CALOMEL 293 



chloride. The calomel, rising in vapour, may be condensed 

 in fibrous cakes on the cool part of the vessel, or conducted 

 into a large chamber, where it falls in fine powder. Traces 

 of corrosive sublimate are removed by washing with boiling 

 distilled water. The powder is dried at a temperature not 

 exceeding 212 Fahr. 



Calomel is a dull- white, heavy, and nearly tasteless powder, 

 sometimes rendered yellowish by prolonged trituration. It 

 is inodorous, insoluble in water, alcohol, or ether. It is 

 slowly decomposed by light ; volatilises unchanged when 

 heated ; and yields mercurous oxide when acted on by 

 alkalies or lime water. 



ACTION AND USES. Calomel, being insoluble in water, has 

 no in-contact effect on the skin, but it is in part dissolved 

 by the gastric secretions. It irritates the gastric membrane 

 and glands, full doses producing emesis in man and carni- 

 vora. Similar irritation is exerted on the mucous membrane 

 of the small intestines, and it is consequently a cathartic. 

 It does not increase secretion of bile, but, acting as an 

 indirect cholagogue, it removes bile lodged in the duodenum. 

 Like other mercurials, repeated doses cause mercurialism, 

 and increase secretion of the salivary, pancreatic, and in- 

 testinal glands, and also of the kidneys. The earlier stages 

 of mercurialism are produced with the view of altering 

 metabolism and nutrition, and promoting especially absorp- 

 tion of fibrinous exudation. Externally, it is used as a 

 desiccant, stimulant, and anti-parasitic. 



GENERAL ACTIONS. Tuson showed that calomel and 

 distilled water, digested in a glass vessel at 100*2 Fahr. (the 

 temperature of the stomach), when mixed with either pepsin 

 or a 2 per cent, solution of hydrochloric acid remained un- 

 altered, even after twenty-four hours ; but when both pepsin 

 and hydrochloric acid were used, solution speedily occurred, 

 and a black precipitate of mercury sulphide was formed. 

 The mucus and fats of the canal, and also the bile, further aid 

 solution. It is chiefly absorbed as an albuminate, which, 

 although insoluble in water, dissolves in excess of albumin 

 and in sodium chloride solution. Small proportions even of 

 small doses of calomel are absorbed, and most of that ab- 

 sorbed, as well as that unabsorbed, is excreted by the bowels 



