Lead brown

Bronsted theory See Bronsted-Lowry theory. bron-steth, the-3-re brown lead oxide See lead dioxide. braun led ak.sTd ... 

Synonyms lead(lV) oxide lead peroxide lead superoxide brown lead oxide plattnerite... 

Elemental composition Pb 46.73%, C 21.67%, H 2.73%, O 28.87%. The compound may be identified from its physical properties and elemental analyses. Additionally, a measured quantity of the compound may be hydrolyzed with water and the product, the brown lead dioxide formed may be determined by x-ray method or analyzed for lead by instrumental techniques (See Lead.)... 

In 1801, the year in which Hatchett discovered niobium, Andres Manuel del Rio, a professor of mineralogy in Mexico, examined a specimen of brown lead ore from Zimapan and concluded that it contained a metal similar to chromium and uranium. Little has been written concerning the personal life of del Rio. He was born in Madrid on November... 

It was there that he discovered a new metal which, because of the red color that its salts acquire when heated, he named erythronium (44). Upon further study, however, he decided that he was mistaken, and that the brown lead ore from Zimapan was a basic lead chromate containing 80.72 per cent of lead oxide and 14.80 per cent of chromic acid (12). His paper therefore bore the modest title, Discovery of chromium in the brown lead of Zimapan (21). In 1805 Collet-Descotils confirmed del Rio s analysis (22), and for twenty-five years no more was heard of the new element, erythronium. 

In his textbook of mineralogy published in Philadelphia in 1832, however, del Rio said that the metal in the brown lead is not chromium but vanadium, the very same (el mismo mismisimo) which I called pancromo and eritrono on page 61 of my translation [of Karsten s Tables, Mexico, 1804] (72). 

After N. G. Sefstrom had discovered vanadium in a soft cast iron from Eckersholm, Sweden, no mineral containing it as an essential constituent was known until Wohler analyzed the specimen of brown lead from Zimap n which del Rio had sent to Europe by Baron Alexander von Humboldt (73). Wohlers researches (45) proved that he had been... 

The most outstanding achievement of del Rio s long, useful life was his discovery in 1801 of the metal now known as vanadium. He found that the brown lead mineral, Plomo pardo de Zimapan (8), from the... 

When von Humboldt visited Mexico in 1803, del Rio gave him several specimens of the brown lead ore. Von Humboldt sent some of them to the Institut de France with an explanatory letter giving del Rio s analysis and his conclusions regarding the close resemblance of the new metal to chromium and uranium. A more detailed description addressed to Chaptal was lost in a shipwreck (10). 

Since the properties of erythronium closely resembled those which Fourcroy had ascribed to the recently discovered metal chromium, del Rio lost confidence in the importance of his discovery and concluded that his supposed new element was, after all, nothing but chromium (11). In a note to his translation of Kars ten s Mineralogical Tables he wrote (7, 9,12) .. . but, knowing that chromium also gives by evaporation red or yellow salts, I believe that the brown lead is a yellow oxide of chromium, combined with excess lead also in the form of the yellow oxide. ... 

Dr. Ernst Wittich, German Ambassador to Mexico, pointed out that Baron von Humboldt was also led into the same error, for the specimen in the Museum fur Naturkunde in Berlin is labeled in the Baron s handwriting Brown lead ore from the veins of Zimapin in northern Mexico. Lead chromate. M. del Rio thought he had discovered a new metal in it, which he named erythronium, then panchromium later he realized that it was ordinary chromium. The label was later corrected by Gustav Rose to read Vanadiumbleierz (vanadium lead ore) (29). 

Another circumstance which helped to shake del Rio s confidence in his own work was the analysis of this mineral which H.-V. Collet-Descotils, a friend of Vauquelin, published in 1805 (13). When Collet-Descotils concluded that the supposed new metal was merely chromium, del Rio warmly defended his own prior claim to the discovery of chromium in the brown lead ore (14). 

Test for sulphide dyestuffs. The sample is covered in a test-tube or conical flask with the acid stannous chloride solution, the mouth of the vessel being closed with a piece of filter-paper steeped in lead acetate solution and the liquid heated slowly to boiling. The appearance of a blackish-brown stain on the filter-paper indicates a sulphur dyestuff. The boiling should not be too protracted, since otherwise the hydrochloric acid vapours may cause the brown lead sulphide to disappear. 

Dilute hydrochloric acid Lead (II) acetate or nitrate Cobalt nitrate Mercury Hypochlorites, OCh Yellow coloration, followed by chlorine gas evolution Brown lead (IV) oxide forms upon heating Black precipitate of cobalt (II) hydroxide On shaking slightly acidified solution of a hypochlorite with Hg, a brown precipitate of mercury (II) chloride is formed... 

Lead acetate or lead nitrate solution brown lead dioxide is produced on boiling ... 

SYNS BIOXYDE de PLOMB (FRENCH) C.I. 77580 LEAD BROWN LEAD(TV) OXIDE LEAD OXIDE BROWN LEAD PEROXIDE (DOT) LEAD SUPEROXIDE PEROXYDE de PLOMB (FRENCH)... 

After a reaction, excess lead tetraacetate can be destroyed with ethylene glycol prior to addition of water otherwise brown lead dioxide precipitates. 

Poggendorf (Editor of Ann. Phys. Chem.) added a note to Sefstrom s key article on the discovery of vanadium ] in which he forestalls any allegations regarding the priority of Sefstrom s discovery, in particular with respect to del Rio s claim (which he later withdrew) to have discovered, in 1801-03, a new element in the brown lead ore from Zimapan. 

Lead Dioxide. Lead oxide brown lead peroxide lead superoxide. 02Pb mol wt 239.21. O 13.38%, Pb 36.62%. Occurs in nature as the mineral plattnerite. Lab prepn from lead acetate and calcium hypochlorite Newel], Maxson, Inorg. Syn. 1, 45 ( 939) by hydrolysis of lead acetate Kuhn, Hammer, Ber. 83, 413 (1950). 

Colorless monoclinic prisms From glacial acetic acid. Turns pink easily. Unstable in air. Hydrolyzed by water with the Formation of brown lead dioxide and acetic acid. Avoid contact with skin, dj7 2.228. mp 175-180°. Sol in hot glacial acetic acid, benzene, chloroform, tetrachloroethane, nitrobenzene. Dissolves in coned halogen acids with the formation of haloplumbic acids, H,PbX6. The dry material can be stored in sealed, evacuated ampuls. 

Second thoughts are not always best. On further study of the mineral, del Rio concluded that he was mistaken in assuming the presence of a new element and that the brown lead was merely basic lead chromate. In this he was supported by Collet Descbtils, and there the matter rested for many years. 

Now it so happened that Friedrich Wdhlerj was, at this time, interested in del Rio s brown lead and had found something new in it when he was compelled, by temporary indisposition, due to inhalation of hydrofluoric acid vapour, to set the problem on one side. In 1831 he established the identity of SefstrOm s vanadium... 

Synonyms Cl 77580 Lead brown Lead (IV) oxide Lead oxide brown Lead peroxide Lead superoxide... 

Precaution Unstable in air hydrolysis liberates brown lead dioxide and acetic acid... 

In 1801 del Rio, professor of mineralogy in Mexico City, investigated a brown lead ore from Zimapan and concluded that it contained a new element. Alexander von Humboldt, then visiting Mexico, was given specimens of the ore by del Rio and sent some to the Paris Institut with a letter saying that del... 

Most lead stabilisers have the side effect of making the products opaque, except for the lead carboxylates. They also react with any sulfur present, producing brown lead sulfide. 

Discovery In 1801, A. M. Del Rio in Mexico discovered a new metal in a brown lead ore. He gave the new element the name en/thronium. When confirmation was sought in Europe the metal was said to be chromium and the discovery was not accepted. In 1830, N. G. Sefetrom in Sweden discovered vanadium in iron, manufactured from an ore in Smalands-Taberg. F. Wohler in Germany showed that erythronium and vanadium are in fact identical. Sir Henry Roscoe prepared pure vanadium metal in 1867. His method was reduction of vanadium chloride with hydrogen. 

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