Lemon yellow

Fluorescein test paper Is prepared by dipping filter paper into a dilute solution of fluorescein in ethyl alcohol it dries rapidly and is then ready for use. The test paper lias a lemon yellow colour. 

Amorphous Sb2S2 can be prepared by treating an SbQ solution with 442S or with sodium tliiosulfate, or by heating metallic antimony or antimony trioxide with sulfur. Antimony trisulfide is almost iasoluble ia water but dissolves ia concentrated hydrochloric acid or ia excess caustic. In the absence of air, Sb2S2 dissolves ia alkaline sulfide solutions to form the tliioantimonate(III) ion [43049-98-5], SbS 2, in the presence of air the tetratliioantimonate(V) ion [17638-29-8], SbS , is formed. The lemon-yellow crystalline salt, Na SbS 94420, known as Schhppe s salt [1317-86-8], contains the tetrahedral tetratliioantimonate(V) ion. 

The yellow oxides are prepared by precipitating hydrated ferric oxide from a ferrous salt usiag an alkaU, followed by oxidation. The shades obtained range from light lemon yellow to orange, depending on the conditions used for the precipitation and oxidation. Yellow oxides contain about 85% Fe202 and 15% water of hydration. 

Consider Dispersol Yellow B-6G. Dispersol is the Zeneca trade name for its range of disperse dyes for polyester. Therefore, it reveals the manufacturer and the usage. Yellow denotes the main color of the dye. "B" denotes its heatfastness, ie, rather low, and 6G denotes that it is six steps of green away from a neutral yellow, so it is a very greenish yellow, ie, a lemon yellow. 

The sodamide must be free from sodium hydroxide and may be conveniently weighed under the 250 cc. of purified mineral oil which is used to rinse out the mortar. Care must be exercised in the use of old sodamide as it sometimes contains an explosive compound that might cause trouble. The nature of this explosive compound is not definitely known however, it appears to be associated with the development of a lemon yellow color. Should any part of the sodamide develop this color it is recommended that the whole be destroyed at once. 

This material Is purified by recrystallization from ethyl acetate acetone 2 1 (v v) to give a first crop (6.8 g), and by flash chromatography of the residue from the mother liquor, using 150 g of 230-400 mesh silica gel (Merck), a 40-mm diameter column, and elution with 10 1 (v v) ethyl acetate methanol. A fast moving orange band and a slower moving lemon-yellow band can be clearly seen on the column. The lemon-yellow hand is collected from the column and evaporation gives a second crop (1.4 g) of comparably pure material. The total yield of the pale yellow isoquinoline is 8.2 g (86t), mp 135-137°C (Note 10). 

Calcium hexacyanoferrate (II) (IIH2O) [ 13821 -08-4] M 490.3. Recrystd three times from conductivity H2O and air dried to constant weight over partially dehydrated salt. [Trans Faraday Soc 45 855 1949.] Alternatively the Ca salt can be purified by pptn with absolute EtOH in the cold (to avoid oxidation) from an air-free saturated aqueous soln. The pure lemon yellow crystals are centrifuged, dried in a vacuum desiccator first over dry charcoal for 24h, then over partly dehydrated salt and stored in a dark glass stoppered bottle. No deterioration occurred after 18 months. No trace of Na, K or NH4 ions could be detected in the salt from the residue after decomposition of the salt with cone H2SO4. Analyses indicate 1 Imols of H2O per mol of salt. The solubility in H2O is 36.45g (24.9 ) and 64.7g (44.7 ) per lOOg of solution. [J Chem Soc 50 1926.]... 

Gold (I) cyanide [506-65-0] M 223.0, m dec on heating. The lemon yellow powder is sparingly soluble in H2O and EtOH but soluble in aqueous NH3. It is obtained by heating H[Au(CN)2] at 110°. Wash well with H2O and EtOH and dry at 110°. It has an IR band at v 2239cm typical fo C=N stretching vibration. [Handbook of Preparative Inorg anic Chemistry (Ed. Brauer) Vol II 1064 7965.] CARE may evolve HCN. 

Vanadyl trichloride (VOCI3) [7727-18-6] M 173.3, m-79.5°, b 124.5-125.5°/744mm, 127.16°/760mm, d 1.854, d 1.811. Should be lemon yellow in colour. If red it may contain VCI4 and CI2. Fractionally distil and then redistil over metallic Na but be careful to leave some residue because the residue can become EXPLOSIVE in the presence of the metal USE A SAFETY SHIELD and avoid contact with moisture. It readily hydrolyses to vanadic acid and HCl. Store in a tightly closed container or in sealed ampoules under N2. [Inorg Synth 1 106 1939, 4 80 1953.]... 

The product is collected on a suction filter. The yield of air-dried product, as yellow-orange crystals, m.p. 87-89°, is 38-42 g. (65-71%) (Note 8). A purer, lemon-yellow product, m.p. 88.5-90°, is obtained by an additional recrystallization from 1 1. of petroleum ether (b.p. 90-100°) with use of carbon the yield after this second crystallization is 28-34 g. (48-58%). 

Observable Characteristics - Physical State (as normally shipped) Liquid Color Lemon yellow Odor Acrid. 

Organic acids yield lemon-yellow zones on a blue background [1]. Halide ions migrate as ammonium salts in ammoniacal mobile phases and are also colored yellow. The colors fade rapidly in the air. This can be delayed for some days by covering the chromatogram with a glass plate. 

The ternary Ge halides, MGeX3 (M = Rb, Cs X = Cl, Br, I) are polymorphic with various distorted perovskite-like (p. 963) structures which reflect the influence of the nonbonding pair of electrons on the Ge" centre. Thus, at room temperature, rhombohedral CsGel3 has three Ge-I at 275 pm and three at 327 pm whereas in the high-temperature cubic form (above 277°C) there are six Ge-I distances at 320 pm as a result of position changes of the Ge atoms (reversible order-disorder transition). Again, RbGel3 has a lemon-yellow, orthorhombic form below —92° an intermediate, bordeaux-red orthorhombic perovskite form (—92° to —52°) a black rhombohedral form (—52° to —29°) and... 

Preparation of 2-Hydroxy-4,4 -Dicyanostilbene 10 grams of 2-amino-4,4 -dicyanostilbene thus prepared were dissolved in 400 cc of boiling glacial acetic acid and 200 cc of dilute sulfuric acid added the solution was suddenly chilled and diazotized over one and a half hours at 5° to 10°C with sodium nitrate (3.0 grams/15 cc H O). The diazonium salt solution was decomposed by boiling for 15 minutes with 600 cc of 55% aqueous sulfuric acid solution the solution was diluted, cooled and filtered. The residue crystallized from ethyl alcohol as lemon yellow prismatic needles, MP 296°C. 

Xylenolorange. This indicator is 3,3 -bis[ IV,/V-di(carboxy methyl Jaminomethyl]-o-cresolsulphonphthalein it retains the acid-base properties of cresol red and displays metal indicator properties even in acid solution (pH = 3-5). Acidic solutions of the indicator are coloured lemon-yellow and those of the metal complexes intensely red. 

Use of tartrazine as indicator. Satisfactory results may be obtained by the use of tartrazine as indicator. Proceed as above, but add 4 drops of tartrazine (0.5 per cent aqueous solution) in lieu of the iron(III) indicator. The precipitate will appear pale yellow during the titration, but the supernatant liquid (best viewed by placing the eye at the level of the liquid and looking through it) is colourless. At the end point, the supernatant liquid assumes a bright lemon-yellow colour. The titration is sharp to one drop of 0.1 M thiocyanate solution. 

Procedure C. Pipette 25 mL of the diluted solution into a 250 mL conical flask containing 5mL of 6M nitric acid, add a slight excess of 0.1M silver nitrate (30-35 mL) from a burette, and four drops of tartrazine indicator (0.5 per cent aqueous solution). Shake the suspension for about a minute in order to ensure that the indicator is adsorbed on the precipitate as far as possible. Titrate the residual silver nitrate with standard 0.1 M ammonium or potassium thiocyanate with swirling of the suspension until the very pale yellow supernatant liquid (viewed with the eye at the level of the liquid) assumes a rich lemon-yellow colour. 

Aerial oxidation of Ru(H20)g+ produces lemon-yellow Ru(H20) + (Ru-O 2.029 A in the tosylate salt)... 

In a dry, 1-1., two-necked flask, equipped with a mechanical stirrer and a reflux condenser fitted with a drying tube, are placed 17.8 g. (0.100 mole) of anthracene (Note 1), 27.2 g. (0.202 mole) of anhydrous cupric chloride (Note 2), and 500 ml. of carbon tetrachloride (Note 3). The reaction mixture is stirred and heated under reflux for 18-24 hours. The brown cupric chloride is gradually converted to white cuprous chloride, and hydrogen chloride is gradually evolved. At the end of the reaction the cuprous chloride is removed by filtration, and the carbon tetrachloride solution is passed through a 35-mm. chromatographic column filled with 200 g. of alumina (Note 4). The column is eluted with 400 ml. of carbon tetrachloride. The combined eluates are evaporated to dryness to give 19-21 g. (89-99%) of 9-chloroanthracene as a lemon-yellow solid, m.p. 102-104° (Note 5). Crystallization of the product from petroleum ether... 

JV,N, ]V"-triphenylguanidine reacts with Ru(02CCp3)2(C0)(PPh3)2 in boiling toluene to yield the lemon-yellow bis(guanidinate) complex... 

If the order of application of the reagents is reversed and all other conditions kept the same, lemon-yellow chromatogram zones are produced on a pale yellow background. 

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