Over-heating

Butene, a-bulylene, CH3CH2CH CH2-Prepared by passing the vapour of 1-butanol over heated alumina. 

Colourless liquid b.p. 69 5 C. Manufactured from propanone by conversion to pinacone and passing its vapour over heated KHSO4. Slowly changes to a rubber-like substance the change is hastened by metallic sodium or peroxides. Used in the manufacture of artificial rubber. 

Aluminium chloride can be prepared not only by the direct combination of the elements but also by the passage of dry hydrogen chloride over heated aluminium ... 

Germanium forms divalent compounds with all the halogens. Germaniunil 1) chloride can be prepared by passing the vapour of germanium(IV) chloride (see below) over heated germanium. The reaction is reversible and disproportionation of germanium(II) chloride is complete at about 720 K at atmospheric pressure ... 

Reduction products vary depending on the reducing agent, for example dinitrogen oxide is obtained with sulphurous acid, nitrogen is obtained when the gas is passed over heated metals (e.g. copper and iron) and ammonia is produced when the gas reacts with aqueous chromiumfll) salts. 

However, if heated hydrogen chloride is passed over heated metals, the chloride is formed in the case of a metal exhibiting variable oxidation state, the lower chloride is obtained ... 

As a result of the development of electronic applications for NF, higher purities of NF have been required, and considerable work has been done to improve the existing manufacturing and purification processes (29). N2F2 is removed by pyrolysis over heated metal (30) or metal fluoride (31). This purification step is carried out at temperatures between 200—300°C which is below the temperature at which NF is converted to N2F4. Moisture, N2O, and CO2 are removed by adsorption on 2eohtes (29,32). The removal of CF from NF, a particularly difficult separation owing to the similar physical and chemical properties of these two compounds, has been described (33,34). 

The same reactants are used for manufacture as for sodium fluoride. An excess of acid is required to crystallize the bifluoride. The crystals are dewatered, dried, sized, and packaged. Cooling of the reaction is necessary to avoid over-heating and decomposition. Reactors and auxiUary equipment are the same as for sodium fluoride. 

Titanium trifluoride is prepared by dissolving titanium metal in hydrofluoric acid (1,2) or by passing anhydrous hydrogen fluoride over titanium trihydrate at 700°C or over heated titanium powder (3). Reaction of titanium trichloride and anhydrous hydrogen fluoride at room temperature yields a cmde product that can be purified by sublimation under high vacuum at 930—950°C. 

Final purification of argon is readily accompHshed by several methods. Purification by passage over heated active metals or by selective adsorption (76) is practiced. More commonly argon is purified by the addition of a small excess of hydrogen, catalytic combustion to water, and finally redistiHation to remove both the excess hydrogen and any traces of nitrogen (see Fig. 5) (see Exhaust control, industrial). With careful control, argon purities exceed 99.999%. 

Indium dichlotide [13465-11 -7/, InCl, made by heating indium in hydrogen chloride or by reduction of InCl iu H2/HCI, forms colorless crystals. Indium monochloride [13465-10-6] InCl, can be formed by passing InCl vapor over heating indium. 

Air and oil filters are made by a dry-web process in which the filter paper is dried over heated metal dmms. The paper is saturated with the phenoHc resin solution, either off- or on-line, and dried in an oven advancing the resin to the B-stage (semicured). The sheet, containing 20—30% resin, is roUed and shipped to the filter-unit manufacturer, where the sheet is convoluted and the filter assembled and cured to the C-stage (fully cured). 

Golorfastness to Atmospheric Contaminants. The test colorfastness to nitrogen oxides, ISO 105-G01 is to assess the fastness of the color to nitrogen oxides that may be present ia hot air that has been passed over heated filaments or from the burning of gas, coal, etc. Specimens are exposed to nitrogen oxides ia a closed container along with standards until the standards have changed to a predetermined extent. 

Potassium trifluoroacetate [2923-16-2] M 152.1, m 140-142°, pK 0.52 (for CFjCOjH). To purify dissolve the salt in trifluoroacetic acid with ca 2% of trifluoroacetic anhydride, filter and evaporate carefully to dryness (avoid over heating), and finally dry in a vacuum at 100°. It can be recrystallised from trifluoroacetic acid (solubility in the acid is ca 50.1%). [J Am Chem Soc 74 4746 1952, 76 4285 1954-, J Inorg Nucl Chem 9 166 1959.]... 

High or low fuel gas pressure ean have a dramatic effect on the operation of a firetube heater. Burners are typically rated as heat output at a specified fuel pressure. A significantly lower pressure means inadequate heat release. Significantly higher pressure causes overfiring and over heating. The most common causes of a fuel gas pressure problem are the failure of a pressure regulator or an unacceptably low supply pressure. 

The reaction is carried out by first reacting the alkyl or aryl halide with magnesium shavings in an ether suspension and then treating with silicon tetrachloride (prepared by passing chlorine over heated silicon). With methyl chloride the following sequence of reactions occur ... 

It is available commercially from several routes including as a product from the manufacture of sodium nitrate from sodium chloride and nitric acid, and from a process involving the passage of ammonia and air over heated platinum and treating the nitric oxide so formed with oxygen. 

Boiling - This involves bringing the water to its boiling point in a container over heat. The water must be maintained at this temperature 15 to 20 minutes. This will disinfect the water. Boiling water is an effective method of treatment because no important waterborne diseases are caused by heat-resisting organisms. 

The modem process for manufacturing nitric acid depends on the catalytic oxidation of NH3 over heated Pt to give NO in preference to other thermodynamically more favour products (p. 423). The reaction was first systematically studied in 1901 by W. Ostwald (Nobel Prize 1909) and by 1908 a commercial plant near Bochum. Germany, was producing 3 tonnes/day. However, significant expansion in production depended on the economical availability of synthetic ammonia by the Haber-Bosch process (p. 421). The reactions occurring, and the enthalpy changes per mole of N atoms at 25 C are ... 

Of the anhydrous dihalides of iron the iodide is easily prepared from the elements but the others are best obtained by passing HX over heated iron. The white (or pale-green) difluoride has the rutile structure the pale-yellow dichloride the CdCl2 structure (based on cep anions, p. 1212) and the yellow-green dibromide and grey diiodide the Cdl2 structure (based on hep anions, p. 1212), in all of which the metal occupies octahedral sites. All these iron dihalides dissolve in water and form crystalline hydrates which may alternatively be obtained by dissolving metallic iron in the aqueous acid. 

Figure 10-171. How air velocity over heated pipe increases heat transfer through forced convection. (Used by permission Chapman, F. S., and Holland, F. A. Chemical Engineering, Dec. 20, 1965, p. 79. McGraw-Hill, Inc. All rights reserved.)...

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