Suspensions decomposition

The evolution of nitrogen is not always entirely satisfactory as a test owing to the possible evolution of gaseous decomposition products of nitrous acid itself. The test may be performed as follows. To i ml. of chilled concentrated sodium nitrite solution add i ml. of dilute acetic acid. Allow any preliminary evolution of gas to subside, and then add the mixed solution to a cold aqueous solution (or suspension) of the amide note the brisk effervescence. 

Action of nitrous acid. To a few ml. of 20% NaNO, solution add a few drops of cold dil. acetic acid. Pour the mixture into a cold aqueous solution of glycine, and note the brisk evolution of nitrogen. NH CH COOH -h HNO2 = HO CH2COOH + N + H O. Owing to the insolubility of cystine in acetic acid use a suspension in dU. acetic acid for this test. In each case care must be taken not to confuse the evolution of nitrogen with any possible thermal decomposition of the nitrous acid cf. footnote, p, 360). 

Azobisnittiles are efficient sources of free radicals for vinyl polymerizations and chain reactions, eg, chlorinations (see Initiators). These compounds decompose in a variety of solvents at nearly first-order rates to give free radicals with no evidence of induced chain decomposition. They can be used in bulk, solution, and suspension polymerizations, and because no oxygenated residues are produced, they are suitable for use in pigmented or dyed systems that may be susceptible to oxidative degradation. 

Bina Selenides. Most biaary selenides are formed by beating selenium ia the presence of the element, reduction of selenites or selenates with carbon or hydrogen, and double decomposition of heavy-metal salts ia aqueous solution or suspension with a soluble selenide salt, eg, Na2Se or (NH 2S [66455-76-3]. Atmospheric oxygen oxidizes the selenides more rapidly than the corresponding sulfides and more slowly than the teUurides. Selenides of the alkah, alkaline-earth metals, and lanthanum elements are water soluble and readily hydrolyzed. Heavy-metal selenides are iasoluble ia water. Polyselenides form when selenium reacts with alkah metals dissolved ia hquid ammonia. Metal (M) hydrogen selenides of the M HSe type are known. Some heavy-metal selenides show important and useful electric, photoelectric, photo-optical, and semiconductor properties. Ferroselenium and nickel selenide are made by sintering a mixture of selenium and metal powder. 

Product Quality Considerations of product quahty may require low holdup time and low-temperature operation to avoid thermal degradation. The low holdup time eliminates some types of evaporators, and some types are also eliminated because of poor heat-transfer charac teristics at low temperature. Product quality may also dic tate special materials of construction to avoid met hc contamination or a catalytic effect on decomposition of the product. Corrosion may also influence evaporator selection, since the advantages of evaporators having high heat-transfer coefficients are more apparent when expensive materials of construction are indicated. Corrosion and erosion are frequently more severe in evaporators than in other types of equipment because of the high hquid and vapor velocities used, the frequent presence of sohds in suspension, and the necessary concentration differences. 

Chemical Additives The use of chemical additives in sink-float processing is not common except for the use of lime to prevent oxidation and decomposition of the medium. A small amount of clay is sometimes added to improve the kinetic stability of the suspension. 

HCIO2 is formed (together with HCIO3) during the decomposition of aqueous solutions of CIO2 (p. 847) but the best laboratory preparation is to treat an aqueous suspension of Ba(C102)2 with... 

To a suspension of 3.0 g of 7-[D-(-)-a-amino-p-hydroxyphenylacetamido] -3-[5-(1-methyl-1,2,3,4-tetrazolyl)thiomethyl] -A3arboxylic acid in 29 ml of water was added 0.95 g of anhydrous potassium carbonate. After the solution was formed, 15 ml of ethyl acetate was added to the solution, and 1.35 g of 4-ethyl-2,3-dioxo-1 -piperazinocarbonyl chloride was added to the resulting solution at 0°C to 5°C over a period of 15 minutes, and then the mixture was reacted at 0°C to 5°C for 30 minutes. After the reaction, an aqueous layer was separated off, 40 ml of ethyl acetate and 10 ml of acetone were added to the aqueous layer, and then the resulting solution was adjusted to a pH of 2.0 by addition of dilute hydrochloric acid. Thereafter, an organic layer was separated off, the organic layer was washed two times with 10 ml of water, dried over anhydrous magnesium sulfate, and the solvent was removed by distillation under reduced pressure. The residue was dissolved in 10 mi of acetone, and 60 ml of 2-propanol was added to the solution to deposit crystals. The deposited crystals were collected by filtration, washed with 2-propanol, and then dried to obtain 3.27 g of 7-[D-(-)-a-(4-ethyl-2,3-dioxo)-1 -piperazinocarbonylamino)-p-hydroxyphenylacetamido] -3-[5-(1 -methyl-1,2,3,4-tetrazolyl)thiomethyl]-A product forms crystals, MP 1BB°C to 190°C (with decomposition). 

D/chloro-5-Cyclohexyl-2-Oxo-2,3-D/hydro 1 H-Benzo(fj-Diazepine-1,4 fa) Process Using Sodium Hypochlorite — 40 ml of a solution of sodium hypochlorite of 14.5 British chloro-metric degrees are added to a suspension of 5.4 grams of 7 chloro-5 cyclohexyl-2 oxo-2,3-dihydro 1 H-benzo(f)diazepine-1,4 in BO ml of methylene chloride. The mixture is stirred at room temperature for 15 minutes the solid dissolves rapidly. The organic iayer is decanted, washed with water, dried over anhydrous Sodium sulfate and the solvent evaporated under reduced pressure without exceeding a temperature of 30 C. The residue is taken up in a little diisopropyl ether and the crystals which form are dried. They are recrystallized as rapidly as possible from ethyl acetate. Colorless crystals are obtained (3.9 grams yield, B5%) MP < = 163°C, with decomposition. 

The decomposition of an initiator seldom produces a quantitative yield of initiating radicals. Most thermal and photochemical initiators generate radicals in pairs. The self-reaction of these radicals is often the major pathway for the direct conversion of primary radicals to non-radical products in solution, bulk or suspension polymerization. This cage reaction is substantial even in bulk polymerization at low conversion when the medium is essentially monomer. The importance of the process depends on the rate of diffusion of these species away from one another. 

One of the first reports involving vinyl diazonium ions and possible vinyl cations is the work of Newman and co-workers (107) on the alkaline decomposition of 3-nitroso-2-oxazolidones, 132. When an aqueous suspension or... 

In contrast to other organothallium(I) compounds, cyclopentadienyl-thallium(I) is a remarkably stable compound. Samples can be stored in sealed bottles for months without appreciable decomposition occurring it is unaffected by water and dilute alkali and it is only slowly oxidized by air at room temperature. Cyclopentadienyltballium(I) was first prepared by Meister in 1956 by addition of freshly distilled cyclopentadiene to a suspension of thallium(I) sulfate in dilute potassium hydroxide solution 101, 102). A number of variations of this procedure have been described (5, 25, 34, 56), and the compound has been made in other ways 35, 56,110, 164), but Meister s preparation, in which the yield of crude product is greater than 90%, remains the method of choice. Purification of crude cyclopenta-dienylthallium(I) is best accomplished by vacuum sublimation, and purity of samples can readily be assessed by gas-liquid chromatography on silicone oil at 170° C using hydrogen as carrier gas (7). 

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