White lead paint

The radioactive decay rates for °Pb and Ra in white lead paint taken from Emmaus in 1968 were 8.5 and 0.8 disintegrations per minute per gram of lead (dpm/g), respectively, (a) How many half lives of °Pb had elapsed between 1660 and 1968 (b) If Vermeer had painted Emmaus, what would have been the decay rate of °Pb in 1660 Comment on the reasonableness of this rate value. 

An excellent early comparative species analysis of chronic experimental lead poisoning is the 1922 paper of Sollmann on chronic intoxication induced by the white lead paint pigments basic white lead carbonate and lead sulfate. The data from this paper are presented below in the discussion dealing with experimental dose—toxic response relationships. 

White lead paint was used on exterior/interior surfaces in houses. 

If the normal carbonate is used, the basic carbonate or white lead, Pb(OH),. 2PbCO,. is precipitated. The basic carbonate was used extensively as a base in paints but is now less common, having been largely replaced by either titanium dioxide or zinc oxide. Paints made with white lead are not only poisonous but blacken in urban atmospheres due to the formation of lead sulphide and it is hardly surprising that their use is declining. 

Zinc oxide or zinc white is used in paints, but more preferable, because of its better covering power, is lithopone (a mixture of zinc sulphide and barium sulphate). Both paints have the advantage over white lead that they do not blacken in air (due to hydrogen sulphide). Zinc dust and also zinc chromate are constituents of... 

The metal is very effective as a sound absorber, is used as a radiation shield around X-ray equipment and nuclear reactors, and is used to absorb vibration. White lead, the basic carbonate, sublimed white lead, chrome yellow, and other lead compounds are used extensively in paints, although in recent years the use of lead in paints has been drastically curtailed to eliminate or reduce health hazards. 

Although white lead was the oldest white hiding pigment ia paints, it has been totally replaced by titanium dioxide, which has better covering power and is nontoxic (see Pigments). Nevertheless, basic lead carbonate has many other uses, including as a catalyst for the preparation of polyesters from... 

A frequently cited example of protection from atmospheric corrosion is the Eiffel Tower. The narrow and, for that age, thin sections required a good priming of red lead for protection against corrosion. The top coat was linseed oil with white lead, and later coatings of ochre, iron oxide, and micaceous iron oxide were added. Since its constmction the coating has been renewed several times [29]. Modern atmospheric corrosion protection uses quick-drying nitrocellulose, synthetic resins, and reaction resins (two-component mixes). The chemist Leo Baekeland discovered the synthetic material named after him, Bakelite, in 1907. Three years later the first synthetic resin (phenol formaldehyde) proved itself in a protective paint. A new materials era had dawned. 

An accurate observation of the first crater produced during the LIBS measurement with a camera revealed the presence of a blue substrate under the upper red layer of painting. The LIBS analysis demonstrated that the underlying blue substrate is composed by azurite (a copper based pigment) mixed with white lead (Figure 7). 

It s interesting to note that a Cinnabar+white lead layer over azurite+white lead substrate was used in the Maria Maddalena painting by Giacomo Cozzarelli (1453-1515), an artist contemporary to Beccafumi. 

Gallery (London). The sample contained white lead and ultramarine blue pigments Sample collected from a painting on copper leaf by F. Boucher, dated 1 750, containing 1.8 1.0 0.3 31.0 [9]... 

Bischof An obsolete process for making white lead (basic lead carbonate), invented by G. Bischof around 1900. Lead monoxide was reduced by the carbon monoxide in water-gas to form black lead suboxide, oxidized in damp air to lead hydroxide, slurried in dilute acetic acid, and carbonated with carbon dioxide. Piloted in Willsden, London, and commercialized by L. Mond in the Brimsdown White Lead Company. A sample of Bischof s white lead was used by Holman Hunt in his painting Light of the World, now in St. Paul s Cathedral, London. 

The zinc sulphate produced in this process can be turned more easily to commercial account than iron sulphate. If to the solution of the zinc sulphate resulting from the process sodium carbonate or sodium hydrogen carbonate is added, a precipitate of hydrated zinc basic carbonate or zinc carbonate is obtained, which on ignition in a furnace yidds zinc oxide (commercially known as zinc white ), water, and carbon dioxide. Zinc white has a commercial value as a basis or body In paints it has one great advantage over white lead, which is used for the same purpose, in that it is far less poisonous. This method of treatment of the residual... 

Lead carbonate (PbCO ) is found in nature as cerussite. It can also be produced in the laboratory by reacting sodium carbonate with chlorine. It is a crystalline poison that was, and to a lesser extent still is, used as a pigment in white house paints. 

The most important ingredient of a white paint used to be lead oxide. This was objectionable, as it could be swallowed by infants and lead to brain damage. Other white powders with strong covering properties were needed, and the current material of choice is titanium dioxide. Many painters still prefer lead oxide-based paint, as it has a more desirable warmer shade of white and it dries much faster than titanium oxide-based paint. When a mistaken stroke is made by a painter, lead paint that dries quickly can be covered up by another stroke, but titanium paint needs 3 days to dry before it can be covered up by another stroke. A solution is available in quick-drying additives to the titanium paint. 

Lead has numerous applications as metal, alloys and compounds. The major applications of the metal and its alloys such as solder are as materials of construction for pipe lines, plumbing fixtures, wires, ammunition, containers for corrosive acids and shield against short-wavelength radiation. Another major application is in storage batteries in which both the metal and its dioxide are used. Several lead compounds, such as lead chromate (chrome yellow), lead sulfate (white lead), lead tetroxide (red lead), and the basic carbonate are used in paints. 

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