Columns decomposition

The arsenic in each fraction was determined by reduction to the corresponding arsine in the zinc reductor column, decomposition of the... 

This is the case, e.g., with TMS derivatives of Krebs cycle acids, containing keto groups. These derivatives do not provide a simple peak, probably owing to on-column decomposition and, therefore, if keto acids are present in the sample conversion into an oxime [159] is recommended. A 10-mg amount of acids and 10 mg of hydroxylammo-nium chloride are placed in a 5-ml test-tube fitted with a ground-glass stopper and are dissolved in 1 ml of dry pyridine. After standing for 10 min at room temperature 0.1 ml of TMCS and 0.1 ml of HMDS are added. The reaction is completed within a few minutes... 

Although bottom-water masses are relatively old in the NEPAP, bottom-water oxygen concentrations remain well above 2mil-1 and hence they probably do not influence benthic community structure (Levin Gage, 1998). In the eastern tropical Pacific, oxygen-minimum zones appear in mid-water (100-1000m) due to intense water column decomposition but they do not extend to abyssal depths (Wishner etal., 1990). 

If the sample to be analyzed is nonvolatile, the techniques of derivatization or pyrolysis GC can be utilized. This latter technique is a modification wherein a nonvolatile sample is pyrolyzed before it enters the column. Decomposition products are separated in the gas chromatographic column, after which they are qualitatively and quantitatively determined. Analytical results are obtained... 

This, in general, has been our methodological approach in the study of the metabolism of the above mentioned classes of compounds. As we reported, the procedures used were similar in all our studies that were performed by chromatographic and spectrometric techniques. Particular attention was paid to the gas chromatographic behaviour of some of these drugs and their metabolites, in relation to column decomposition and, hence, misidentification, Carbamazepine, for instance, degrades... 

If decomposition in the reboilers contaminates the product, then this dictates that no finished products be taken from the bottoms of columns. 

Hydrogen chloride released dissolves in water during condensation in the crude oil distillation column overhead or in the condenser, which cause corrosion of materials at these locations. The action of hydrochloric acid is favored and accelerated by the presence of hydrogen sulfide which results in the decomposition of sulfur-containing hydrocarbons this forces the refiner to inject a basic material like ammonia at the point where water condenses in the atmospheric distillation column. 

Place in the flask 2 g. of benzophenone, 15 ml. of isopropanol and 2 5 g. of aluminium isopropoxide. This mixture has now to be heated gently under reflux so that the temperature registered by the thermometer in the column does not exceed 80°, i.e., so that only acetone distils. For this purpose, the flask should preferably be heated in an oil-bath direct heating, even over an asbestos sheet, may cause local overheating and decomposition the use of a water-bath on the other hand may make the column undesirably damp. 

Fig. 3. Schematic of toluene diamine phosgenation process A, cold phosgenator B, hot phosgenator C, wash column D, solvent distillation E, preflasher F, evaporator G, TDI distillation H, phosgene removal I, HCl absorber and K, phosgene decomposition.

Manufacture. Aqueous sodium hydroxide, sodium bicarbonate, sodium carbonate, or sodium sulfite solution are treated with sulfur dioxide to produce sodium metabisulfite solution. In one operation, the mother Hquor from the previous batch is reinforced with additional sodium carbonate, which need not be totally in solution, and then is treated with sulfur dioxide (341,342). In some plants, the reaction is conducted in a series of two or more stainless steel vessels or columns in which the sulfur dioxide is passed countercurrent to the alkaH. The solution is cooled and the sodium metabisulfite is removed by centrifuging or filtration. Rapid drying, eg, in a stream-heated shelf dryer or a flash dryer, avoids excessive decomposition or oxidation to which moist sodium metabisulfite is susceptible. 

The first step in CTO distillation is depitching. A relatively small distillation column is used as a pitch stripper. The vapor from the pitch stripper is fed directiy into the rosin column, where rosin and fatty acids are separated. Rosin is taken from the bottoms of the column and fatty acids as a sidestream near the top. Palmitic acid and light neutrals are removed in the rosin column as heads. The operation is designed to minimize holdup and product decomposition. Care is taken to prevent carryover of some of the heavier neutrals, such as the sterols, from the depitcher to the rosin column (24). 

Dilute (1—3%), chloride-containing solutions of either HOCl, hypochlorite, or aqueous base, can be stripped in a column against a current of CI2, steam, and air at 95—100°C and the vapors condensed giving virtually chloride-free HOCl solutions of higher concentration in yields as high as 90% (122—124). Distillation of more concentrated solutions requires reduced pressure, lower temperature, and shorter residence times to offset the increased decomposition rates. 

Temperature-sensitive mixtures are to be separated. To avoid decomposition and/or polymerization, vacuum operation may then be necessary. The smaller liqmd holdup and pressure drop theoretical stage of a packed column may be particularly desirable. 

When considering the availability of nutrients, it is also necessary to examine the significance of nutrient re-use within the waterbody. These internal sources amount not to an additional load, but a multiplier on the recyclability of the same load. This nutrient recycling and the internal stores from which they are recycled are often misunderstood, but there is a dearth of good published data about how these recycling mechanisms operate. Microbial decomposition in the water column is one of several internal loops recognized in recent years, but these are not closed and the flux of nutrients recycled through them is delayed rather than retained. 

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