Basic Lead Chromate

Lead (II) chromate Lead (IV) chromate Lead chromate (VI). See Lead chromate Lead chromate, basic. See Lead chromate oxide... 

Chromium lead oxide Chromium orange Cl 77601 Indian red Lead chromate, basic Lead chromate (VI) oxide Lead chromate, red Light orange chrome Orange chrome Persian red... 

Basic lead silico chromate n. Calcined basic lead chromate - basic lead sihcate complex on a silica core, used as a corrosion-inhibiting pigment. Sp gr of 4.1 particle size of 7pm O.A. of 10-18g/100g CrOs -5.4wt.% Si02 - 47.6wt.% PbO -47.0wt.% (Gooch 1993). 

The basic compositions of the most common commercially available lead chromate pigments are given ia Table 2 (44). 

Lead chromates are prepared by precipitation techniques from soluble salts ia aqueous media. The raw material Hst iacludes a number of different lead compounds, eg, Htharge, lead nitrate, basic lead acetate, basic lead carbonate, as well as acids, alkahes, sodium bichromate, and sodium chromate. The typical reaction can be represented by the foUowiag equation ... 

Basic lead silicochromate [11113-70-5] (National Lead Co. designation Pigment M-50) is a composite in which basic lead chromate, ie, chrome orange, is precipitated onto a lead siUcate—siUca base. It does not have an appreciable chromate solubiUty and depends on lead oxide for its effectiveness. 

A. M. del Rio in 1801 claimed to have discovered the previously unknown element 23 in a sample of Mexican lead ore and, because of the red colour of the salts produced by acidification, he called it erythronium. Unfortunately he withdrew his claim when, 4 years later, it was (incorrectly) suggested by the Frenchman, H. V. Collett-Desotils, that the mineral was actually basic lead chromate. In 1830 the element was rediscovered by N. G. Sefstrom in some Swedish iron ore. Because of the richness and variety of colours found in its compounds he called it vanadium after Vanadis, the Scandinavian goddess of beauty. One year later F. Wohler established the identity of vanadium and erythro-nium. The metal itself was isolated in a reasonably pure form in 1867 by H. E. Roscoe who reduced the chloride with hydrogen, and he was... 

Soluble pigments The most important pigments in this class are the metallic chromates, which range in solubilities from 17 0 to 0-00005 g/1 CrO . An examination has recently been carried out of the mechanism of inhibition by chromate ions and it has been shown by chemical analysis of the stripped film, Mdssbauer spectroscopy and electron microprobe analysis that the air-formed film is reinforced with a more protective material in the form of a chromium-containing spinel (Chapter 17). The situation is, however, complicated by the possibility that some chromates, particularly the basic ones, may inhibit through the formation of soaps. There is evidence that lead chromate can function in this way. 

Persian red inorg chem Red pigment made from basic lead chromate or ferric oxide. por-zhon red ... 

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. 

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. 

Prepare about 30 g. of normal lead chromate, PbCr04 (Exercise 23), by the double decomposition of lead acetate and potassium dichromate and wash the precipitate until it is free from soluble lead salts. Suspend the yellow chromate in a dilute solution of sodium hydroxide (1 20) and boil until the color has changed to a bright brick red. This material is a basic chromate known as chrome red, having the composition represented by the formula PbCr04-PbO ... 

Chrome orange [1344-38-3], C.I. Pigment Orange 21 77601, is a basic lead chromate with the composition PbCr04 PbO but is no longer of technical or economic importance. 

The product is heated in a rotary kiln causing the excess lead oxide to react with the basic lead chromate, forming tetrabasic lead chromate ... 

Chromates. Lead eliminate, "chrome yellow" PhCrOj. yellow precipitate. by reaction of soluble lead salt solution and sodium dieltromaie or chromate solution, inching point ol lead chromate S44 C. Used as a pigment basic lead chromate, red solid, insoluble, formed by healing lead chromate and sodium hydroxide solution. 

The principal red and yellow pigments are Lead chromate chrome yellow, orange and red), zinc chromate zinc or buttercup yellow), barium chromate lemon yellow or yellow ultramarine) various products based on jerric oxide, hydrated (yellow) or anhydrous (red), both natural yellow and red ochres) and artificial Mars yellow, English red, etc.) red oxide oj lead minium or red lead) mercuric sulphide cinnabar, vermilion) antimony oxysulphide antimony cinnabar) cadmium sulphide cadmium yellow) basic lead antimonate Naples yellow). 

These are based on lead chromate and exhibit all gradations in colour from pale yellow to gamet red, but they may be referred to three principal types chrome yellow, normal lead chromate chrome orange, mixture of normal and basic lead chromates chrome red, basic lead chromate. 

Chrome red Basic lead chromate Pb20Cr04 Paint pigment... 

Basic lead chromate [PbCr04 Pb(0H)2] may be used as an orange-red pigment it is an excellent corrosion inhibitor. It is manufactured by boiling white lead (PbC03) with a solution of sodium dichromate. 

Molybdenum salts used as catalysts include cobalt molybdate for hydrogen treatment of petroleum stocks for desulfurization, and phospho-molybdates to promote oxidation. Compounds used for dyes are sodium, potassium, and ammonium molybdates. With basic dyes, phosphomolyb-dic acid is employed. The pigment known as molybdenum orange is a mixed crystal of lead chromate and lead molybdate. Sodium molybdate, or molybdic oxide, is added to fertilizers as a beneficial trace element. Zinc and calcium molybdate serve as inhibitory pigments in protective coatings arid paint for metals subjected to a corrosive atmosphere. Compounds used to produce better adherence of enamels are molybdenum trioxide and ammonium, sodium, calcium, barium, and lead molybdates. 

Chromium metal is commercially produced in the United States by the reduction of chromite ore with carbon, aluminum, or silicon, and subsequent purification. Sodium chromate and dichromate are produced by roasting chromite ore with soda ash. Most other chromium compounds are produced from sodium chromate and dichromate (Hartford 1979 Westbrook 1979). For example, basic chromic sulfate (Cr(0H)S04), commonly used in tanning, is commercially produced by the reduction of sodium dichromate with organic compounds (e.g., molasses) in the presence of sulfuric acid or by the reduction of dichromate with sulfur dioxide. Lead chromate, commonly used as a pigment, is produced by the reaction of sodium chromate with lead nitrate or by reaction of lead monoxide with chromic acid solution (IARC 1990). 

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