63 PHARMACY 



and placed in a conical vessel^ the bottom of which is covered with straw 

 or coarse sand, and, after maceration has continued sufficiently, the satu- 

 rated portion, called the lye, is drawn off from an opening in the lower 

 part of the vessel. 



Crystallisation. — Is the concentration of a liquid containing a soluble 

 solid by means of heat, when on allowing it to stand until cool, crystals 

 form. Stirring during cooling will produce granulation. Solution, filtra- 

 tion and crystallization are the three best ways of obtaining pure salts. 

 Processes Requiring the Application of Heat. 



Liquefaction. — Is the melting of substances which at ordinary tem- 

 perature are hard, and when cool return to the same condition as before 

 heating, as resin, wax, lard, tallow. 



Evaporation.- — Is the .conversion of a liquid into steam or vapor. 

 Liquids which evaporate at ordinary temperature are called volatile, as 

 alcohol. To keep the heat below the boiling point of water, we use the 

 water bath, which cannot reach a higher temperature than 100° C. To 

 gradually increase the heat, use the sand bath. 



Distillation. — Is the vaporization of a liquid in a retort or a still, 

 by heat, and conduction of the vapor through a cooled tube, where it is 

 condensed and passes into a receiver and is called the distillate. Distilla- 

 tion is used to purify liquids or recover a volatile liquid from a solid, 

 solution or mixture. Where two liquids are mixed that have different 

 points of vaporization and are separated in this way, the process is called 

 rectification. 



Sublimation. -^HistiWaMon of a volatile solid. When the product is 

 in a solid form, it is called a sublimate, as iodine, camphor, etc.; when in 

 flakes, it is called flowers, as sulphur. 



Maceration. — ^A term used to denote the action of liquids upon drugs 

 at ordinary temperature. 



Digestion.- — Same process, with heat raised to 40° C. 



Menstruum,. — Any fluid substance used to dissolve a solid body or 

 extract its medicinal principles. 



Excipient. — ^Any substance used to give a pill mass proper con- 

 sistency. 



Exsiccate. — The process of removing all moisture, even the water of 

 crystallization, from a crystal, by the use of heat. 



Desiccate. — ^To remove all excess moisture. Heat not usually 

 employed in this process. 



Incineration. — The combustion of a substance for its ashes. 



Reduction is employed to recover a metal in its purity, when in a 

 combined state. 



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