Color decomposition

During the reaction the alumina usually attains a pink color which is due to some decomposition of p-tolylsulfonyldiazomethane. However, the colored decomposition products adhere strongly to the alumina and will therefore not contaminate the final product. If the alumina becomes reddish rather than pink, the type of the alumina in use may be too basic, causing more extensive decomposition of the -tolylsulfonyl-diazomethane the reaction time should then be reduced as much as possible to prevent a considerable decrease in yield. 

Very approximately the S2O content of a gas mixture can be estimated from the color of the condensate at -196 °C in a glass trap (provided that all other components are colorless at this temperature). Due to the formation of highly colored decomposition products the condensate is yellow at <2 mol% S2O, orange-yellow at 5-10%, orange at 20-30%, cherry-red at 40-70%, and dark-red at >85% [10]. These colors [14] are caused by small sulfur molecules like S3 and 84 [15, 16] as well as by sulfur radicals formed in the radical-chain polymerization of S2O to polysulfuroxides (S 0)x and SO2 [10, 17] ... 

Methyl Violet Paper, Definite Salmon Color, Decomposition, Compound Minutes Minutes Minutes... 

On long storage, even at the temperature of —80°, nitryl chloride darkens in color. Decomposition is probably accelerated by light. The compound is a corrosive, toxic substance possessing a chlorinelike odor. It attacks organic matter rapidly, sometimes explosively. Its chemical properties have been studied.5,8-10... 

Boiling point (sublimation point) (°C/torr)" Color" Decomposition (ca. "O H-chemical shifts (TMS, ppm)" References... 

Solutions of physostigmine and its salts decompose and eventually become red-colored (13,14). Although methods have been developed (15) which retard the formation of colored decomposition products, those which use antioxidants do not prevent the occurrence of the initial stage of the decomposition, the hydrolytic cleavage of the methylurethane group, to give eseroline (16). 

Confirmation of the structure of the red-colored decomposition product of physostigmine, rubreserine, as the resonance hybrid XXII XXIII in which the zwitterionic mesomeric structure XXIII makes the major contribution, has been obtained (17) by comparison of its UV-, IR-, and PMR-spectra with those of adrenochrome (XXIV XXV). The structures of a further two decomposition products of physostigmine, eserine blue and eserine brown (14,16,18), still remain to be elucidated. 

This nitropropene should be used within a week, or stored in the cold, as the color fades to a slight orange over a couple of weeks in room temperature, which is a sign of decomposition. 

C. Further warming to 65°C forms white iron sulfate monohydrate [17375-41 -6], FeSO H2O, which is stable to 300°C. Strong beating results in decomposition with loss of sulfur dioxide. Solutions of iron(II) sulfate reduce nitrate and nitrite to nitric oxide, whereupon the highly colored [Fe(H20) (N0)] ion is formed. This reaction is the basis of the brown ring text for the quaUtative deterrnination of nitrate or nitrite. 

Pure diketene is stable for several weeks if stored at or below 0°C in an aluminum or stainless steel container. Glass should be avoided because of its inherent basicity which favors slow polymerization. Above 15°C slow decomposition occurs and the color becomes progressively darker. Pressure buHd-up Upon prolonged exposure to heat is possible. Heating and contamination of the container, especiaHy by acids, bases, and water, should be avoided. Residual vapors in empty containers are hazardous and may explode on ignition. 

Stabilizers. Nitro alcohols can be used to prevent the decomposition of phenylenediarnine color-developing agents (27). 2-Hydroxymethyl-2-nitro-l,3-propanediol and 2-nitro-1-butanol have been used as additives for the stabilization of 1,1,1-trichloroethane. 

Analytical and Test Methods. o-Nitrotoluene can be analyzed for purity and isomer content by infrared spectroscopy with an accuracy of about 1%. -Nitrotoluene content can be estimated by the decomposition of the isomeric toluene diazonium chlorides because the ortho and meta isomers decompose more readily than the para isomer. A colorimetric method for determining the content of the various isomers is based on the color which forms when the mononitrotoluenes are dissolved in sulfuric acid (45). From the absorption of the sulfuric acid solution at 436 and 305 nm, the ortho and para isomer content can be deterrnined, and the meta isomer can be obtained by difference. However, this and other colorimetric methods are subject to possible interferences from other aromatic nitro compounds. A titrimetric method, based on the reduction of the nitro group with titanium(III) sulfate or chloride, can be used to determine mononitrotoluenes (32). Chromatographic methods, eg, gas chromatography or high pressure Hquid chromatography, are well suited for the deterrnination of mononitrotoluenes as well as its individual isomers. Freezing points are used commonly as indicators of purity of the various isomers. 

The polymer is exposed to an extensive heat history in this process. Early work on transesterification technology was troubled by thermal—oxidative limitations of the polymer, especially in the presence of the catalyst. More recent work on catalyst systems, more reactive carbonates, and modified processes have improved the process to the point where color and decomposition can be suppressed. One of the key requirements for the transesterification process is the use of clean starting materials. Methods for purification of both BPA and diphenyl carbonate have been developed. 

Pyrotechnic mixtures may also contain additional components that are added to modify the bum rate, enhance the pyrotechnic effect, or serve as a binder to maintain the homogeneity of the blended mixture and provide mechanical strength when the composition is pressed or consoHdated into a tube or other container. These additional components may also function as oxidizers or fuels in the composition, and it can be anticipated that the heat output, bum rate, and ignition sensitivity may all be affected by the addition of another component to a pyrotechnic composition. An example of an additional component is the use of a catalyst, such as iron oxide, to enhance the decomposition rate of ammonium perchlorate. Diatomaceous earth or coarse sawdust may be used to slow up the bum rate of a composition, or magnesium carbonate (an acid neutralizer) may be added to help stabilize mixtures that contain an acid-sensitive component such as potassium chlorate. Binders include such materials as dextrin (partially hydrolyzed starch), various gums, and assorted polymers such as poly(vinyl alcohol), epoxies, and polyesters. Polybutadiene mbber binders are widely used as fuels and binders in the soHd propellant industry. The production of colored flames is enhanced by the presence of chlorine atoms in the pyrotechnic flame, so chlorine donors such as poly(vinyl chloride) or chlorinated mbber are often added to color-producing compositions, where they also serve as fuels. 

The decomposition of dithionite in aqueous solution is accelerated by thiosulfate, polysulfide, and acids. The addition of mineral acid to a dithionite solution produces first a red color which turns yellow on standing subsequentiy, sulfur precipitates and evolution of sulfur dioxide takes place (346). Sodium dithionite is stabilized by sodium polyphosphate, sodium carbonate, and sodium salts of organic acids (347). 

Metallurgical (smelter) plants and spent acid decomposition plants usually produce acid of good (low) color because the SO2 feed gases ate extensively purified prior to use. In some cases, however, and particularly at lead smelters, sufficient amounts of organic flotation agents are volatilized from sulfide ores to form brown or black acid. Such acid can be used in many applications, particularly for fertilizer production, without significant problems arising. 

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