Evolved gas

From equation (2.8), the gaseous reaction products are seen to be 3CO2, 3CO and 2N2. Therefore, the reaction produces 8 moles of product gases from 4 moles of KNO3 (404 g) plus 7 moles of charcoal (84 g) plus 1 mole of sulfur (32 g) which is equivalent to a total of 520 g of black powder. 

To calculate the number of moles of gas produced per gram of black powder burned, 

If the actual temperature of the product gases is 2000 °C, the calculated volume at this temperature and one atmosphere pressure would be considerably greater, as shown by equation (2.16). 

From equation (2.8), the gaseous reaction products are seen to be 3CO2, 3CO and 2N2. Therefore, the reaction produces 8 moles of product gases 

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Ra.don Sepa.ra.tion, Owing to its short half-life, radon is normally prepared close to the point of use in laboratory-scale apparatus. Radium salts are dissolved in water and the evolved gases periodically collected. The gas that contains radon, hydrogen, and oxygen is cooled to condense the radon, and the gaseous hydrogen and oxygen are pumped away. 

The classical synthesis iavolves the dissolution of a 33% Sb—67% Zn alloy by hydrochloric acid the evolved gases contain up to 14% stibiae. A detailed procedure usiag a Sb—Mg alloy has also beea described (16). Aluminum hydride or alkaU metal borohydrides have been used to reduce antimony(III) ia acidic aqueous solutioa to produce stibiae. A 23.6% yield of stibiae, based oa the borohydride used, has beea reported (17). A 78% yield based oa Sb has beea obtaiaed by gradually adding a solutioa that is 0.4 Min SbCl and saturated ia NaQ, to aqueous NaBH at mol ratios of NaBH iSbQ. >10 (18). 

A convenient method for assessing the extent of surface oxidation is the measurement of volatile content. This standard method measures the weight loss of the evolved gases on heating up to 950°C in an inert atmosphere. The composition of these gases consists of three principal components hydrogen, carbon monoxide, and carbon dioxide. The volatile content of normal furnace blacks is under 1.5%, and the volatile content of oxidized special grades is 2.0 to 9.5%. 

B. a-Hydroxyphenazine (demethylalion). A solution of 4.2 g. (0.02 mole) of a-methoxyphenazine, from A above, in 125 ml. of 55% hydrobromic acid (Note 7) is placed in a 250-ml. round-bottomed flask fitted with a reflux condenser. The flask is immersed in an oil bath, and the solution is heated to 110-120° for 5 hours the evolved gases are absorbed with water in a trap. The reaction mixture is cooled to room temperature, diluted with about 125 ml. of water, almost neutralized with sodium hydro.xide (Note 8), and extracted six times with 30- to 40-ml. portions of ether. The combined ether extracts arc extracted with 25-ml. portions of 10% sodium hydroxide solution (Note 9) until no more purple sodium salt is remox ed from the ether. The aqueous extracts are combined, made acid to litmus with dilute acetic acid, and re-extracted four times with 50-ml. portions of ether. The combined ether extracts are dried over anhydrous sodium sulfate, and the ether is removed by distillation on a steam bath. The residue is recrystallized as follows It is dissolved in the least possible amount of hot alcohol, water... 

Crucible geometry. The geometry of the crucible can alter the slope of the thermogravimetric curve. Generally, a flat, plate-shaped crucible is preferred to a high-form cone shape because the diffusion of any evolved gases is easier with the former type. 

Ref 9 contains a method for detg the chemical stability of expls and propints at 120° by collecting evolved gases in a burette and then analyzing them by titration or by detg the acidity of a w soln... 

Thermal desorption of solid traps by microwave energy is unsuitable for thermally labile compounds. In microwave thermal analysis [431] the (solid) sample is heated directly via interactions of the microwaves with the sample, providing more even heating and reduction of temperature gradients in comparison to heating with electrical furnaces. By passing air over a microwave-heated volatile sample evolved gases may be collected [432]. 

Both chemical and physical properties of the reaction medium will dictate the required level of cavitation power. High viscosity media with low vapor pressure will require higher energy to generate cavitation. The presence of entrained or evolved gases will facilitate cavitation, as will the presence or generation of solid particles. 

Oxidation of the durene derivative to benzenehexacarboxylic acid (mellitic acid) in an autoclave is normally effected in stages, initially by heating at 80-104°C with the vent open to allow escape of the evolved gases. Subsequent heating to a higher temperature with the vent closed completes the reaction. On one occasion omission of the first vented heating phase led to explosive rupture of the autoclave at 80° C. 

Figure 18 (a) GC-FTIR Gram-Schmidt chromatograms from evolved gases from PHB at... 

Table I. Evolved Gases From 2 MeV He+ Irradiation of 0.9 nm Palladium Acetate Film. Molecules arranged in order of decreasing abundance within each group...

In moulds for complex product shapes it can be advantageous to provide vacuum extraction to the cavities so that air and evolved gases can be removed from the mould cavity, before and during vulcanisation to ensure complete cavity fdling, and a product without air (gas) blemishes. 

In this technique, both the amount and composition of the volatile component are measured as a function of temperature. The composition of the evolved gases can be determined using gas chromatography, mass spectrometry, or infrared spectroscopy. 

Note All the above should be checked by analysing the evolved gases and residual solids. Above 400°C further decomposition occurs with loss of S02 and S03 to give copper oxide. 

Evolved gases were monitored continuously for 02, C02, NOx, CO, and total hydrocarbons (THC) by a continuous emission monitoring system (CEMS). Batch samples of the offgases were also taken and analyzed for NH3, HCN, residual energetic materials, volatile organic compounds, and N2. The batch samples were collected over the entire duration of each run, and the single value reported represents the average concentration for the whole run. 

As a partial compromise between the use of on-site instrumental analysis and laboratory analysis, a passive sampler can be immersed into the soil (at a specified depth or at several depths) to collect the evolved gases that are adsorbed onto a solid-phase support. The sampler is then removed to the laboratory, where the gases are transferred by Curie point desorption, directly into the ion source of an interfaced quadrupole mass spectrometer. This procedure has its origin in the petroleum exploration industry, and the samplers can be used at a considerable range of depths (Einhom et al., 1992). 

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