CALOMEL, the sub-chloride, or °mild° chloride of mercury, HgC1 (or Hg,CI.), known to chemists as "mercurous chloride," to distin guish it from corrosive sublimate, HCl,,g which is known as "mercuric chloride." It is prepared by adding an alkaline chloride to a solution of a mercurious salt, usually the nitrate. The precipitate is thoroughly washed to remove the last remaining trace of the unchanged alkaline chloride. In the use of calomel as a medicine particular attention should be given to its lia bility to generate corrosive sublimate by de composition. This effect may be produced by bitter almonds or cherry-laurel water, or any other substance containing hydrocyanic acid, being administered simultaneously with it. Nitro-muriatic acid produces the same effects, as also, to some degree, the chlorides of potas sium, sodium and ammonium. If there is any possible chance of its adulteration with cor rosive sublimate, it may be tested by shaking a sample with a little alcohol and dipping a knife blade in the solution. The presence of
even so minute a proportion of corrosive sub limate as 1/500 of 1 per cent will be shown by a blackening of the steel blade. It is rendered ineffectual by the alkalies and alkaline earths. Calomel is regarded as the most valuable of the mercurial preparations, though some medical innovators reject it. It is employed as a purga dye, operating chiefly upon the liver by stimu lating its secretory functions. Being slow in its action, and liable to salivate if too long retained, it is usually administered with some saline cathartic. It is also given as a remedy for worms and as an alterative in derangement of the liver. Calomel occurs native in Spain, Bohemia, Serbia, Mexico and elsewhere, in the form of tetragonal crystals white in color (or nearly so) with a hardness of from 1 to 2 and a specific gravity of 6.48. In this form it is known to miners as horn-quicksilver.