Formula Pb(C2H3O2)2 Density 3.25 g/cm³ | Molar mass 325.29 g/mol Melting point 280 °C | |
Acetate.jpg/200px-Lead(II)Acetate.jpg) | ||
Appearance White powder or colourless, efflorescent crystals | ||
Lead(II) acetate (Pb(CH3COO)2), also known as lead acetate, lead diacetate, plumbous acetate, sugar of lead, lead sugar, salt of Saturn, and Goulard's powder, is a white crystalline chemical compound with a sweetish taste. It is made by treating lead(II) oxide with acetic acid. Like other lead compounds, it is toxic. Lead acetate is soluble in water and glycerin. With water it forms the trihydrate, Pb(CH3COO)2·3H2O, a colourless or white efflorescent monoclinic crystalline substance.
Contents
The substance is used as a reagent to make other lead compounds and as a fixative for some dyes. In low concentrations, it is the principal active ingredient in progressive types of hair colouring dyes. Lead(II) acetate is also used as a mordant in textile printing and dyeing, as a drier in paints and varnishes, and in preparing other lead compounds. It was historically used as a sweetener and for cosmetics.
Production
Lead acetate can be made by boiling elemental lead in acetic acid and hydrogen peroxide. This method of using acetic acid and hydrogen peroxide will also work with lead carbonate or lead oxide.
Pb(s) + H2O2 + 2 H+(aq) → Pb2+(aq) + 2 H2O(l)
Pb2+ + 2 CH3COO−(aq) → Pb(CH3COO)2
Lead acetate can also be made via a single displacement reaction between copper acetate and lead metal:
Cu(CH3COO)2 + Pb → Cu + Pb(CH3COO)2
Sweetener
Like other lead(II) salts, lead(II) acetate has a sweet taste, which has led to its use as a sugar substitute throughout history. The ancient Romans, who had few sweeteners besides honey, would boil must (grape juice) in lead pots to produce a reduced sugar syrup called defrutum, concentrated again into sapa. This syrup was used to sweeten wine and to sweeten and preserve fruit. It is possible that lead(II) acetate or other lead compounds leaching into the syrup might have caused lead poisoning in those who consumed it. Lead acetate is no longer used in the production of sweeteners in most of the world because of its recognized toxicity. Modern chemistry can easily detect it, which has all but stopped the illegal use that continued decades after legal use as a sweetener was banned.
Resultant deaths
Pope Clement II died in October 1047. A toxicological examination of his remains conducted in the mid-20th century confirmed centuries-old rumors that he had been poisoned with lead sugar. It is not clear if he was assassinated.
In 1787 painter Albert Christoph Dies swallowed, by accident, approximately 0.75 ounces (21 g) of lead acetate. His recovery from this poison was slow and incomplete. He lived with illnesses until his death in 1822.
Although the use of lead(II) acetate as a sweetener was already illegal at that time, composer Ludwig van Beethoven may have died of lead poisoning caused by wines adulterated with lead acetate (see also Beethoven's liver).
Mary Seacole applied lead(II) acetate, among other remedies, against an epidemic of cholera in Panama.
Cosmetics
Lead(II) acetate, as well as white lead, has been used in cosmetics throughout history.
It is still used in men's hair colouring products like Grecian Formula. The Food and Drug Administration considers this use safe because human testing showed lead did not enter the bloodstream and was not shown to be absorbed.
Lead acetate was banned in cosmetics by Health Canada in 2005 (effective at the end of 2006) based on tests showing possible carcinogenicity and reproductive toxicity. It is also banned in the European Union and has been on the California Proposition 65 warning list as a carcinogen since 1988.
Medical uses
Lead(II) acetate solution was a commonly used folk remedy for sore nipples. In modern medicine, for a time, it was used as an astringent, in the form of Goulard's Extract.
Lead(II) acetate has also been used to treat poison ivy.
Industrial uses
Lead(II) acetate paper is used to detect the poisonous gas hydrogen sulfide. The gas reacts with lead(II) acetate on the moistened test paper to form a grey precipitate of lead(II) sulfide.
An aqueous solution of lead(II) acetate is the byproduct of the 50/50 mixture of hydrogen peroxide and white vinegar used in the cleaning and maintenance of stainless steel firearm suppressors (silencers) and compensators. The solution is agitated by the bubbling action of the hydrogen peroxide, and the main reaction is the dissolution of lead deposits within the suppressor by the acetic acid, which forms lead acetate. Because of its high toxicity, this chemical solution must be appropriately disposed by a chemical processing facility or hazardous materials centre. Alternatively, the solution may be reacted with sulfuric acid to precipitate nearly insoluble lead(II) sulfate. The solid may then be removed by mechanical filtration and is safer to dispose of than aqueous lead acetate.
It was also used in making of slow matches during the Middle Ages. It was made by mixing natural form of lead(II) oxide called litharge and vinegar.
Sugar of lead was a recommended agent added to linseed oil during heating to produce "boiled" linseed oil, the lead and heat acting to cause the oil to cure faster than raw linseed oil.
Precautions
Lead(II) acetate, as with any other lead salts, causes lead poisoning.