Dissolution/dilution methods

Sucralfate. Sucralfate [54182-58-0] (Carafate) (6) is a white amorphous powder soluble in dilute hydrochloric acid and sodium hydroxide. It is practically insoluble in water, ethanol, and carbon tetrachloride. Dissolution of aluminum occurs at pH <3. It may be prepared by the method described in Reference 7. 

The analytical chemistry of titanium has been reviewed (179—181). Titanium ores can be dissolved by fusion with potassium pyrosulfate, followed by dissolution of the cooled melt in dilute sulfuric acid. For some ores, even if all of the titanium is dissolved, a small amount of residue may still remain. If a hiU analysis is required, the residue may be treated by moistening with sulfuric and hydrofluoric acids and evaporating, to remove siUca, and then fused in a sodium carbonate—borate mixture. Alternatively, fusion in sodium carbonate—borate mixture can be used for ores and a boiling mixture of concentrated sulfuric acid and ammonium sulfate for titanium dioxide pigments. For trace-element deterrninations, the preferred method is dissolution in a mixture of hydrofluoric and hydrochloric acids. 

At present time the use of oxide single erystals sueh as bismuth germanate (Bi Ge O, ) and pai atellurite (TeO,) as deteetors in opto-eleetronies stimulate produetion of high purity Bi, Te, Ge and their oxides Bi O, GeO, TeO,. This requires development of analytieal teehniques for purity eontrol of these materials. For survey traee analysis atomie emission speetrometry (AES) and mass speetrometry (MS) with induetively eoupled plasma (ICP) is widely used. However, the deteetion limits of impurities aehievable by these methods for the analysis of high purity solids are limited by neeessity of sample dissolution in pure aeids and dilution up to 5 10 times for ICP-MS and 50-100 for ICP-AES. One of the most effeetive ways to improve the analytieal performanees of these methods is pre-eoneentration of miero-elements. 

An initial solution was prepared by dissolving metallic niobium powder in 40% hydrofluoric acid. The dissolution was performed at elevated temperature with the addition of a small amount of nitric acid, HN03, to accelerate the process. The completeness of niobium oxidation was verified by UV absorption spectroscopy [21]. The prepared solution was evaporated to obtain a small amount of precipitate, which was separated from the solution by filtration. A saturated solution, containing Nb - 7.01 mol/1, HF - 42.63 mol/1, and corresponding to a molar ratio F Nb = 6.08, was prepared by the above method. The density of the solution at ambient temperature was p = 2.0 g/cc. Concentrations needed for the measurements were obtained by diluting the saturated solution with water or hydrofluoric acid. 

The electrolyte salt must be processed to recover the ionic plutonium orginally added to the cell. This can be done by aqueous chemistry, typically by dissolution in a dilute sodium hydroxide solution with recovery of the contained plutonium as Pu(OH)3, or by pyrochemical techniques. The usual pyrochemical method is to contact the molten electrolyte salt with molten calcium, thereby reducing any PUCI3 to plutonium metal which is immiscible in the salt phase. The extraction crucible is maintained above the melting point of the contained salts to permit any fine droplets of plutonium in the salt to coalesce with the pool of metal formed beneath the salt phase. If the original ER electrolyte salt was eutectic NaCl-KCl a third "black salt" phase will be formed between the stripped electrolyte salt and the solidified metal button. This dark-blue phase can contain 10 wt. % of the plutonium originally present in the electrolyte salt plutonium in this phase can be recovered by an additional calcium extraction stepO ). 

Isolation may occur by liquid-solid interaction (extraction, dissolution) or heat (thermal, pyrolytic, laser). Extraction methods easily handle qualitative screening for low- to medium-MW compounds fail for high-MW components or polymer-bound functionalities and are less reliable quantitatively (analyte dependent). When applicable, dissolution methods suffer from sensitivity, because of the dilution effect on account of the polymer. In-polymer analysis performs well for qualitative screening, but is as yet not strongly performing for quantitative analysis, except for some specific questions. 

Blood Wet ashing with acid mixtures residue dissolution in dilute HCI04 ASV with mercury-graphite electrode (NIOSH method P CAM 195) 40 pg/L 95-105 NIOSH 1977d... 

Blood Wet ashing with HN03 residue dissolution in dilute HN03 GFAAS (NIOSH method P CAM 214) 100 pg/L No data NIOSH 1977g... 

Urine Extraction of sample with polydithio-carbamate resin and NaOH filtration on cellulose ester membrane neutralization with NaOH ashing dissolution and heating dilution with distilled water ICP/AES (Method P CAM 8310) 0.005 pg/mL 100 NIOSH 1984... 

These dyes have affinity for one or, usually, more types of hydrophobic fibre and they are normally applied by exhaustion from fine aqueous dispersion. Although pure disperse dyes have extremely low solubility in cold water, such dyes nevertheless do dissolve to a limited extent in aqueous surfactant solutions at typical dyeing temperatures. The fibre is believed to sorb dye from this dilute aqueous solution phase, which is continuously replenished by rapid dissolution of particles from suspension. Alternatively, hydrophobic fibres can absorb disperse dyes from the vapour phase. This mechanism is the basis of many continuous dyeing and printing methods of application of these dyes. The requirements and limitations of disperse dyes on cellulose acetate, triacetate, polyester, nylon and other synthetic fibres will be discussed more fully in Chapter 3. Similar products have been employed in the surface coloration of certain thermoplastics, including cellulose acetate, poly(methyl methacrylate) and polystyrene. 

Furfural even in dilute aqueous solution gives, almost at once, a precipitate of the phenylhydrazone with phenylhydrazine acetate. Collect the precipitate at the pump and dry. Purify by dissolution in a little ether and careful addition of petrol ether until crystallisation begins. Melting point 97°-98°. Method for quantitative determination of furfural. 

Flow patterns of hydrodynamic systems like the compendial dissolution apparatus may be qualitatively characterized by means of dilute dye injection (e.g., methylene blue) or by techniques using particulate materials such as aluminum powders or polystyrene particles. Flow patterns may be also visualized by taking advantage of density or pH differences within the fluid stream. The Schlieren method, for instance, is based on refraction index measurement. Hot wire anemo-metry is an appropriate method to quantitatively characterize flow rates. The flow rate is proportional to the cooling rate of a thin hot wire presented to the stream. Using laser Doppler... 

Elemental composition Mg 60.32%, O 39.68%. The oxide can be identified nondestructively by x-ray methods. Oxygen content may be determined by elemental microanalysis. Magnesium may be analyzed by AA or ICP following dissolution of the oxide in nitric acid and appropriate dilution with water. 

Dissolution was carried out with the paddle method according to USP XXI, using a Prolabo dissolution tester. The dissolution medium was 1000 ml of distilled water at 37 0.5°C and 50 rev min-1. At appropriate time intervals, 5 ml of sample was withdrawn and an equal volume of medium was added to maintain a constant volume. Sample were filtered, diluted with lithium carbonate solution as an internal standard, and analysed using a Dr Lange MD 70 flame photometer. Each dissolution profile is the average of six separate tablets. 

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