322 MERCURY. 



which is prepared by decomposing a solution of muriate of ammo- 

 nia and corrosive sublimate by sub-carbonate of potass, consists 

 of the peroxide of mercury combined with the muriate of ammonia. 

 It is too acrid for internal use, but is frequently employed either 

 alone or mixed with powdered starch ? for the destruction of ver- 

 min ; made into an ointment with lard it forms a very useful 

 application in certain cases of porrigo, and some other cutaneous 

 eruptions. 



Sulpkurets of Mercury. 



There are two sulphurets of mercury ; the black sulphuret, 

 Hydrargyrum sulphur etum nigrum, commonly called JEthiops 

 Mineral ; and the bi- sulphuret, which is of a fine red colour, and 

 well known as a pigment under the names of Cinnabar and Vermi- 

 lion. The former is a very uncertain, inactive, and useless remedy, 

 and is scarcely ever employed in the present practice. Its dose, 

 as an alterative and anthelmintic, is from gr. x. to 3ss. or more. 

 The red sulphuret is only used in medicine for mercurial fumiga- 

 tion, a portion of it being thrown on a red-hot iron, while the 

 fumes are either inhaled or directed on the diseased parts. 



Chlorides of Mercury. 



Mercury combined with chlorine forms two very important pre- 

 parations. The one is termed the proto- chloride, and has been 

 long known by the name of Calomel, sub-muriate or mild muriate 

 of mercury. The other, the bi-chloride, is also well-known by the 

 name of Corrosive sublimate, and is the oxymuriate of mercury 

 of the London pharmacopoeia. 



Proto-chloride of Mercury, Sub-muriate of Mercury, 

 or Calomel. — Hydrargyri Submurias, Ph. L. — This compound 

 may be obtained by triturating four parts of the bi-chloride of mer ■ 

 cury {corrosive sublimate) with three parts of metallic mercury 

 until the globules disappear, then subjecting it to sublimation ; but 

 the proto-chloride may more easily be prepared by pouring into 

 the solution of the metal, in nitric acid, a solution of chloride of 



