What is Red Lead oxide
Red Lead oxide commonly called Red Lead is an orange or red coloured powder. It is a water-insoluble compound that is prepared by the oxidation of metallic Lead or of litharge (Lead monoxide). It is a useful ingredient for the battery, glass & ceramic industry and it occupies an important place in the paint industry for its rust inhibiting character. Paint made with Red Lead is commonly used to protect iron and steel from rusting. Red Leads are utilised in a wide range of applications, such as battery manufacture, ceramics, anti-corrosive coatings, crystal glass and mining.
Properties of Red Lead oxide
- Other names: Lead Tetroxide; Lead(II,IV) oxide; Red Lead oxide; minium; triplumbic tetroxide; Orange lead; Paris lead; Pigment red 105; Plumboplumbic oxide; Lead tetraoxide;
- Formula: Pb3O4 / 2PbO.PbO2
- CAS No: 1314–41–6
- EC number: 215–235–6
- UN No: 1479
- Purity: 97% minimum
- Appearance: orange crystalline solid
- Molar Mass: 685.6 g/mol
- Density: 8.3 g/cm3
- Melting Point: 500oC
- Vapour pressure: 1.3 kPa (at 0C)
- Solubility: Insoluble in water 67.3mg/L
Red Lead is virtually insoluble in water and alcohol. However, it is soluble in hydrochloric acid present in stomach, therefore it is toxic when ingested. It dissolves in hydrochloric acid, glacial acetic acid, diluted mixture of nitric acid and hydrogen peroxide and hot alkaline solutions. It changes into black Lead sulphide while meeting hydrogen sulphide, while put outdoor in the open air it changes into while Lead sulphate
Uses of Red Lead oxide
Lead tetroxide is most often used as a pigment for primer paints for iron objects. Due to its toxicity, its use is being limited. In the past, it was used in combination with linseed oil as a thick, long-lasting anti-corrosive paint. The combination of minium and linen fibres was also used for plumbing, now replaced with PTFE tape. Currently it is mostly used for manufacture of glass, especially lead glass. It finds limited use in some amateur pyrotechnics as a relatively potent oxidizer. Red lead was also used for engineer’s scraping, before being supplanted by Engineer’s blue. It is also used for pottery glaze and Enamel. In the electric industry is used to make piezofiles. In the Chemical industry is used as a weak oxidizer.
Health & safety
R-phrases: R61 May cause harm to the unborn child. R20/22 Also harmful by inhalation and if swallowed. R 8 Contact with combustible material may cause fire. R33 Danger of cumulative effects. R50/53 Very toxic to aquatic organisms, may cause long-term adverse effects in the aquatic environment. R62 Possible risk of impaired fertility.
S-phrases: S53 Avoid exposure – obtain special instructions before use. S45 In case of accident or if you feel unwell, seek medical advice immediately (show the label where possible). S60 This material and its container must be disposed of as hazardous waste. S61 Avoid release to the environment. Refer to special instructions/ Safety data sheets.
For full details see MSDS for Red Lead oxide