Partial decomposition

Fig. 7.34 Dependence of oxygen content in Lai.g5Sro.o5Cu04+ on log P02 at 800... 1000°C. The broken lines represent the decomposition partial pressures. FVomRef. [616].

C with partial decomposition. Synthesized from methanal and ammonia. Hexamine is used as starter fuel for camping stoves, as an... 

The partial wave decomposition of the incident-electron wave provides the basis of an especially appealing picture of strong, low-energy resonant scattering wherein the projectile electron spends a sufficient period of time in the vicinity... 

Wlien the atom-atom or atom-molecule interaction is spherically symmetric in the chaimel vector R, i.e. V(r, R) = V(/-,R), then the orbital / and rotational j angular momenta are each conserved tln-oughout the collision so that an i-partial wave decomposition of the translational wavefiinctions for each value of j is possible. The translational wave is decomposed according to... 

A partial wave decomposition provides the frill close-coupling quantal method for treating A-B collisions, electron-atom, electron-ion or atom-molecule collisions. The method [15] is siumnarized here for the inelastic processes... 

Distillation under Reduced Pressure. Occasionally a liquid, when distillation is attempted under atmospheric pressure, will undergo partial or complete decomposition before its boiling-point is reached. To overcome this difficulty, the liquid is distilled under reduced pressure, so that its boiling-point shall be definitely below its thermal decomposition point. 

The crystalline sodium sulphide (NajS,9H20) used to prepare the disulphide is very deliquescent, and only a sample which has been kept in a well-stoppered bottle and therefore reasonably dry should be used. A sample from a badly-stoppered bottle may contain, in addition to the crystals, a certain amount of aqueous solution, in which hydrolysis and partial decomposition will have occurred such a sample should therefore be rejected. Add 4 2 g. of finely powdered sulphur to a solution of 16 g. of the crystalline sodium sulphide in 60 ml. of water, and boil the mixture gently for a few minutes until a clear solution of the disulphide is obtained. 

Dinitrophenylhydra2ones usually separate in well-formed crystals. These can be filtered at the pump, washed with a diluted sample of the acid in the reagent used, then with water, and then (when the solubility allows) with a small quantity of ethanol the dried specimen is then usually pure. It should, however, be recrystallised from a suitable solvent, a process which can usually be carried out with the dinitrophenylhydrazones of the simpler aldehydes and ketones. Many other hydrazones have a very low solubility in most solvents, and a recrystallisation which involves prolonged boiling with a large volume of solvent may be accompanied by partial decomposition, and with the ultimate deposition of a sample less pure than the above washed, dried and unrecrystal-lised sample. 

Note. The 2,4-dinitrophenylhydrazones of many higher aldehydes and ketones may be insoluble in most solvents. In this case, Mter them off, wash with ethanol, dry and take the m.p. attempted recrystallisation may cause partial decomposition. (M.ps., pp. 530-540.)... 

The benzamide should not be dried in the Steam oven, since it will undergo partial decomposition at 100° into benzonitrile and thus give an impure product of low m.p. 

The physical and chemical properties are less well known for transition metals than for the alkaU metal fluoroborates (Table 4). Most transition-metal fluoroborates are strongly hydrated coordination compounds and are difficult to dry without decomposition. Decomposition frequently occurs during the concentration of solutions for crysta11i2ation. The stabiUty of the metal fluorides accentuates this problem. Loss of HF because of hydrolysis makes the reaction proceed even more rapidly. Even with low temperature vacuum drying to partially solve the decomposition, the dry salt readily absorbs water. The crystalline soflds are generally soluble in water, alcohols, and ketones but only poorly soluble in hydrocarbons and halocarbons. 

Potassium iodate [7758-05-6] KIO, mol wt 214.02, 59.30% I, forms white, odorless crystals or a crystalline powder. It has a density 3.98 g/mL and mp of 560°C with partial decomposition. Potassium iodate is rapidly formed when potassium iodide is fused with potassium chlorate, bromate, or perchlorate. The solubihty in water is 9.16 g/100 g H2O at 25°C and 32.2 g/100 g H2O at 100°C. KIO is extensively used as an oxidizing agent in analytical chemistry and as amaturing agent and dough conditioner (see Bakery processes and leavening agents). 

Anhydrous oxaUc acid normally melts and simultaneously decomposes at 187°C. Sublimation starts at slightly below 100°C and proceeds rapidly at 125°C partial decomposition takes place during sublimation at 157°C. Anhydrous oxaUc acid is hygroscopic and thus absorbs moisture in the air to form the dihydrate. 

When dissolved ia water, the solution is identical with that obtained by dissolving sodium carbonate ia aqueous hydrogen peroxide. There is some evidence for the presence of the traces of tme peroxocarbonate anion, HCO , ia these solutions (95). If the peroxohydrate is heated for about an hour at 100°C and then allowed to cool to room temperature, some decomposition occurs and the product effervesces when placed ia water. Electron spia resonance experiments (64) iadicate that free radicals are present ia this partially decomposed material, but the nature of these radicals is obscure. 

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