220 INOEGANIC AGENTS 



day, or until vesication is produced, and the hair begins to 

 drop out, when its use is stopped for a time. Like other 

 mercury preparations, the red iodide must not be employed 

 in large quantities over an extensive surface. It is much 

 more irritant locally than blue ointment. 



UNGUENTUM HTDKAKGYEI NITKATIS. 



Citrine ointment is similar to unguentum hydrargyri 

 ammoniati (white precipitate ointment), but more power- 

 ful, and should be diluted with equal parts of lard. These 

 preparations are used for their stimulant action in granular 

 lids, chronic eczema, pityriasis, and for their anti-parasitio 

 effect in ringworm. 



SECTION VIL 



Arsenum. 



Arsenic is not used in the metallic state in medicine. 



Arseni Trioxidum (U. S. P.) 

 ACIDUM Arsenosum. Arsenous Acid. As^Oj. 



Synonym.-^Aci3.nm arseniosum, B. P.; acidum arsenic- 

 osum, P. G. ; arsenic trioxide, white arsenic, arsenicum 

 album, arsenic, arsenious anhydrid, E.; acid arsenieux, 

 arsenic blanc, fleurs d'arsenic, Er.; arsenicsaure, weisser 

 arsenic, G. 



Derivation. — Arsenical ores are roasted and purified by 

 sublimation. 



Properties. — A heavy solid, occurring either as an opaque, 

 white powder, or in irregular masses of two varieties; the one 

 amorphous, transparent and colorless, like glass ; the other 

 crystalline, opaque, or white, resembling porcelain. Both 

 are odorless and tasteless. The glassy variety dissolves 

 slowly in 30 parts of water ; the porcelain-like in 80 parts 

 of water. Arsenous acid is sparingly soluble in alcohol, but 

 soluble in glycerin, hydrochloric acid and solutions of the 



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