PHARMACEUTICAL PROCESSES 61 



after grinding, we use sieves of different degrees of fineness, designated 

 by numbers 20, 40, 60, 80, 100. These have reference to the number of 

 meshes contained to the square inch. Therefore, when a 60 powder is 

 directed to be used, it is that which will pass through a sieve containing 

 60 meshes to the square inch. 



Levigation. — Somewhat similar to trituration, but performed with a 

 slab and muller. These should be made of glass, or some non-absorbent 

 material. 



Elutriation. — This consists in mixing the powder, obtained by some 

 of the former comminuting processes, with water; agitating it; allowing 

 the coarser particles to settle, and pouring off the supernatant liquid 

 which holds the finer particles in suspension. The powder settles from 

 the latter and is dried. 



Mechanical Processes. 



Processes by which, liquids are separated from solids, and by which 

 active principles and soluble constituents are separated from the inert 

 portion of the drug. 



Decantation. — The process by which solids are allowed to subside in 

 a mixture and the supernatant liquid is slowly poured off or decanted. 

 Liquids which will not mix, or that are of different specific gravity, may 

 be decanted one from the other. 



Filtration. — This is the process of separating a solid insoluble sub- 

 stance from a liquid by passing the liquid containing it through a porous 

 substance called a flter. The filter commonly used consists of unsized or 

 bibulous paper, although cotton, muslin, felt, earthenware, and other sub- 

 stances are employed. ' 



Percolation consists in the following process : A pulverized vegetable 

 drug (containing both soluble and insoluble constituents) is placed in a 

 conical vessel, or percolator, and subjected to the action of a liquid called 

 a menstruum, when the soluble portion, or percolate, flows from the lower 

 opening. . The menstruum as it descends becomes more and more saturated 

 with the soluble constituents of the drug. The first that escapes is the 

 strongest, arid each successive portion of the percolate becomes weaker 

 until the drug is exhausted. The percolate should not drop faster than 

 10 drops per minute. Percolation is employed in making tinctures, fluid 

 and solid extracts, syrups and some other fluid pharmaceutical prepara- 

 tions. 



Clarification. — Is the process whereby cloudy substances are made 

 clear by the addition of some coagulable substances, as albumin or ichthy- 

 ocolla. It is the adding to any fluid, containing a sediment, a substance 

 which will carry down all undissolved particles, then filtering or decant- 

 ing the liquid. 



Chemical Processes Used in Pharmacy. 



Solution. — The process by which soluble substances assume the fluid 

 state through the action of a liquid. 



Lixiviation. — Employed to separate a soluble constituent from an in- 

 soluble porous body. The substance to be lixivated is mixed with water 



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