MERCURY 525 4. Mercuric Cyanide, Hg(CN)2.—This is nearly as poisonous as corro- sive sublimate, but has no corrosive action. It exists as white, prismatic crystals, having a bitter, metallic taste but no odour. It is soluble in 12 parts of water and in 15 parts of alcohol. Mercuric oxycyanide, HgO 3[Hg(CN)2], is a white, crystalline powder, soluble in 18 parts of water. Mercuric thiocyanate (sulphocyanide), Hg(CNS)2 is an insoluble powder which, when ignited, gives off obnoxious fumes of the metal and forms an exceedingly voluminous ash. It is moulded into pellets, which are known as " Pharaoh's serpents ", as these, when burnt, produce long snake-like tubes of ash. 5. Mercuric Nitrate, Hg(NO3)2.—This is crystalline, but deliquescent. It is used for painting on porcelain, and is used by hatters and furriers, as well as in veterinary medicine. It acts as a corrosive poison, and is similar in action to mercuric chloride. Symptoms of chronic poisoning occur among hatters and furriers. 6. Mercuric Sulphide (Cinnabar), HgS.—This is known in the verna- cular as hingul, ras sindoor, cheena smdoor or shingarf. It occurs as the chief ore of mercury, and is artificially prepared as a red, crystalline powder, which is then known as the pigment vermilion. It is regarded as non- poisonous, but its vapours are poisonous. Cases of acute poisoning have occurred from its use as a fumigant. Chronic poisoning has also occurred from it having been used to colour vulcanized rubber meant for artificial teeth. 7. Mercuric Sulphate, HgSCKt.—This is a white, crystalline powder, and acts as a corrosive poison. It has been administered in mistake for sulpho- carbolate of sodium, and has caused death. It has also been taken with suicidal intent. 8. Mercuric Methide (Mercury Dimethyl), Hg(CH3)2.—This is a highly poisonous liquid, and has produced death "by the inhalation of its noxious vapour. It has also produced insanity. 9. Mercurous Chloride (Subchloride of Mercury, Calomel), Hg2Cl2.— This is sold in the bazaar as raskapoor in fibrous, heavy, dirty white masses, often mixed with mercuric chloride. The pharmacopceial preparation, Hydrargyri subchloridum, is a heavy, amorphous, -white and tasteless powder, insoluble in water, alcohol (90 per cent), ether or cold dilute acids. The dose is 4 to 3 grains. When heated, it sublimes without fusing. It is converted into mercuric chloride by chlorine water, nitrohydrochloric acid, alkaline chlorides and common salt; hence it should never be prescribed with any of these substances. Exposure to sunlight decomposes it into mercury and mercuric chloride. It enters into the composition of the follow- ing preparations: — » 1. TabelloB Hydrargyri Subchloridi (Tablets of calomel or mercurous chloride).—Each, tablet should contain one grain. 2. Unguentum Tiydrargyri subchloridi (Calomel ointment).—It con- tains 20 per cent of calomel. Calomel is one of the ingredients of a non-official preparation, Pilula hydrargyri subchloridi (Plummer's pill), the dose being 4 to & grains. 10. Subsulphate of Mercury (Turpeth Mineral), HgSO4, 2HgO.—This is a lemon-yellow powder, sparingly soluble in water. It is used as an emetic in three to five-grain doses, especially on the continent and in the United States. It has occasionally caused death by acting as an irritant poison, 11. Mercurous Nitrate, Hg2(NO3)2.—This is colourless and crystalline. It is soluble in water acidulated with nitric acid, and is as poiscmoiis as mercuric nitrate.