Chemical elements
    Physical Properties
    Chemical Properties
      Lead Tetramethyl
      Lead Tetraethyl
      Lead Tetraphenyl
      Lead Ethoxide
      Lead Fluoride
      Lead Tetrafluoride
      Hydrofluoplumbic Acid
      Lead Chloride
      Lead Chloride Double Salts
      Basic Lead Chlorides
      Lead Tetrachloride
      Ammonium Plumbichloride
      Lead Chlorite
      Lead Chlorate
      Lead Perchlorate
      Lead Dibromide
      Double Salts of Lead Bromide
      Basic Lead Bromides
      Lead Bromate
      Lead Iodide
      Lead Iodide Complex Salts
      Basic Lead Iodides
      Lead Tetra-iodide
      Lead Iodate
      Lead Periodates
      Lead Suboxide
      Lead Monoxide
      Lead Hydroxides
      Lead Dioxide
      Plumbic Acids
      Hexahydroxyplumbic Acid
      Colloidal Plumbic Acid
      Potassium Plumbate
      Lead Plumbate
      Calcium Orthoplumbate
      Lead Orthoplumbate
      Red Lead
      Metaplumbic Acid
      Calcium Metaplumbate
      Lead Metaplumbate
      Basic Lead Plumbate
      Lead Sulphide
      Lead Sulphohalides
      Lead Polysulphide
      Lead Sulphite
      Lead Sulphates
      Lead Sulphate
      Basic Lead Sulphates
      Lead Hydrogen Sulphate
      Plumbic Sulphate
      Lead Persulphate
      Lead Thiosulphate
      Lead Dithionate
      Lead Selenide
      Lead Selenite
      Lead Selenate
      Lead Telluride
      Lead Tellurite
      Lead Azide
      Lead Azoimide
      Lead Hydrazoate
      Lead Imide
      Lead Hyponitrite
      Lead Nitrites
      Lead Nitrate
      Lead saltpetre
      Basic Lead Nitrates
      Lead Hypophosphite
      Lead Phosphite
      Lead Orthophosphate
      Lead Monohydrogen Phosphate
      Lead Dihydrogen Phosphate
      Lead Pyrophosphate
      Lead Metaphosphate
      Lead Arsenite
      Lead Orthoarsenate
      Lead Hydrogen Arsenate
      Lead Pyroarsenate
      Lead Antimonate
      Lead Carbonate
      White Lead
      Lead Formate
      Lead Acetate
      Sugar of Lead
      Complex Lead Acetates
      Plumbic Acetate
      Lead Tetra-acetate
      Lead Oxalate
      Lead Tartrate
      Lead Silicates
      Lead Borates
      Normal Lead Chromate
      Lead Dichromate
      Basic Lead Chromate
      Lead Molybdate
      Lead Tungstate
      Lead Metatungstate
      Lead Diuranate
      Lead Peruranate
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Lead Silicates

When litharge is fused with silica it forms a yellow, vitreous silicate which enters into the composition of the lead glazes used in pottery, and also of flint glass, which, on account of its high refractive power, is employed for optical purposes and for making artificial gems. The solubility of lead oxide in lead glass increases with temperature, and the yellow colour of glass rich in lead is attributed to the thermolytic dissociation of lead silicate, thus:

PbO.xSiO2PbO + xSiO2.

According to Mostowitsch, a number of lead silicates exist, in which the proportion of lead oxide to silica rises from PbO:SiO2 to 6PbO:SiO2.

By the study of the freezing-point curves of mixtures of lead oxide and silica, Hilpert and Weiller find evidence for the existence of only PbO.SiO2, and probably 2PbO.3SiO2. According to Hilpert and Nacken, however, 3PbO.2SiO2 exists, and probably 3PbO.SiO2.

Cooper, Shaw, and Loomis, from a study of heating curves, show the existence of Pb2SiO4, melting at 746° C., as well as PbSiO3, melting at 766° C.

Lead silicates are of importance in pottery manufacture, because; being less soluble than "raw lead" in dilute acid such as occurs in the gastric juice, they are less harmful to the workers. Thorpe and Simmonds have examined the solubilities of various lead silicates in dilute hydrochloric acid, and find that when the molecular proportion of acidic to basic oxide falls below 2:1 the silicate is readily attacked by the dilute acid; but when larger proportions of silica are combined with lead oxide there is little action. This is in harmony with the observation of Faraday that glass made of equal weights of silica and lead oxide does not become dull when exposed to the action of hydrogen sulphide; but that a glass made by fusing 8 parts of this glass with 1 part of potash is so tarnished. In the former case the ratio (acidic molecules)/(basic molecules) is 3.7, ih the latter about 2. It is well known, basic molecules not only that lead glass is easily fusible, but that it is easily reduced and blackened in the inner blowpipe flame. To account for this reducibility, Simmonds, who recognises the four simple silicates Pb2SiO4, PbSiO3, Pb2Si3O8, and PbSi2O5, as well as various double or complex silicates, introduces certain novel constitutional formula for these compounds, containing oxygen chains and linked silicon atoms.

In a further communication, Simmonds claims that the blackening of lead glass when heated in a reducing flame or a current of hydrogen is due not to the separation of metallic lead, but to the formation of a reduced silicate or "silicite" of lead. It was found, indeed, that powdered flint glass, reduced in hydrogen, contained no uncombined lead.

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