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 Sulphate, PbSO4

Lead Sulphate, PbSO4, is found naturally as the mineral anglesite or lead vitriol, which often occurs in large transparent crystals, isomorphous with those of celestine and heavy spar. The salt may be prepared artificially by precipitating a lead salt solution with sulphuric acid or a soluble sulphate. Thus obtained it is a white, microcrystalline powder. It may be obtained in a more distinctly crystalline form by causing it to be produced slowly; thus if the end of a platinum wire, covered with fused lead chloride, is allowed to dip into a layer of water which has been poured upon the surface of a saturated solution of potassium sulphate, crystals of lead sulphate are gradually formed. Lead sulphate is also formed by the interaction of lead dioxide and sulphur dioxide.

For commercial purposes lead sulphate is prepared as follows: Granulated lead is dissolved in acetic acid in steam-heated vats. The liquor is then poured off into a large wooden tank, and lead sulphate precipitated by the addition of sulphuric acid. After standing, the clear liquid, consisting of acetic acid, is pumped back into the vats to act upon a further supply of lead, whilst the precipitated lead sulphate is washed and dried.

Natural lead sulphate has a density of 6.30 to 6.39; the density of the synthetic salt is 6.17. The melting-point of the pure salt appears to be above 1100° C., but is difficult to determine on account of the loss of sulphur trioxide at this high temperature. There is, however, a transition point at 850° C. The molecular heat of formation of lead sulphate from its elements is 216,200 calories; the following are the heats of formation in other ways:

Pb + O2 + SO2 = PbSO4 + 145,100 calories.
PbO + H2SO4aq. = PbSO4(ppd.) + aq. + 23,400 calories.

Lead sulphate is not quite insoluble in water; at atmospheric temperature 1 part of the salt dissolves in about 22,000 parts of water. Dibbits found that 1 litre of water dissolves 0.038 gram PbSO4; but Sehnal found 0.0824 gram. The electric conductivities of aqueous solutions of lead sulphate at different temperatures (kt) have been measured by Kohlrausch, and the corresponding solubilities deduced therefrom.

Temperature ° C.0.373.4816.9818.0033.23
Millimols. per litre0.1100.1170.1340.1340.144

Applying the same principle, but reckoning the salt to be 82 per cent, ionised, Bottger has calculated the solubility of lead sulphate in water at 19.95° C. to be 4.21×10-2 gram per litre, a result which agrees closely with that of Kohlrausch. It has been pointed out, however, by Pleissner, that not only does the question of degree of ionisation enter into the calculation of solubility from conductivity data, but also that of hydrolysis. These authors have estimated the state of an aqueous solution of lead sulphate at 18° C. to be as follows:

[PbSO4] = 0.027 millimols. per litre
[SO4'] = 0.099 millimols. per litre
[Pb••] = 0.062 millimols. per litre
[Pb(OH)] = 0.037 millimols. per litre
[H] = 0.037 millimols. per litre
Solubility product: [Pb••]×[SO4'] = 61×10-10.

The solubility of lead sulphate is considerably less in dilute sulphuric acid than in water, but beyond a certain strength of acid the solubility again increases owing to the formation of complex ions. This is shown by the following figures:

Percentage H2SO40129648699
Grams PbS04 per litre0.0460.0270.0120.0460.1970.72

The solubilities of lead sulphite in hydrochloric acid of different concentrations at atmospheric temperature are as follow:

Grams HCl per 100 grams solution.10.616.322.027.531.6
Grams PbSO4 per 100 grams solvent0.140.350.952.112.86

and in nitric acid, also at atmospheric temperature:

Grams HNO3 per 100 grams solution.11.617.534.060.0
Grams PbS04 per 100 grams solvent0.330.590.781.01

Since ammonium acetate solution is used as a solvent for lead sulphate in qualitative analysis, the extent of its solvent action is of practical importance.

The following values have been obtained:

Temperature 25° C.
Grams NH4C2H3O2 per litre7.9815.9631.92
Grams PbSO4 per litre0.6361.383.02

Temperature 100° C.
Grams NH4C2H3O2 per litre.280320370450
Grams PbSO4 per litre71.298.8105.8111.0

It has been shown by Fox that with solutions of ammonium acetate up to a concentration of 3N the solid phase consists of lead sulphate, but with more concentrated solutions this phase consisted of crystals of (NH4)2Pb(SO4)2.

When lead sulphate dissolves in sodium acetate solution the solid phase consists of PbSO4, but when it dissolves in potassium acetate there is double decomposition with the formation of lead acetate and potassium sulphate, the latter uniting with the lead sulphate to form the complex sulphate K2Pb(SO4)2 as the solid phase.

Numerous other salts also increase the solubility of lead sulphate in water, prominent among which are ammonium nitrate, citrate, and tartrate.

Ethyl alcohol diminishes the solubility of lead sulphate, which is practically insoluble in pure alcohol; hence alcohol is added in order completely to separate lead as sulphate in qualitative and quantitative analysis.

Lead sulphate reacts with sodium hydrogen carbonate according to the equation:

PbSO4 + 2NaHCO3PbCO3 + Na2SO4 + CO2 + H2O;

whence it follows that carbon dioxide under pressure transforms lead carbonate suspended in sodium sulphate solution into lead sulphate.

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