifting oily powders. 



8. Preservation of Powders. -As elsewhere stated, powdered drugs 

 deteriorate much more rapidly than do crude drugs; it is, therefore, 

 urged not to powder drugs until required for use, and never to powder 

 more than can be used within a comparatively short period of time. 

 Some powders deteriorate more rapidly than others, just as some 

 crude drugs deteriorate more rapidly than others. After grinding 

 the powder should again be carefully and thoroughly dried at a 

 moderate temperature and immediately placed in perfectly dry, well- 

 stoppered bottles or other suitable containers. Each package or bottle 

 of the vegetable powder should have upon it a statement of the age of 

 the drug from which the powder was made, date of powdering and 

 when it should be renewed and some effective method of compensating 

 for loss of active constituents should also be adopted as has already 

 been suggested. 



9. The Characteristics of Vegetable Powders. Since vegetable 

 powders are readily subject to deterioration and adulteration, it is 

 quite important that the pharmacist should be able to recognize the 

 characteristics of pure powders. While the odor and taste 'are the 

 same in quality as that of the crude drug, it should be kept in mind 

 that these properties are less marked quantitatively. The odor in 

 particular dissipates very rapidly. Attention should be given to 

 fineness, consistency and weight. If powders of oily drugs are dry 





