This document discusses various lead pigments used to provide color to paints, including: 1. White lead pigment, whose chemical name is basic lead carbonate. It was traditionally used in white paints but is now replaced by titanium oxide due to its toxicity. 2. Red lead pigment, also known as sandhur, with the chemical formulae Pb3O4 or (2PbO.PbO2). It provides shades of red and orange paint. 3. Chrome yellow pigment, which is lead chromate (PbCrO4) that provides a yellow color when used in paints.

1. XII CHEMISTRY
CHAPTER 4
MS. SIDRA JAVED
Lead Pigments

2. Pigments are the substances
which are used to give the
proper colour to paints.

3. Lead Pigments 1. White lead Pigment
2. Red lead Pigment (Sandhur)
3. Chrome Yellow Pigment
4. Chrome Red Pigment
5. Turner's Yellow Pigment
6. Yellow Lead monoxide
(Massicot)
7. Red lead monoxide (Litharge or
Murda sang)

4. White lead Pigment
❖ Chemical Name: Basic Lead Carbonate
❖ Chemical formula: [2PbCO3.Pb(OH)2] or Pb3(OH)2(CO3)2
❖ Used in white paints as a pigment
White color darkens due to formation of PbS
❖ Toxic in nature
❖ It is now replaced by Titanium oxide due to toxicity

5. White Lead Pigment -
Preparation
Chamber process or Dutch process:
❖ Strips of lead are placed in Chambers
(earthenware)
❖ Mixture of acetic acid and steam is
passed for 2-3 days until lead is
corroded
2Pb+2CH3COOH+2H2O
→[Pb(OH)2Pb(CH3COO)2] + 2H2

6. ❖ A mixture of CO2 and acetic acid
vapors is passed through the
corroded lead for 3-4 weeks
❖ White lead is formed which is
then scratched, dried and
packed.
3[Pb(OH)2.Pb(CH3COO)2 +2H2O+2CO2
→ 2[2PbCO3.Pb(OH)2] + 6CH3COOH

7. ❖ A better white lead is
prepared by Passing CO2
into the suspension of
Lead oxide in water
containing little quantity
of Lead acetate
2PbO + 2CO2 + 2H2O + Pb(CH3COO)2
→ [2PbCO3.Pb(OH)2] + 2CH3COOH + O2

8. Red Lead Pigment (Sandhur)
❖ Chemical Formulae & Chemical name:
➢ Pb3O4 - Triplumbic Tetraoxide
➢ (2PbO.PbO2) - Lead sesqui oxide
❖ Color: Red
❖ Used to prepare paints of different shades from Orange
red to brick red
❖ Insoluble in water
❖ Soluble in acids

9. Red Lead pigment -
Preparation
❖ Prepared by heating PbO in
a revolving furnace with
excess of air about 4500C
6PbO + O2 2Pb3O4
4500C

10. Chrome Yellow Pigment
❖ Chemical Formula: PbCrO4
❖ Chemical Name: Lead Chromate
❖ Color: Yellow
❖ Occur in nature as Crocite
❖ Insoluble in water
❖ Soluble in nitric acid and cuastic alkalis

11. Chrome Yellow Pigment - Preparation
❖ Adding solution of Potassium Chromate K2CrO4 to
solution of Lead nitrate Pb(NO3)2
❖ Action of Potassium Chromate on Lead acetate
Pb(NO3)2 + K2CrO4 → PbCrO4 + 2KNO3
Pb(CH3COO)2 + K2CrO4 → PbCrO4 + 2CH3COOK

12. Chrome Red Pigment
❖ Chemical formula: PbCrO4.PbO or Pb2CrO3
❖ Chemical name: Basic Lead Chromate
❖ Color: Dark Red
❖ Used as red pigment

13. Chrome Red Pigment - Preparation
2PbCrO4 + 2NaOH → Na2CrO4 + Pb2CrO3 + H2O
❖ Prepared by digesting Lead
Chromate with NaOH

14. Turner’s yellow Pigment
❖ Chemical formula: PbCl2.4PbO
❖ Prepared by boiling NaCl solution with Litharge i.e.
Lead Monoxide
5PbO + H2O + 2NaCl → 2NaOH + PbCl2.4PbO

15. Yellow Lead monoxide
(Massicot)
Red Lead Monoxide
(Litharge)

16. End of Lesson