Kroner lead yellow average
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- Country of manufactureBelarus
- Pre-packing- g
Lead krone represent isomorphic mixes of chromate with lead sulfate and on structure correspond to formula PbCrO4-n PbSO4l where n can be ranging from 0 to 2.
Besides, krone may contain the modifying additives [A1(OH)3, Ti (OH) 4, PAV, etc.].
Color of cranes — from yellow to light-lemon; with other things being equal color krone of subjects is more yellow, than contents Rbsgo4 is more.
Krone can crystallize in rhombic and monoklinny systems, and the last is stabler. At the same chemical composition the chromates and sulfolead chromates crystallizing in rhombic system are much lighter and more vysokodispersna, than the krone crystallizing in monoklinny system.
Specific surface — 16 — 30 sq.m/g, index of refraction — 2,7; particle size — from 0,2 to 2 — 3 microns, particle shape — granular or needle, rn aqueous extract — 5,0 — 7,0.
Gidrofobna krone, are water-insoluble also organic acids, are dissolved in hydrochloric and nitric acids.
At effect of alkalis redden (the main lead chromates are formed), at actions of H2S darken (PbS is formed) therefore it is impossible to mix krone with the pigments containing sulfur.
The thermal stability of cranes — to 90 °C, light resistance low.
In oil coatings krone change the main tone eventually: they turn green (Sg6+ — ► Sg3+) and darken owing to formation of peroxidates of lead.
Krone weatherproof and corrosion-resistant, possess high staining power.
Krone of monoklinny modification have higher light resistance and covering ability and rather lower dispersion and staining power, than krone of rhombic modification.
The most widespread methods of receiving lead chromes are: sedimentation from the index acetic and nitrate compounds of lead, continuous method of receiving cranes from metal Pb, and also from litharge and chromic anhydride.
Lead sulfate, though crystallizes in the same two systems, as lead chromate, but for it stable form is rhombic modification. Therefore at introduction of lead sulfate to structure the krone increases stability of rhombic modification of lead chromate in isomorphic mix.
Besides, for stabilization of rhombic modification of chromates and sulfolead chromates it is recommended to enter additives at synthesis of cranes: lead phthalate, aluminum hydroxide, hydroxide of titanium and some surface-active substances.