302 MERCUROUS IODIDE 



action. An ointment, made of one part precipitate to nine 

 of white paraffin ointment, is used as a parasiticide, and as 

 a mild mercurial in skin diseases. 



Mereuro-zinc cyanide, a combination of mercuric cyanide 

 and zinc cyanide, has been much used in human surgery. 

 It is a white powder, recommended by Lord Lister as a non- 

 irritating and very powerful antiseptic. 



MERCTJROUS IODIDE. Green Iodide. Hydrargyri lodidum 



Viride Hg 2 I 2 . (Not official.) 

 MERCURIC IODIDE. Red Iodide. Hydrargyri lodidum 



Rubrum. Biniodide of mercury. HgI 2 . (B.P.) 



Mercurous iodide is an unstable salt, prepared by tritu- 

 rating together iodine and an excess of mercury with a little 

 alcohol, or by mixing solutions of mercurous nitrate and 

 potassium iodide. Although not so active as the higher 

 iodide, twenty grains destroyed a rabbit within twenty-four 

 hours, and a drachm a pointer dog in five days (Cogswell). 



Mercuric or red iodide, formed by the interaction of 

 mercuric chloride and potassium iodide, is a vermilion- 

 coloured, heavy, crystalline powder, with a disagreeable 

 metallic taste. It 'is almost insoluble in water, sparingly 

 soluble in cold alcohol, but soluble in ether, acids, solution 

 of potassium iodide, and most saline fluids. 



ACTIONS AND USES. Mercuric iodide is as irritant as 

 mercuric chloride or nitrate. But the presence of iodine 

 increases the solubility of albuminates, and, compared 

 with the chloride, the iodide is more quickly absorbed and 

 excreted. Twenty grains given to a rabbit induced gastro- 

 enteritis, collapse, and death in twenty-four hours. It is 

 used internally, combined with potassium iodide, to arrest 

 the growths of actinomycosis and scirrhous cord, and solu- 

 tions are applied externally as antiseptics, and ointments 

 as stimulants, counter-irritants, and caustics. 



The biniodide, dissolved in water, by the aid of potassium 

 iodide, in ether, and alcohol is frequently used for the same 

 antiseptic and stimulant purposes and in the same strength 

 as the perchloride. The B.P. ointment, of 20 grains iodide 

 to 480 grains of benzoated lard, is not sufficiently strong for 



