14- PHARMACY 



rated that no solid particles are in any way discernible. In other 

 words, the solid is liquefied, and its molecules intermingle with 

 those of the liquid (solvent). Solutions may be classified as simple, 

 chemical, unsaturated, saturated, and supersaturated. A simple 

 solution is one occurring as described above. Ho chemical change 

 is made. A chemical solution where chemical action takes place. 

 Unsaturated where the solvent contains less of the substance than 

 it will dissolve. Saturated when it contains all that it will dissolve, 

 and supersaturated when some means is employed to make the liquid 

 dissolve more of the substance than the usual amount of the solid. 

 Example, heat in most cases, or hydrochloric acid with corrosive 

 sublimate. 



The process of solution is applied to most organic drugs for the 

 purpose of separating the active ingredients from the insoluble inert. 

 The object is to dissolve the greatest amount of solid with the least 

 possible liquid (menstruum). It accomplishes two purposes. 1. 

 It gives a strong extract and (2) wastes no menstruum. Solution 

 may be accomplished in various ways. All are combinations of two 

 extremes, maceration and percolation, usually in the United States 

 of both. 



Maceration. This is simpler than percolation. It consists in 

 simply leaving the drug in contact with the menstruum under suit- 

 able conditions, for'a certain, or sufficient length of time. If macer- 

 ation alone is used, a definite amount of the drug is placed in a con- 

 tainer with a definite amount or portion of the menstruum and left 

 a certain time, in many cases two weeks. The liquid is then strained 

 off, the residue (marc) expressed and the mixed extract filtered. 



The process is influenced by (1) degree of comminution. The 

 finer the drug the less time is required. (2) The higher the tem- 

 perature the. quicker the solution. Different terms are given to 

 the process according to the degree of temperature employed. 

 Maceration is at room temperature. Digestion at 30°-40° C, Decoc- 

 tion, at boiling temperature. The application of heat is objection- 

 able in certain cases because it injures some of the desired constit- 

 uents or on account of the evaporation of either the constituent 

 or solvent. (3) Time. Usually the longer the better. (4) Men- 

 struum. This must in each case be adapted to the particular drug. 



Percolation. Percolation or displacement is the process 

 whereby a powder contained in a suitable vessel is deprived of its 

 soluble constituents by the descent of a solvent through it. (Rem- 

 ington. ) 



The solvent, which is poured on the top of the powder, in pass- 

 ing downward exercises its solvent power on the successive layers 

 of the powder until saturated, and is impelled downward by the 

 combined force of its own gravity and that of the column of liquid 

 above it, minus the capillary force with which the powder tends 



