Lead forms several nearly stoichiometric oxides with narrow phase limits, namely PbO, Pb3O4 and PbO2, as well as several compounds with oxygen having relatively larger phase limits.
In commercial production by thermal method molten lead is directly oxidized by a mixture of air and water vapour. In the cupellation process in which a hearth is used or in kettles in the Barton Process both modifications Red Tetragonal PbO and Yellow Rhombic PbO form in varying proportions depending on temperature and cooling rate.
The storage battery industry uses Lead Oxide i.e a Powdered Lead Oxide with metallic Lead usually in the ratio 70:30.This Oxide is manufactured by a thermal process (Barton Oxide) or by attrition milling process (Mill Oxide)
The Red Lead Pb3O4 is generally prepared by batch oxidation of Massicot by air at about 450-500 deg c. Red Lead is beneficial in improving the electrochemical performance of cell and batteries. It is being used extensively in positive tubular plate for Inverter, Stand by and Traction Batteries.
The Red Lead is in a higher oxidation state than litharge (ratio of Pb:O=1.33) and its electrical conductivity is also greater. Batteries made with Red Lead in positive paste (not exceeding 14% of the total paste weight) is formed quicker with higher initial capacity than those from Lead Oxide. In tubular positive plate Red Lead is extensively used for Inverter, Solar & Traction Batteries.
Red Lead is produced in calcining furnaces in which the raw material is agitated while being heated at the optimum temperature for oxidation to the required product. For production of Red Lead a range of 450-500 deg c. is used. The Furnace is discharged when the desired amount of Pb3O4 is reached. Oxide with 80% Pb3O4 is made with 16-18 hours of calcining.
General Technical specification
| PARAMETER | UNIT | SPECIFICATION |
PbO2 |
% | 30 ± 2 |
PB304 |
% | 80-90 |
Sb – Antimony |
% | 0.0010 Max |
Bi – Bismuth |
% | 0.020 Max |
Cu – Copper |
% | 0.0030 Max |
Fe – Iron |
% | 0.0020 Max |
Mn – Manganese |
% | 0.0005 Max |
Retention on 100 BSS |
% | Nil |
Retention on 300 BSS |
% | 5 Max |
Apparent Density |
g/cc | 1.30 to 1.60 |
For many years the plates of lead acid battery have been produced from Lead Oxide, a mixture of finely divided lead and tetragonal PbO in the proportion of 30% lead and 70% PbO. Although this material is generally satisfactory, it suffers from the disadvantages that it is variable in composition and requires lengthy processing after pasting to oxidize free lead. Plates made from Lead Oxide also require cycling before they achieve full capacity.
Lead Oxide manufactured by the ball mill process is almost pure tetragonal while that produced by the Barton Process contain up to 10% of the orthorhombic form, depending on the temperature during the process.
General Technical Specifications
| PARAMETERS | UNIT | SPECIFICATION |
| Color | Blackish to Greenish Grey | |
| Apparent Density | (Gm/cc) | 1.33 - 1.6 |
| Retention on 240 mesh (63 micron) | % | 0.1 |
| Retention on 325 mesh | % | </=5 |
| Water Absorption | mg/100gm | 110-120 |
| Acid Absorption | mg/gm | 180-220 |
| Free Lead | % | 28-32 |
| Lead Monoxide | % | 68-72 |
Litharge/Yellow Oxide chemically known as Calcined orthorhombic PbO and is yellowish in color. The most important difference from Lead Oxide is it is free from presence of free lead. The absence of free lead significantly improves the reproducibility of paste mixing and curing process. Barton pot is used as the primary step to produce Messicoat. To produce Messicoat, Refined Lead ingots of minimum 99.98% purity level is used. This Messicoat is then transferred into the Litharge furnace to generate the yellow oxide powder. The desired quality such as , apparent density, particle size etc is properly examined by experts.
Litharge is extensively used by manufactures of Stabilizers. It is also been used in paint industries, Lead glass industries. Litharge is also an important ingredient used by industries such as rubber industries, lubricant industries, PVC industries etc.
General Techenical Specifications
| PARAMETER | UNIT | SPECIFICATION |
| Colour | Yellow | |
| Retention on 240 mesh BS Sieve/63 micron IS Sieve |
% | 0.10 |
| Apparent Density (scott) | gm/cc | 1.8 to 2.2 |
| Subsidence in Petrol / Water | mi/gm | 0.40 to 0.42 |
| Acid Absorption | mg/gm | 80 to 110 |
| Solubility in Water | gm/litre | 0.10 |
| Oil Absorption | % | 0.1 |
| Insoluble matter in Acetic Acid | % | 0.08 |
