Bright Yellow

NH4)3Moi2PO40 H2O. The bright yellow precipitate formed from a phosphate, am monium molybdate and HNO3 in solution. Used as a test for phosphates. 

Bright yellow needles m.p. 45 C, b.p. 2 4°C. Prepared together with 4-nitrophenol by careful nitration of phenol. Sodium sulphide reduces it to 2-aminophenol which is used in dyestuffs and photographic processes. 

Then filter the remainder of the product at the pump, drain and dry. The glucosazone is thus obtained as bright yellow crystals, m.p. 204° with decomposition. 

Mix 1 g. of quinaldine and 1 g. of powdered />-dimethylaminobenzab dehyde, add 2 -3 drops of 10% etl nolic zinc chloride solution, and heat under reflux in an oil-bath at 150 for 1 hour. Cool the product in ice-water, and reciystallise it from ethanol. p-Dimethylaminostyryl-quinoline (I) separates as bright yellow crystals, m.p. 177-178°. 

Physical Properties. Both solids, freely soluble in hot water, sparingly in cold water. o-Nitrophcnol, bright yellow, volatile in steam, odour resembling both that of phenol and of nitrobenzene />-m trophenol, colourless when pure, non-volatile in steam, odourless. 

Nitrophenol gives similarly a bright yellow coloration with NaOH solution. 

If the m.p. is not quite satisfactory, dissolve the o-nitroplienol in hot alcohol (or methylated spirit) under reflux, add hot water drop by drop until a cloudiness just appears, and allow to cool spontaneously. Filter off the bright yellow crystals and diy between filter paper. 

Triiodobenzoyl chloride. Reflux 5 g. of 3 4 5-triiodo-benzoic acid, m.p. 289-290°, gently with 10 ml. of redistilled thionyl chloride for 2 hours. Distil off the excess of thionyl chloride on a water bath, and recrystallise the residue from carbon tetrachloride - light petroleum with the use of a little decolourising charcoal. The yield of the acid chloride (bright yellow needles, m.p. 138°) is 3-8 g. it keeps well in a stoppered bottle. 

Evaporation of the solvent gave the product as bright yellow crystals (27.6 g) in 74% yield. 

Many hydrazones and azines are colored and useful as dyestuffs. Examples are 2-hydroxynaphthazine, a yellow fluorescent dye (Lumogen LT Bright Yellow), and the pyridon—azino—quinone class of red-violet dyes. Numerous hydrazine derivatives are antioxidants and stabilizers by virtue of their reducing and chelating powers. 

Mercurous Iodide. Mercurous iodide [7783-30 ] Hg2l2, is a bright yellow amorphous powder, extremely insoluble in water and very sensitive to light. It has no commercial importance but may be prepared by precipitation, using mercurous nirate and potassium iodide. Care must be taken to exclude mercuric nitrate, which may cause the formulation of the water-insoluble mercuric iodide. 

Silver iodomercurate [36011-71-9] Ag2HgI, is a bright yellow compound and is prepared similarly to the cuprous salt where silver nitrate is the precipitant. The silver salt, which darkens reversibly at 50°C, is used for the same appHcation as cuprous iodomercurate. 

Silver Phosphates. Silver phosphate [7784-09-0], or silver orthophosphate, Ag3P04, is a bright yellow material formed by treating silver nitrate with a soluble phosphate salt or phosphoric acid. Silver pyrophosphate [13465-97-9], is a white salt prepared by the addition of a soluble... 

Bismuth subgaHate [12552-60-2] (basic bismuth gaHate), Dermatol, is a bright yellow powder that can be prepared by the interaction of bismuth nitrate and gaUic acid in an acetic acid medium. It has been employed as a dusting powder in some skin disorders and as an ingredient of suppositories for the treatment of hemorrhoids (183,185). It has been taken orally for many years by colostomy patients in order to control fecal odors, but the dmg may cause serious neurological problems (186). 

The yellow dye curcumin, [458-37-7] (Cl Natural Ye//oii> 3 Cl 75300) (41), also known as tumeric, occurs in the roots of the plant Curcuma tinctoria found growing wild in Asia. The dye was well known to the ancient Romans and Greeks who used it to dye wool, cotton, and silk. The dye is an oil-soluble bright yellow material, and is the only natural yellow dye that requires no mordant. It finds use as a colorant for baked goods such as cakes. 

C. Thymoquinone.—The wet aminothymol thus prepared is immediately dissolved in no cc. of concentrated sulfuric acid diluted to 4 1. and contained in a 12-I. flask. To this solution is added 150 g. of sodium nitrite (2.18 moles), in 5-10-g. portions, with shaking after each addition. The resulting mixture is heated to 60° on a steam bath, with occasional shaking, for half an hour (Note 5), and is then distilled in a current of steam, by means of the apparatus described in Org. Syn. 2, 80 (Note 6). All the thymoquinone passes over with the first 3 1. of distillate it solidifies on cooling, and is filtered with suction (Note 7), washed, and dried at room temperature. The yield is 80-87 g. (73-80 per cent of the theoretical amount) of bright yellow crystals, melting at 43-45° (Note 8). 

Dissolve in distilled H2O and acidify with dilute HCl to pH 3.5. Filter off the solid acid and wash well with H2O. Redissolve ca lOg in 300mL H2O containing 12g of NaOAc. Ppte again by adding HCl, filter and wash with H2O. Add the solid to 200mL of EtOH stir for Ih and filter. Repeat the EtOH wash and dry the bright yellow solid in a vacuum. This acid decomposes on heating at ca 180°. See below for the prepn of the Na salt. [Anal Chem 28 882 1956]. 

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