Operations dissolving

Xylene cyanole-methyl orange indicator, Schoepfie modification (for partially color blind operators) dissolve 0.75 g xylene cyanole FT (Eastman No. T 1579) and 1.50 g methyl orange in 1 liter of water. 

When all the violet dye is off the column, begin to collect and evaporate 10-ml. fractions. Two or three fractions, which on evaporation yield little or no residue, will precede the appearance of the 7-benzene hexachloride. Continue to collect 10-ml. fractions and evaporate until no more 7-benzene hexachloride is obtained. Stop the column operation, dissolve the several 7-benzene hexachloride residues with a minimum quantity of n-hexane, and pour into a tared 125-ml. Erlenmeyer flask. Evaporate under vacuum, using the solvent evaporator, at 60° and finally at room temperature for 5 minutes with a high vacuum pump. Release the vacuum, wipe the flask with a clean, moist towel, and weigh after allowing the flask to come to equilibrium near the balance. Calculate the percentage of 7-benzene hexachloride in the original sample. 

In transgenic hairy root cultures, the concentration of IgG antibody in the biomass increased by 52% relative to the levels obtained under air when the roots were cultured at a dissolved oxygen tension of 150% air saturation [17]. Compared with root cultures grown at 50% air saturation, which is a realistic operating dissolved oxygen tension in poorly mixed, large-scale root reactors, oxygen enrichment to 150% air saturation improved total antibody accumulation 2.9-fold. 

It is recognized that filtration is operational, that colloidal-bound PCB congeners are not retained by the filter, and that operational dissolved measurements may be biased positively by colloidal material. Techniques to measure truly dissolved PCBs include gas sparging, differential diffusion into membrane-bound lipids (e.g., semipermeable membrane devices, [230]), and selective adsorption (e.g. non-equilibrium solid phase microextraction [231, 232]). Unfortunately, none of these techniques has sufficient sensitivity to reliably and unambiguously measure truly dissolved PCB congeners at the levels present in the Great Lakes. 

Like other chemicals, organochlorines occur in seawater in a continuum of dissolved, colloidal and discrete particulate forms Gustafsson and Gschwend, 1997). Operationally, dissolved and particulate suspended forms may be distinguished on the basis of separation techniques such as filtration or centrifugation. Ihe separation may depend on size and density of the particles it may also depend on the composition of the suspension. For instance, particles smaller than the nominal filter pore size are retained on a clogged filter. 

H2S is found with the reservoir gas and dissolved in the crude (< 50 ppm by weight), but it is formed during refining operations such as catalytic cracking, hydrodesulfurization, and thermal cracking or by thermal decomposition of sulfur[Pg.322]

These water streams contain mainly dissolved salts ammonium chloride and sulfide, sodium chloride, traces of cyanide, phenols for water coming from catalytic and thermal cracking operations. 

The material of interest is dissolved in a volatile solvent, spread on the surface and allowed to evaporate. As the sweep moves across, compressing the surface, the pressure is measured providing t versus the area per molecule, a. Care must be taken to ensure complete evaporation [1] and the film structure may depend on the nature of the spreading solvent [78]. When the trough area is used to calculate a, one must account for the area due to the meniscus [79]. Barnes and Sharp [80] have introduced a remotely operated barrier drive mechanism for cleaning the water surface while maintaining a closed environment. 

Lithium aluminium hydride if carelessly manipulated may be dangerous for two distinct reasons. The material is caustic, and should not be allowed to touch the skin it is particularly important that the finely divided material should be kept away from the lips, nostrils and eyes, and consequently pulverisation in a mortar must be carried out with the mortar in a fume-cupboard, and with the window drawn down as far as possible in front of the operator. This danger from handling has however been greatly reduced, for the hydride is now sold in stated amounts as a coarse powder enclosed in a polythene bag in a metal container this powder dissolves readily in ether, and preliminary pulverisation is unnecessary. 

The flask A is heated in a suitable bath until all the solid has dissolved a stream of inert gas may be passed through the apparatus during this operation. The flask is allowed to cool in order that the compound may crystallise out. 

A special apparatus (Fig. Ill, 40,1) renders the preparation of iodides from alcohols a very simple operation. The special features of the apparatus are —(i) a wide bored (3-4 mm.) stopcock A which considerably reduces the danger of crystallisation in the bore of the tap of the iodine from the hot alcoholic solution (ii) a reservoir B for the solid iodine and possessing a capacity sufficiently large to hold all the alkyl iodide produced (iii) a wide tube C which permits the alcohol vapour fix)m the flask D to pass rapidly into the reservoir B, thus ensuring that the iodine is dissolved by alcohol which is almost at the boiling point. An improved apparatus is shown in Fig. Ill, 40, 2, a and b here a... 

The distillate was dissolved in a mixture of 350 ml of dry diethyl ether and 45 g of dry triethylamine (dried over powdered KQH). Trimethylchlorosilane (45 g) was added in 20 min with cooling at about 10°C. After standing for 1 h at room temperature the precipitate was sucked off on a dry sintered-glass funnel and rinsed with pentane. The filtrate was concentrated in a water-pump vacuum- The small amount of salt which precipitated during this operation was removed by a second suction filtration. Subsequent distillation afforded the trimethyl silyl ether, b.p. 100°C/15 mmHg, 1.4330, in 944 yield. 

Potentiometric electrodes also can be designed to respond to molecules by incorporating a reaction producing an ion whose concentration can be determined using a traditional ion-selective electrode. Gas-sensing electrodes, for example, include a gas-permeable membrane that isolates the ion-selective electrode from the solution containing the analyte. Diffusion of a dissolved gas across the membrane alters the composition of the inner solution in a manner that can be followed with an ion-selective electrode. Enzyme electrodes operate in the same way. 

Suitable inlets commonly used for liquids or solutions can be separated into three major classes, two of which are discussed in Parts A and C (Chapters 15 and 17). The most common method of introducing the solutions uses the nebulizer/desolvation inlet discussed here. For greater detail on types and operation of nebulizers, refer to Chapter 19. Note that, for all samples that have been previously dissolved in a liquid (dissolution of sample in acid, alkali, or solvent), it is important that high-purity liquids be used if cross-contamination of sample is to be avoided. Once the liquid has been vaporized prior to introduction of residual sample into the plasma flame, any nonvolatile impurities in the liquid will have been mixed with the sample itself, and these impurities will appear in the results of analysis. The problem can be partially circumvented by use of blanks, viz., the separate examination of levels of residues left by solvents in the absence of any sample. 

The solution or matrix consists of the substance under investigation (the solute) dissolved in a high-boiling-point solvent that evaporates only slowly in the vacuum of the mass spectrometer at an operating temperature of about 20 to 30°C. 

In addition to existing as helices in crystals, there is evidence that certain vinyl polymers also show some degree of regular alternation between trans and gauche conformations in solution. In solution, the chain is free from the sort of environmental constraints that operate in a crystal, so the length of the helical sequence in a dissolved isotactic vinyl polymer may be relatively short. 

Absorption, or gas absorption, is a unit operation used in the chemical industry to separate gases by washing or scmbbing a gas mixture with a suitable hquid. One or more of the constituents of the gas mixture dissolves or is absorbed in the Hquid and can thus be removed from the mixture. In some systems, this gaseous constituent forms a physical solution with the Hquid or the solvent, and in other cases, it reacts with the Hquid chemically. 

The wastewater produced in this process consists mostly of water used in cleanup and propellant conveyance and sorting operations. Techniques such as the use of activated carbon and biological treatment are being investigated for the removal of solvents and dissolved organic compounds (143). 

Israel Mining Industries developed a process in which hydrochloric acid, instead of sulfuric acid, was used as the acidulant (37). The acidulate contained dissolved calcium chloride which then was separated from the phosphoric acid by use of solvent extraction using a recyclable organic solvent. The process was operated commercially for a limited time, but the generation of HCl fumes was destmctive to production equipment. 

At the end of xanthation, any remaining traces of CS2 are flushed from the wet churn prior to, or in some cases by, admitting a charge of the dissolving or mixer soda in order to commence dissolution. For a dry churn operation, the vessel is opened to allow the golden xanthate cmmbs to be discharged into a separate mixer. 

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