CHAPTEK III 

 PHARMACEUTIC METHODS 



There are several processes in the manufacture of pharmaceutic 

 preparations, and these vary v^ith the nature of the crude drug and 

 the character of the desired product. These processes are : 



Desiccation or Drying. This is usually the first step in the 

 preparation of crude drugs. It has three advantages: it reduces 

 bulk, assists preservation, and facilitates comminution. Drying was 

 formerly done by storing in a dry, airy loft, but now most of it is 

 done in special ovens. The degree of heat must not be high enough 

 to destroy any of the desired or unstable ingredients. The next 

 step is that of comminution. 



Comminution. This is the reduction of the drug to smaller 

 fragments. This process is now mainly done by machinery, quite 

 similar to that used in grist or flouring mills. On a small scale the 

 drug mill, which is similar in action to the coffee mill, may be used. 

 The grinding has to be repeated several times in case of some drugs 

 to get the powder fine enough. The mortar and pestle are used for 

 friable substances. These are made of glass, wedgewood, porcelain 

 and iron. 



Trituration. Trituration is employed where a finer powder 

 is desired than can be obtained with a mill. It consists of rubbing 

 with a rotary motion, not pounding, the substance in a mortar with 

 a pestle. Some substances will not powder alone but will if mixed 

 with another substance (pulverization by intervention), — sugar of 

 milk. Sometimes the substance requires moistening, as camphor 

 with alcohol. 



Certain drugs percolate better if used in a certain degree of 

 fineness. They are, therefore, sifted and classified accordingly. If 

 a very fine powder is desired of an insoluble substance, it may be 

 mixed into a thick paste with water or alcohol and rubbed between 

 two polished slabs (Levigation) or placed on a marble slab, moist- 

 ened with alcohol or water and rubbed with a muUer. In rubbing, 

 a circular or figure eight motion should be used. 



Separation. This is usually the next step in the preparation 

 of drugs. Its purpose is to separate the desired ingredients from 

 the inert or undesired. It may be accomplished in three ways. If 

 the desired ingredients are volatile, they may be driven off by heat, 

 i.e., by distillation or sublimation. If the substances are not 

 volatile, the separation is usually done by exposing the crude drugs 



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