64 PHARMACY 



in practice, but more narrowly it applies in pharmacy to insoluble mate- 

 rials suspended by suitable vehicles in water, the whole to be shaken 

 before using. They have no uniform strength. 



Emulsum, pi. emulsa. — Emulsions are similar to mixtures in that an 

 oily substance in a state of fine division is held in suspension in a gummy 

 or albuminous vehicle. They have no uniform strength. 



Syrupus, pi. syrupi. — Syrups are saccharine solutions. The vehicle 

 is usually water, although vinegar and alcohol may be used, and they are 

 all medicated except the simple syrup. They are not of uniform strength. 



II. — Preparations Whose Solvent Is Alcohol. 



Tinctura, pi. tincturae. — Tinctures are alcoholic solutions of non- 

 volatile principles, made usually by maceration and percolation of the 

 crude drug. They vary in strength; the more powerful drugs in 10 per 

 cent., the weaker drugs in 20 per cent, solution. The alcohol in tinctures 

 is often an important factor in the action of the preparation. Strong or 

 diluted alcohol is used according to the solubility of the active principle. 



Spiritus, pi. spiritus. — Spirits are alcoholic solutions of volatile sub- 

 stances, either gases or liquids or solids. They have no uniform strength. 



Elixir, pi. elixirs. — Elixirs are alcoholic solutions of drugs containing 

 sugar and aromatic substances. 



III. — Preparations Having Wine as a Solvent. 

 Vinum, pi. vina. — Wines are weak tinctures containing a small 

 amount of alcohol, the remainder of the solvent being white wine. They 

 are no longer official. 



IV. — Preparations Having as a Solvent Diluted Acetic Acid. 

 Acetum, pi. aceta. — Vinegars are solutions of the active principles of 

 drugs in acetic acid prepared by maceration and percolation. They are 

 not of uniform strength. 



V. — Preparations Made by Solution and Evaporation. 



Extractum, pi. extracta. — Extracts are concentrated preparations of 

 the crude drug. Ordinarily alcoholic solutions of the crude drug are 

 obtained by maceration and percolation, and then evaporated to a pasty 

 mass. They are usually stronger, weight for weight, than the crude 

 drug, but are not of uniform strength. 



Fluidextractum, pi. fluidextracta. — Fluidextracts are permanent, con- 

 centrated medicinal solutions of uniform strength. 1 mil of the fluid- 

 extract is equivalent to 1 Gm. of the crude drug. This result is obtained 

 by percolation (usually with alcohol) and partial evaporation.* 



VI. — Preparations Made by Distillation or Occurring Naturally, 

 as Exudations from Trees. 

 Oleo-resina, pi. oleo-resinae. — Oleo-resins are officially extracts ob- 

 tained by percolation of the crude drug with ether, and evaporation of 

 the solvent. They have no uniform strength. 



*The last (ninth) edition of the U. S. Pharmacopeia directs that many of the 

 fluidextracts be assayed so that they will contain a definite prescribed amount of 

 the active principle. 



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