1. Liquor potassæ added to its solution gives a yellow precipitate. This precipitate, if washed, dried, and heated in a test tube, gives a ring of metallic mercury in the form of globules in the cool part of the tube. In like fashion corrosive sublimate itself may be reduced and volatilized if heated with black flux.
2. On adding a solution of iodide of potassium to a small quantity of the solution, a bright scarlet precipitate, soluble in excess of iodide of potassium, is produced.
3. If a drop or two of a solution of corrosive sublimate, slightly acidulated with hydrochloric acid, be placed on a sovereign, and the solution and the gold be touched with a piece of zinc or an iron key, the mercury will be deposited as a bright silvery stain on the gold.
Calomel (Subchloride or Chloride of Mercury) is a heavy white powder, which is usually regarded as a safe medicine. Yet, in some peculiar constitutions, it has caused excessive salivation and death, even though only a few grains have been given. In large doses it may be regarded as an irritant poison. It is distinguished from corrosive sublimate by forming a black precipitate with caustic potash and by its insolubility in water.
Ammonio Chloride of Mercury (White Precipitate).—This substance is a chalky looking powder, containing about eighty per cent. of mercury. It produces vomiting, purging, great pain in the stomach, cramps, and convulsions. Out of fourteen cases, collected by Dr. Taylor, in which from a few to forty grains were taken, only two proved fatal.
The remaining preparations of mercury, which in rare instances have been used as poisons, are the Red Oxide of Mercury (red precipitate); the Red Sulphuret of Mercury (cinnabar or vermilion); the Cyanide of Mercury; the Nitrates of Mercury; and Turpeth Mineral.
Mercury may be separated from organic admixture by Reinsch’s method.