LEAD 537 2. Lead Subacetate, Pb2O (CoH3Oo)2.—This is the chief constituent of Goulard's extract (Liquor plumbi subacetatis jortis), which is a colourless liquid with a sweet, astringent taste, and alkaline reaction. The extract contains about 42.5 per cent of lead subacetate. Goulard water or Goulard's lotion (Liquor plumbi subacetatis dilutus) is prepared by adding 12.5 parts of Goulard's extract to 1,000 parts of water. 3. Lead Carbonate, PbCO3.—This is a white, crystalline powder, almost insoluble in water, but soluble in dilute acids. In the form of a basic car- bonate or white lead (Safeda), (PbCO3) 2, PbH2O2, it is extensively used as a pigment in oil painting. It is also used as an ointment. Chronic cases of poisoning occur from the use of this salt. 4. Lead Nitrate, Pb(NO3)2.—This is a crystalline, poisonous salt, soluble in water, and is used in calico printing. 5. Lead Sulphate, PbSO4.—This is a heavy, white powder, insoluble in water and is, therefore, supposed to be non-poisonous, but cases of poisoning have occurred from sucking yarn coloured white with this salt. 6. Lead Chromate, PbCrO4,—This is a bright yellow, insoluble powder, known as chrome yellow, and is used as a pigment. Fatal cases of poisoning have occurred from the use of sweetmeats coloured with this salt. Joseph UttalST also reports three cases of chronic poisoning from the use of tobacco snuff adulterated with lead chromate as a colouring agent. 7. Lead Chloride, PbCl2.—This occurs as white, needleshaped crystals, sparingly soluble in cold water, but more so in boiling water. When heated in contact with air, it is converted into an oxychloride, which is employed as a white pigment, known as Pattinson's white lead. The yellow oxychlo- ride obtained by heating lead oxide and ammonium chloride is known as Cassel yellow, and is used as a pigment. 8. Lead Iodide, PbI2.—This is a tasteless, odourless and bright yellow powder, slightly soluble in cold water, but readily soluble in boiling water. It is used in preparing a non-official ointment, unguentum plumbi iodidi. 9. Lead Sulphide (Galena), PbS.—This is naturally found in the form of cubic crystals, but is sold in the bazaar in a powder form as Surma in place of sulphide of antimony which is used as a collyrium for the eyes. 10. Lead Monoxide (Litharge, Massicot), PbO.~This is called Mudra- sang in the vernacular. It is a pale brick-red or pale orange scaly mass, very slightly soluble in water, but readily soluble in nitric and acetic acids, It is used in preparing Goulard's extract and is also a constituent of a non- official preparation, emplastrum plumbi (diachylon plaster). Quacks use monoxide as a remedy for syphilis. It is also commonly used by painters and glaziers, and is a constituent of certain hair dyes. 11. Lead Tetroxide (Red lead, Minium), PbaO4.—This is a scarlet, crystalline powder, varying in colour, according to its mode of preparation. It is insoluble in water but partially soluble in nitric acid. It is called Sindur or Metia smdur in the vernacular, and is employed as a pigment. Lead Tetra-Ethyl, PbCCsHo)^—This is a clear, heavy, oily liquid, some- what volatile at the ordinary temperature. It has a specific gravity of 1.62, and has a peculiar sweetish odour. It is insoluble in ether and hot or cold water, but soluble in alcohol and acetone and miscible in all proportions with fats and oils. It decomposes in sunlight-with the formation of crystal- line lead triethyl hydroxide which, in the presence of a halogen, forms lead triethyl. 87. Jour. Amer. Med. Assoc., Jan. 28, 1928, p. 288.