Chloride of lead 2824900010
Lead chloride PbC12 forms white rhombic crystals with a silky sheen. Specific gravity 5.9, melting point 498 ° C, boiling point 954 ° C. Lead chloride is moderately difficult to dissolve in water. Therefore, it is precipitated from not too dilute solutions of lead (II) salts when ions are added to them Сl-. Lead chloride is much more difficult to dissolve in alcohol than in water. It dissolves more easily in glycerin than in water (2.04 g per 100 g).
Technical production of lead chloride is carried out either by dissolving lead oxide or basic lead carbonate (lead white) in hydrochloric acid, either dissolving the granular lead in dilute nitric acid and subsequent precipitation with hydrochloric acid; the nitric acid released in the second part of the process can be reused to dissolve lead.
PbO + 2HCl = PbСl2 + Н2O;
Рb3 (OH) 2 (СО3) 2 + 6HCl = 3РbСl2 + 2СO2 + 4Н2O
3Рb + 8НNO3 = 3Рb (NO3) 2 + 2NO + 4Н2O
Pb (NO3) 2 + 2HCl = PbCl2 + 2NH3
In a stream of carbon dioxide, lead chloride can be distilled without decomposition. When heated in air, it undergoes hydrolytic decomposition under the influence of air moisture. It is reduced to metal by heating in a stream of hydrogen or with coal in the presence of water vapor.
Molten lead chloride solidifies, forming a horny mass (horny lead) ... In the molten state, lead chloride has significant electrical conductivity; likewise, it conducts well in aqueous solution at ambient temperature. Based on the data of the conductivity of a saturated solution at 25 ° C, it follows that the content of undissociated salt in it is 6%; the rest of the lead chloride is approximately half dissociated primarily (according to the equation РbС12 = РbСl + + Сl-) and half secondarily (according to the equation РbСl2 = Рb2 + + 2Сl-). The solution is acidic to litmus; however, the degree of hydrolytic degradation is insignificant (according to Lei's data, it is about 0.6% at 100 ° C in 0.01 N solution).
Lead chloride forms a rhombic lattice in which each Pb atom is surrounded by nine C1 atoms; two chlorine atoms are closest to Pb (distance 2.67 Å), the third C1 atom - at a distance of 2.88 Å; the other six chlorine atoms are located at a distance of about 3.05-3.29 Å.
PbC12 can attach redundant ions Сl -, forming complexes. As a result, the solubility of lead chloride increases with the addition of large amounts of chlorides or HC1 (small amounts of ions C1- decrease the solubility). The lead (II) halides known in the solid state correspond mainly to two types: M2PbCl4 and MPbCl3; Along with them, there are also salts of other types, for example MPb2Cl5.
Lead chloride easily forms basic chlorides. The latter can be considered as compounds of PbC12 with PbO and with Pb (OH) 2. Some of them are found in nature in a crystalline state, for example, 2PbO ∙ PbC12. Under the action of lime water on a hot concentrated solution of lead chloride, the compound Pb (OH) 2 ∙ PbCl2 is obtained, which is marketed in the form of paint (Pattinson's lead white). Lead chloride also forms double compounds with pyridine and thiourea.