252 IRON SALTS 



Protargol, a silver albumose, containing eight per cent, of 

 silver, is a yellow powder, readily soluble in water and in 

 glycerin ; insoluble in alcohol. The solution is not affected 

 by heat, albumin, sodium chloride, caustic soda, or hydro- 

 chloric acid. It is said to be absolutely non-irritating. An 

 aqueous solution (1 to 10 per cent.) forms a penetrating 

 antiseptic of great value in the treatment of vaginal catarrh, 

 keratitis, conjunctivitis, and otorrhcea. Argonin, a com- 

 bination of silver casein and alkali, containing 4 per cent, of 

 silver, is a white powder, insoluble in cold water, but freely 

 soluble in hot water. Solutions of one to five parts in 100 of 

 water, are powerful germicides (Coblentz). 



IRON AND ITS MEDICINAL SALTS 

 IRON. Ferrum. Ferrum redactum. Fe. 



Iron is a lustrous grey metal, tenacious, malleable, ductile, 

 the least fusible of the useful metals, but readily welded at a 

 white heat. It is attracted by the magnet, and becomes 

 itself magnetic. It is widely diffused in rocks and soils, and 

 is present in the structures of plants and animals. Small 

 quantities occur uncombined, probably of meteoric origin. 

 Its chief ores are the oxides, comprising magnetic ore and 

 haematites ; the carbonates or clay ironstone, and black- 

 band ; and the bisulphide or pyrites. 



Iron forms three compounds with oxygen FeO, Fe 2 3 , 

 and Fe 3 4 the last being a compound of the other two. 

 Iron forms two series of salts the lower proto or ferrous 

 salts, in which it is divalent and magnetic ; and the 

 higher per or ferric salts, in which it is trivalent and non- 

 magnetic. 



The ferrous salts are reducing agents, are chiefly grey or 

 green, and in solution give, with hydrochloric acid and 

 sulphuretted hydrogen, negative results ; with ammonium 

 hydrosulphide, a black precipitate of hydrated sulphide 

 (FeS.H 2 0) ; with caustic alkalies, white or grey precipitates 

 of hydrated protoxide, Fe(HO) 2 , rapidly becoming green and 

 then brown ; with potassium ferrocyanide, a white precipi- 

 tate, gradually becoming blue by oxidation ; with potassium 



