Gas mixtures, preparation

Fill the NMR tube to 1 bar with a gas mixture prepared from the reaction of D2O (95 percent D) with an equimolar mixture of benzoyl chloride and bromide. The reaction... 

This method of analysis was also used by Dubinin for the determination of chloropicrin in the gas mixtures prepared for the testing of activated carbons. 

Kommission Reinhaltung der Luft im VDI und DIN - Normenausschuss KRdL (1981) Measurement of Gases Calibration Gas Mixtures Preparation by Continuous Injection Method, Directive 13.040.01., www.vdi.de (accessed 14 May 2014). 

The solution of the work compression part of the compressor selection problem is quite accurate and easy when a pressure-enthalpy or Mollier diagram of the gas is available (see Figures 12-24A-H). These charts present the actual relationship of the gas properties under all conditions of the diagram and recognize the deviation from the ideal gas laws. In the range in which compressibility of the gas becomes significant, the use of the charts is most helpful and convenient. Because this information is not available for many gas mixtures, it is limited to those rather common or perhaps extremely important gases (or mixtures) where this information has been prepared in chart form. The procedure is as follows ... 

In static runs gas is supplied to the ion source only at a rate sufficient to compensate the outflow through the leak (0.5 cc./sec. for air, equal to conductance of leak). The gas mixtures were prepared in two 2-liter storage flasks of the gas handling system. Flow runs can be made by passing gas through the ion source. Different flow rates were obtained by interposing capillary tubes in series with the flow system. Flow rates with an average linear velocity of up to 10 meters sec.-1 could be obtained. Since the distance from the foil window to the leak is about 3 cm., the contact time for irradiation at this velocity is some 3 msec. 

The chlorination of methyl chloroformate in sunlight was first reported by Hentschel, but without a detailed description of either the procedure or the results. The first step of the present procedure for the preparation of trichloromethyl chloroformate utilizes an ultraviolet light source and affords a simple and reproducible way to obtain this reagent. Although trichloromethyl chloroformate may also be synthesized by photochemical chlorination of methyl formate,the volatility of methyl formate causes losses during the reaction and increases the hazard of forming an explosive mixture of its vapor and chlorine gas. The preparation of trichloromethyl chloroformate by chlorination of methyl chloroformate in the dark with diacetyl peroxide as initiator has been reported. However, the procedure consists of several steps, and the overall yield is rather low. 

Apart from the reactions described above for the formation of thin films of metals and compounds by the use of a solid source of the material, a very important industrial application of vapour phase transport involves the preparation of gas mixtures at room temperature which are then submitted to thermal decomposition in a high temperature furnace to produce a thin film at this temperature. Many of the molecular species and reactions which were considered earlier are used in this procedure, and so the conclusions which were drawn regarding choice and optimal performance apply again. For example, instead of using a solid source to prepare refractory compounds, as in the case of silicon carbide discussed above, a similar reaction has been used to prepare titanium boride coatings on silicon carbide and hafnium diboride coatings on carbon by means of a gaseous input to the deposition furnace (Choy and Derby, 1993) (Shinavski and Diefendorf, 1993). 

Such an electrochemical arrangement can also be used to transport oxygen from one electrode to the other by the imposition of an externally applied potential. This technique, known as coulometric titration , has been used to prepare flowing gas mixtures of oxygen/argon with a controlled oxygen partial pressure, to vary the non-stoichiometry of oxides, to study the thermodynamics of dilute oxygen solutions in metals, and to measure the kinetics of metal oxidation, as examples. 

Three flow systems with different gas composition were prepared so that the transient response experiments could be completed for three different gas mixtures within a few minutes. A more detailed description of transient response method used in this study can be found elsewhere (.6, 7, 8). ... 

Mixtures of 25-30% fluorine diluted with nitrogen were used in this work. The gas mixtures were prepared in a secondary container. The appropriate polyether was dissolved either in perfluoro-2-butyl-THF (FC-75) or in Krytox GPL 100 (a fluorinated oil), which also contained about 5 g of pulverized NaF to absorb the relased HE The reaction mixture was cooled to - 10°C, stirred with the aid of a vibromixer and irradiated with a 450-W medium-pressure mercury lamp. A stream of fluorine in nitrogen (ca. 140 ml/min) was passed into the mixture such that the temperature did not rise above +10°C. The reaction was stopped after 200 mmol of fluorine had been passed through. The mixture was poured into water and the organic layer was washed with sodium bicarbonate solution. The water layer was extracted twice with CFCL. The combined fluorocarbon fractions were washed with water, dried with MgS04, and filtered, and the solvent was removed under reduced pressure. 

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