INCOMPATIBILITY 45 



or Sodium; AgNOgj ZnSO^; Chloral; Cocaine Hydro- 

 chloride. 

 5 gms. (=25 grains in water q.s.gi). Alum; Carbolic 

 Acid; Borax; KCIO3; NaHCOs; HgCl^; Tartar Eme- 

 tic; Quinine Bisulphate; Citrated Caffeine; the ma- 

 jority of the soluble salts of Alkalies, Earths and Metals. 

 Smaller Quantities: Boric Acid, 4 ; Morphine Sulphate, 4.5 ; 

 Quinine Hydrochloride, 3; Quinine Sulphate, 0.13; Strych- 

 nine Sulphate, 2. 



IV. Solubility in Different Media. 



As a general rule, inorganic substances are more soluble in water 

 than in alcohol. Basic alkaloids are insoluble in water, more soluble 

 in alcohol. Alkaloidal Salts are soluble in either alcohol or water. 

 Gums are soluble in water, insoluble in alcohol. Resins and essen- 

 tial oils are the reverse. 



(In making mixtures, it must be remembered that spirits, tinc- 

 tures, and fluidextracts all contain alcohol.) 



Glycerin stands intermediate between alcohol and water as a 

 solvent. 



The following substances are: 



-■to 



1. Practically insoluble in water. Iodine, Calomel. 



2. Soluble in water, but almost insoluble in alcohol. Alum, 



IS^H^Cl, KCIO3, Tartar Emetic, ZnS04, Borax. 



3. Much more soluble in glycerin than in water. Boric 



Acid, Alum, Carbolic Acid, HgClg. 



INCOMPATIBILITY 



Incompatibility means lack of agreement. It may be defined 

 as that condition where two or more agents when brought together 

 result in chemical decomposition, physical disassoeiation, or thera- 

 peutic opposition. In some cases the change may be desirable 

 (white lotion, black wash), makes little if any difference, or may 

 be undesirable. The change may result in precipitating or destroy- 

 ing certain drugs of the mixture, changing color only, forming new 

 compounds without visible change or the ingredients may neutralize 

 each other. 



Incompatibility is usually classified as chemical, physical 

 (pharmaceutic) and physiological or therapeutic. 



Chemical Incompatibility occurs when a new chemical com- 

 pound results (chemical change). It may, in general, be recog- 

 nized in three ways: 1. Precipitation in which an insoluble pre- 

 cipitate is formed. 2. Effervescence or explosion- — evolution of 

 gas, — and 3. Change in color. In addition a new compoimd may be 



