Oranges browning

The tendency of the color to become darker with time is often indicative of chemical degradation. The test is conducted with the aid of a colorimeter (NF T 60-104 and ASTM D 1500) and by comparison with colored glass standards. The scale varies from 0.5 to 8. The French specifications stipulate that diesel fuel color should be less than 5, which corresponds to an orange-brown tint. Generally, commercial products are light yellow with indices from 1 to 2. 

All ammonium salts evolve ammonia on heating with alkali. Ammonia may be delected by (a) its smell, (b) its action in turning red litmus blue and (c) the orange-brown colour produced with Nessler s reagent. This is a very sensitive test. 

Tropeolin O, sodium 2,4-dihydroxyazobenzene-4-sulfonate (indicator) dissolve 0.1 g in 100 mL water pH range yellow 11.0-13.0 orange-brown. 

Methylresorcinol Warm violet-brown Orange-brown... 

Dicobalt octacarbonyl [10210-68-1] M 341.9, m 51 . Orange-brown crystals by recrystn from n-hexane under a carbon monoxide atmosphere [Ojima et al. J Am Chem Soc 109 7714 1987 see also Hileman in Preparative Inorganic Reactions, Jolly Ed. Vol 1 101 1987]. 

At this point there may be a lumpy, dark-brown material mixed with the orange-brown crude precipitated product. There appears to be no need to break up the liunps. 

Naphtholphthalein B = Blue C = Colourless O = Orange OB = Orange-brown Yl IB ... 

Discussion. J. Nessler in 1856 first proposed an alkaline solution of mercury(II) iodide in potassium iodide as a reagent for the colorimetric determination of ammonia. Various modifications of the reagent have since been made. When Nessler s reagent is added to a dilute ammonium salt solution, the liberated ammonia reacts with the reagent fairly rapidly but not instantaneously to form an orange-brown product, which remains in colloidal solution, but flocculates on long standing. The colorimetric comparison must be made before flocculation occurs. 

Nitrate and nitrite ions yield orange-brown to magenta-red chromatogram zones on a pale yellow background immediately on treatment with ammonia these zones are stable for days in an atmosphere of ammonia. 

P = parent ion detected in mass spectrum. Color of complex p-y, pale yellow o, orange o-b, orange-brown c, colorless w, white d-g, deep-green b-g, blue-green r-b, red-brown d-p, dark-purple 1, lemon r, red g, green. H NMR data are available on all the compounds and P NMR on all the Pt-phosphine complexes 231). 

The hydrocarbon salt [28 2 ] dissolves in DMSO without any reaction, giving a deep green solution. In contrast, when this salt is dissolved in chloroform, it affords an orange-brown solution, spectrophotometrically suggesting the formation of a hydrocarbon [28-2]. The formation of the covalent hydrocarbon in chloroform is also supported by the fact that the anion [2 ] is regenerated upon dilution of the freshly prepared solution with 10 volumes of DMSO. 

The reaction is sustained by addition of iron metal which reacts with the sulfuric acid formed, regenerating Fe(n) in solution. To ensure that the desired crystal form precipitates, a seed of a-FeO(OH) is added. However, with appropriate choice of conditions, for example of pH and temperature and by ensuring the presence of appropriate nucleating particles, the precipitation process may be adapted to prepare either the orange-brown y-FeO(OH), the red a-Fe203 or the black Fe304. 

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