White lead
From Wikipedia, the free encyclopedia
| White lead | |
|---|---|
| Other names | basic lead carbonate |
| Identifiers | |
| CAS number | [1319-46-6] |
| Properties | |
| Molecular formula | Pb3 (CO3)2(OH)2 |
| Molar mass | 775.633 g/mol |
| Appearance | white powder |
| Hazards | |
| Main hazards | lead poisoning |
| Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa) Infobox disclaimer and references |
|
White lead is the chemical compound Pb3 (CO3)2(OH)2.[1] It was formerly used as an ingredient for lead paint and a cosmetic called Venetian Ceruse, because its opaque quality made it a good pigment. However, it tended to cause lead poisoning, and its use has been banned in most countries.
White lead has been the principal white of classical European oil painting. It is partly responsible for darkening of old paintings over time, because it reacts with trace amounts of hydrogen sulfide in the air, producing black lead sulfide. White lead has since been supplanted in artistic use by titanium white, which is somewhat less opaque and brilliant, but does not blacken and is not toxic.
Historically, white lead was produced by the Dutch process. This involved casting metallic lead as thin buckles. These were corroded with acid in the presence of carbon dioxide. Next they were placed in pots with a little vinegar (containing acetic acid). These were stacked up and left for six to fourteen weeks, by which time the blue-grey lead had corroded to white lead. The pots were then taken to a separating table where scraping and pounding removed the white lead from the buckles. The powder was then dried and packed for shipment.[2]
White lead occurs naturally as a mineral, in which context it is known as hydrocerussite[1]
[edit] References
- ^ a b Inorganic Chemistry,Egon Wiberg, Arnold Frederick Holleman Elsevier 2001 ISBN 0123526515
- ^ Lead411.org based on Warren, Christian. 'Toxic Purity: The progressive era origins of America’s lead paint poisoning epidemic'. Business History Review. Winter 1999, Vol. 73(4)
