Citron yellow

Chelerythrine crystallises from alcohol in colourless, prismatic leaflets, m.p. 207°, containing one molecule of alcohol. The alkaloid absorbs carbon dioxide from the air, becoming yellow. The solutions fluoresce blue when the alkaloid is contaminated with its oxidation product, which is formed by mere exposure of solutions to air. The salts, which are quaternary, are intensely yellow. The hydrochloride, B. HCl. HjO, forms citron-yellow needles, and the sulphate, B. H2SO4.2HjO, golden-yellow needles, sparingly soluble in water the platinichloride, B2. HaPtCl. ... 

Zinc oxide reacts with potassium dichromate in solution in the presence of sulfuric acid to form a greenish-yellow pigment, zinc yellow or citron yellow [11103-86-9], 4ZnO dCrOs K2O 3H2O... 

Tellurium JVitride. Tellurium nitride [12164-01-0], TegN is an unstable, citron-yellow solid that detonates easily when heated or struck, but it can be kept under dry chloroform. It is said to explode on contact with water, possibly because of the heat of wetting. 

Chlorine and iodine.—In the course of his historic research on iodine, J. L. Gay Lussac (1814) 6 prepared a compound of iodine and chlorine by the action of chlorine gas on iodine—the gas was absorbed by the solid forming a reddish-brown liquid which is so remarkably like bromine, that before that element had been recognized as a distinct chemical individual by A. J. Balard, J. von Liebig mistook bromine for iodine chloride. If the chlorine be in excess, citron-yellow needle-like crystals are formed. The liquid product is iodine monochloride the crystalline solid is iodine trichloride. H. Davy called the product formed by the action of iodine on chlorine, olilorionio acid, and he regarded it as a compound consisting of one proportion of iodine and one of chlorine —i.e. iodine monochloride. 

Iodine trichloride.—This compound was discovered by J. L. Gay Lussac as the result of treating warm iodine or iodine monochloride with an excess of chlorine. The trichloride collects as a citron-yellow crystalline sublimate on the cooler parts of the vessel. It is also formed by the action of liquid chlorine on iodine, or an iodide—say lead iodide.18 The iodine trichloride is almost insoluble in liquid chlorine, and hence, say Y. Thomas and P. Dupuis, this method of preparation is very convenient. It is also formed by the action of dry chlorine on hydrogen iodide (A. Christomanos) silver iodate (J. Krutwig) or methyl iodide (L. von... 

Iodine trichloride forms long citron-yellow needles, and also large reddish-brown rhombic plates. The sp. gr. at 15° is 3T17 (A. Christomanos). This compound melts in a sealed tube under the press, of its own vapour at 101° and 16 atm. press, forming a reddish-brown liquid which freezes to crystals of the same colour. The citron-yellow crystals are obtained by sublimation. The differences in colour and appearance led W. Stortenbeker to say that the trichloride is dimorphous. The crystals readily decompose in air, but they can be preserved unchanged in an atm. 

Aluminium and magnesium selenides are very similar light brown powders, unstable in air. Zinc and iron (ferrous) selenides are more stable in air, the zinc compound being citron-yellow and the iron compound black and metallic in appearance.8 The latter becomes brown in air owing to oxidation. Ferric selenide is difficult to obtain pure. Cadmium selenide, which is dark brown, is very stable in colour and is used as a pigment. With thallium, selenium is said to form three distinct compounds,9 but analyses of these compounds have led to discordant results. The selenides of aluminium, chromium and uranium cannot be prepared in the wet way. Nickel selenide, unlike the sulphide, shows no tendency to form a colloidal solution. 

Citron-yellow, tabular crystals, which are quite permanent in the air and are soluble in 4 parts of cold, and 2 parts of boiling, water insoluble in alcohol. 

Mercuric Orthoarsenate, Hg8(As04)2, is obtained by precipitating a solution of mercuric nitrate with a solution of sodium mono- or dihydrogen arsenate, or by dropping aqueous arsenic acid into excess of mercuric nitrate solution.4 It is a heavy citron-yellow powder. Hot water dissolves it slightly without decomposition, and shining crystals may separate from the cooled solution. Hydrochloric acid dissolves it freely, nitric acid less readily, and arsenic acid not at all. Brine solution converts it into red-brown mercury oxychloride. Potassium bromide solution colours it brown, and a yellow residue is ultimately left. Potassium iodide forms mercuric iodide. 

Diethyl selenium dibromide, (C2H5)2SeBr2, is a heavy, citron-yellow oil. 

This compound 2 has already been described on p. 21. It is characterised by its silver salt, a bright red powder, its lead salt, an orange-coloured powder, its copper salt, a pale brown powder, and its mercury salt9 a citron-yellow powder. 

Ammonium molybdate in nitrie acid Citron-yellow pp. Nil. Nil. 

Basic Rhodium Sulphate.—When the neutral rhodium sulphate is boiled with excess of water until the wash waters are not appreciably coloured, and cease to be acid towards indicators, a citron-yellow powder is obtained, insoluble in water. This is a basic sulphate, for which the formula Rh203.RhE(S04)3 is given by Leidie.1... 

SYNS BUTTERCUP YELLOW CHROMIC ACID, POTASSIUM ZINC SALT (2 2 1) CITRON YELLOW POTASSIUM ZINC CHROMATE ZINC CHROME ZINC YELLOW... 

Basic uranyl sulphates of composition 8U2O3.SO3.2H2O and 4U2O3. SO3.7H2O have been obtained by evaporating at 250 C. solutions of uranyl sulphate containing 3 and 15 per cent, respectively. The former yields citron-yellow, and the latter greyish-yellow, microscopic crystals. 

Tetraethylarsonium bromide forms a deli<(uescent, crystalline mass, very soluble in water anbismuth bromide it yit lds 3(C2n5)4AsBr.2BiBrg, which crystallises in citron yellow crystals. 

Chloro-l 4-arsenobenzene or 2 2 -dichloro-l 4 1 4 -diarsenodibenzene results when the previous ehloro-diarsinic acid is reduced by hypophosphorous acid. It is an amorphous, citron-yellow powder, insoluble in all solvents. On boiling with concentrated hydrochloric or sulphuric acid, or with amyl alcohol, it loses its colour. 

The acid is soluble in hot water and the usual solvents, insoluble in ether. Its diazo-compound is citron-yellow and gives a red dye with alkaline resorcinol. The sodium salt forms glistening groups of silver crystals containing 5 molecules of water. en carbonyl chloride is passed into a solution of tlie arsinic acid in aqueous sodium acetate, a white crystalline product is obtained. ... 

Tin di-cyciohexyl is aii intense yellow, odourless powder, very easily soluble in benzene, soluble in ether, and insoluble in absolute alcohol. In very dilute benzene solution it is citron yellow. When heated in absence of air it becomes deep orange-yellow at 130" C., and melts to a ruby red liquid at 176" to 178" C., darkening at 260° C., and decomposing at 285" C. 

Technical morin (3,5,7,2, 4 -pentahydroxyflavone) is supplied by Eastman, Baker, and Matheson, Coleman and Bell. A solution of 300 n of morin in 500 ml. of methanol is added with stirring to a slurry of 500 g. of alumina in 500 ml. of methanol. When the supernatant liquor is decolorized, the alumina is collected and dried at 150° for 2 hrs., when the citron-yellow preparation has grade II activity." A column of this adsorbent fluoresces in ultraviolet light (ca. 360 m/r), and colorless substances that absorb in the near ultraviolet show up on the column as dark bands on a luminous background. It proved useful for separation of naturally occurring polyunsaturated diols."... 

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