Chrome yellow, precipitation

ZnS04 7HgO) in 50 ml. of HgO. The chrome yellow precipitate is washed several times by centrifugation with hot water. It is dried at 80°C, then at 100°C the orange product is ground. It contains about 6% free S, which is extracted in a Soxhlet apparatus with CSg. 

According to Kiilm and Curran (1986), during the nineteenth century Baltimore chrome yellow was likely to have contained calcium sulfate and lead sulfate (qq.v.), or, according to Mierzinski (1881), alum (hydrous potassium aluminium sulfate, KA1[S04]2.12H20). They state that the term is now applied to a pale chrome yellow precipitated on gypsum or asbestine (q.v.). 

Chrome yellow pigment is made up of lead chromate, and it is formed as a precipitate of the reaction involving lead nitrate, caustic soda, and sodium dichromate. The precipitate is filtered, treated with... 

Chrome green is produced by mechanically mixing chrome yellow and iron blue pigments in water. An iron blue, [Fe(NH4) (FeCN6)], is an oxidized precipitate product of the reaction between an aqueous solution of iron sulfate and ammonium sulfate with sodium hexacyanoferrate. 

I he precipitation of lead(II) chromate is used to estimate lead gravimetrically the yellow precipitate of lead(II) chromate is filtered off. dried and weighed. Lead(II) chromate is used as a pigment under the name chrome yellow . 

Chromate of Lead—TbO, Or Of—chrome yellow.— When chromate of potassa is added to a soluble salt of lead, both solutions being hot, a fine colored anhydrous precipitate is obtained if the solutions are cold, tho precipitate wilt bo pale yellow, and will contain an equivalent of water. 

The chrome yellow pigments [4344-37-2], C.I. Pigment Yellow 34 77600 and 77603, are pure lead chromate or mixed-phase pigments with the general formula Pb(Cr,S)04 [3.131] (refractive index 2.3-2.65, density ca. 6 g/cm3). Chrome yellow is insoluble in water. Solubility in acids and alkalis and discoloration by hydrogen sulfide and sulfur dioxide can be reduced to a minimum by precipitating inert metal oxides on the pigment particles. 

Carefully controlled precipitation and stabilization provide chrome yellow pigments with exceptional fastness to light and weathering, and very high resistance to chemical attack and temperature, enabling them to be used in a wide field of applications. The following qualities are commercially available ... 

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. 

Yellow ochre may be " improved, besides by artificial organic dyes, also by vegetable colours or by chrome yellow. These are detected by treatment with sodium hydroxide from the alkaline solution of vegetable colours, the corresponding lakes are precipitated by addition of aluminium sulphate the same alkaline solution, acidified with acetic acid, gives a yellow precipitate in presence of chrome yellow. 

A little of the substance is treated with hot dilute hydrochloric add any insoluble residue remaining may contain especially barium sulphate or free sulphur, and sometimes cinnabar, arsenic sulphide, etc. If the hydrochloric acid solution is coloured, chrome yellow may be present and is easily identified. The solution gives a yellow precipitate with hydrogen sulphide if the filtrate is rendered turbid by addition of ammonia and ammonium sulphide, zinc is present. 

Precipitation conditions determine crystal structure. Lemon chrome yellows are precipitated hot with excess lead to form the monclinic crystal. Primrose yellow is preciptated at a lower temperature to form the orthorhombic crystal. Chrome oranges are precipitated under alkaline conditions. The higher the alkalinity, the larger the particle. The precipitation of molybdate orange is complicated by the polymorphic nature of two of the components of the solid solution precipitate lead chromate and lead sulfate. As with primrose yellow, the crystal is stabilized after precipitation to prevent conversion. 

Chrome yellow is insoluble in water. Solubility in acids and alkalis and discoloration by hydrogen sulfide and sulfur dioxide can be reduced to a minimum by precipitating inert metal oxides on the pigment particles. 

Insoluble chromates such as Ag2Cr04, BaCr04 and PbCr04 are, however, precipitated from acid solution, the last named being an important pigment, chrome yellow. 

By far the most important products are chrome yellow and molybdate red. The chrome yellow pigments are Pb(Cr,S)04 mixed phases or pure PbCr04 and are produced by precipitation from the aqueous phase. The different hues from green-tinged yellow to bright and mid-yellow to golden yellow can be controlled by the crystal modification (orthorhombic or monoclinic) or by varying the lead sulfate content. 

Lead(II) chromate, PbCr04, is a yellow paint pigment (called chrome yellow) prepared by a precipitation reaction (Figure 3.4). In a preparation, 45.6 g of lead(II) chromate is obtained as a precipitate. How many moles of PbCr04 is this ... 

Leaden) chromate, PhCr04, was used as a yellow paint pigment ( chrome yellow ). When a solution is prepared that is 5.0 X 10 Af in lead ion, Pb ", and 5.0 X 10 Af in chromate ion, Cr04 , would you expect some of the lead(n) chromate to precipitate See Table 18.1. 

The yellow paint pigment chrome yellow is produced by a precipitation reaction. Write an equation in which chrome yellow is produced from lead(II) nitrate. 

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