Lead basic sulfates

Lead forms a normal and an acid sulfate and several basic sulfates. Basic and normal lead sulfates ate fundamental components in the operation of lead-sulfuric acid storage batteries. Basic lead sulfates also ate used as pigments and heat stabilizers (qv) in vinyl and certain other plastics. 

Leaded Zinc Oxide. Oxides containing more than 5 wt % basic lead sulfate are classified as leaded and are made ia the American process from high lead materials, usually lead sulfide mineral, or by blending ziac oxide and basic lead sulfate. There is only one manufacturer ia the United States and the product contains 20—28 wt % basic lead sulfate. Leaded oxides are used only ia mbber ia the United States. 

Paste mixing means the addition of sulfuric acid and water. The result is a fairly stiff paste with a density between 1.1 and 1.4gcm 3 containing 8-12wt% of lead sulfate. The water content of thus mix determines the porosity of the active material achievable later (cf. "curing" below). In the paste, a mixture of lead sulfate and basic lead sulfate is formed (cf. Table 1). In the usual mixing process between room temperature and 50 °C, tribasic lead sulfate is formed. The generation of the tetrabasic... 

When roasted in an air blast furnace, basic lead sulfate, Pb0 PbS04 (also known as sublimed white lead), is formed. 

PbO is more stable in alkaline solutions. Anodic oxidation of Pb leads to the selective growth of /I-PbO, which transforms into a-PbO in the course of prolonged polarization, as supported by X-ray diffraction studies and photoelectrochemical experiments [172]. In the presence of sulfate ions, simultaneous formation of basic lead sulfate with PbO has been observed, until the formation of 4Pb0-PbS04. At higher potentials, the oxide film in sulfate ions solution has a strong (110) orientation with microporous structure. X-ray diffractometry and photocurrent measurements have confirmed the presence of... 

Sulfates. Lead sulfate CAS 7446-l4-2. PbSOj. white precipitate, formed by reaction of soluble lead salt solution and sulfuric acid or sodium sulfate solution basic lead sulfate, "sublimed white lead." white solid, formed 11 > by reaction ol lead sulfate and lead hydroxide in waler Islow reaction , and t2i by roasting galenite in a ennem of air. 

Sublimed white lead Basic lead sulfate Pb20(S04) Paint pigment (white)... 

The variety of substances used as additives in polymers is considerable. For example, the fillers may include china clay, various forms of calcium carbonate, talc, silicas (diatomaceous silica), silicates, carbon black, etc. The impact modifiers typically include other polymers. Plasticizers include certain polymers with low (oligomers), dialkyl phthalates, dialkyl sebacates, chlorinated paraffin waxes, liquid paraffinic fractions, oil extracts, etc. Heat stabilizers include heavy metals salts such as basic lead carbonate, basic lead sulfate, dibasic lead phosphite (also acting as a light stabilizer), dibasic lead phthalate, stearates, ricinoleates, palmitates and octanoates of cadmium and barium, epoxide resins and oils, amines, diphenylurea, 2-phenylindole, aminocrotonates. The antioxidants include tris-nonyl phenyl phosphite, 2,6-di-ferf-butyl-p-cresol (BHT), octadecyl-3,5-di-terf-butyl-4-hydroxyhydrocinnamate, etc. The UV stabilizers include modified benzophenones and benzotriazoles. Processing lubricants include calcium stearate, stearic acid, lead stearate, various wax derivatives, glyceryl esters and long-chain acids. Fire retardants include antimony oxide, some pyrophosphates, etc. 

Generally, formation is carried out under constant-current conditions. The changes in temperature, electrolyte concentration, and cell voltage during plate soaking and formation are presented in Fig. 3.2 [2]. Chemical reactions commence between PbO, basic lead sulfates, and H2SO4 when the plates come into contact with the solution. 

Later in the formation process, the electrochemical reactions cause H2SO4 to be extracted from the plates and, consequently, the add concentration increases. At the end of the formation process, the add concentration is higher than that at the beginning of formation. This increase is due to the extraction from the plates of the acid used in the production of basic lead sulfates during paste preparation and in sulfation of the paste during plate soaking. 

The following chemical processes take place during soaking of the plates. These result in sulfation of the basic lead sulfates and of PbO, as follows. 

The above reactions start at the two surfaces of the plates and form two zones rich in PbS04, which grow towards the core of the plate (Fig. 3.3). Cured pastes are yellow in colour (basic lead sulfates and PbO are hydrated), while sulfated zones are grey. This difference in colouring allows easy determination of the growth rate of the sulfate zones towards the interior of the plate. The rate of movement of the reaction layer (FjuO into the bulk of the cured paste depends on the following parameters ... 

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