SOLUBILITIES OF SALTS 43 



HATJSTTJS — DRENCH 



A haustus or drench may be defined as an extemporary liquid 

 preparation intended to be given immediately in one dose. 



EIECTTJARIUM — EIECTTJARY 



Electuaries are medicinal pastes to be smeared on the teeth 

 of animals where they melt at body temperature and are absorbed 

 or are free to act locally upon the tissues of the mouth and throat. 

 Usually a specified quantity is dispensed as a sample dose or one 

 of the common domestic measures may be used. 



ASSAYING 



On account of the different conditions under which plants grow, 

 the different methods used in collecting, drying and preserving 

 them and the effects of age upon their active ingredients, crude 

 drugs vary greatly in strength. Because of this variability the use 

 of the active principles has certain advantages ; they are more rapidly 

 absorbed, have a constant strength and many may be used subcu- 

 taneously. On the other hand, there are some cases in which it is 

 impossible or too expensive to isolate the active principles in pure 

 form, or there may be a preference for the mixtures or combina- 

 tions in the same proportions in which they occur in nature, so that 

 the pharmaceutic preparations and even the powdered crude drugs 

 are very often employed, even when the active ingredients are 

 available. 



In order to make some of the more potent drugs uniform in 

 strength, the United States Pharmacopoeia standardizes them to con- 

 tain a definite percentage of the active principles by assaying. The 

 process of assaying is a process by which the strength of a prepara- 

 tion is determined. 



There are three kinds of assay processes for drug standardiza- 

 tion: chemic (volumetric), pharmaceutic (galvimetric) and physio- 

 logic. The physiologic process is devised for certain drugs whose 

 active ingredients are not readily isolated. 



SOLUBILITIES OF SALTS 



A general idea of solubility of salts is essential for prescribing 

 or dispensing them. The following tables according to SoUmann 

 include only those salts in general use : 



I. Arranged by Acids. 

 Group A. Salts mostly soluble. 



1. Acetates and Nitrates: all soluble except bismuth subni- 

 trate. 



