CHAPTER II. 

 THE METHODS AND DEFINITIONS OF GALENICAL PHARMACY 



Drugs may be broadly classified as of (1) inorganic origin, (2) organic 

 origin. They may also be divided into two classes, (1) pure chemicals, 

 (2) galenicals. The pure chemicals are now prepared by neither pharma- 

 cist nor physician and in consequence the latter ordinarily needs to know 

 nothing more about the methods of their preparation than what he has 

 acquired as a student of chemistry. In regard to the methods of galenical 

 pharmacy he must be better informed, as a knowledge of some of the 

 methods and terms are essential in order that he may write prescriptions 

 intelligently. In consequence some of the terms and methods are defined 

 below. 



Fixed oils. (e.g. Castor Oil,*Olive Oil), fluid esters of the higher 

 fatty acids with glycerol (glycerin C3H 5 (OH) 3 ) obtained by expression from 

 fruits, seeds, etc. They cannot be distilled without decomposition. 

 They are freely soluble in ether, chloroform, carbon bi-sulphide, and ben- 

 zene, slightly soluble in alcohol, but insoluble in water. 



Fats, (e.g. Lard) are solid esters of higher fatty acids and glycerol 

 and are soluble in the same reagents as the oils. They are usually mixtures. 



Waxes, (e.g. cera flava) are usually mixtures of higher fatty acids 

 and glycerol and higher alcohols. 



Volatile or Essential Oils, (e.g. Oil of Cloves, Turpentine) are usually 

 mixtures of hydro-carbons chiefly fluids terpenes associated with more 

 highly oxidized members stearoptenes which may be obtained in a solid 

 state, (e.g. Camphor). They are usually isolated from plants by dis- 

 tillation. They are all soluble in ether, chloroform, carbon bi-sulphide, 

 and benzene, fairly soluble in alcohol, slightly in water. 



Resins, (e.g. Scammony Resin) solid preparations obtained from 

 oils by oxidation. The pharmacopoeial resins are usually mixtures of 

 resins as defined above and other bodies many of which are weakly acid. 

 They are insoluble in water but soluble in alkaline solutions, alcohol, and 

 ether. 



Oleo-resins, (e.g. Copaiba) natural mixtures of volatile oils and resins 

 semi-liquid in consistency. 



Balsams, (e.g. Benzoin, Balsam of Tolu) resins or oleo-resins either 

 liquid or solid which contain benzoic or cinnamic acids or both. 



Gums, (e.g. Acacia and Tragacanth) solid or semi-solid exudations of 

 plants which dissolve either partially or completely in water, forming a 

 mucilage or an adhesive jelly, and are precipitated by alcohol. They are 

 complex hydro-carbons yielding pentoses on hydrolysis. 



Gum-resins, (e.g. Myrrh) mixtures of gums and resins. 



*N.B. Students are strongly advised, when reading over this chapter, to look up 

 in Chap. V the examples cited. 



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