Chemically pure

Substance chemically pure. This is almost invariably the cause of a sharp melting-point. 

U02(C02) 3. The pregnant solution is concentrated and purified by ion exchange or solvent extraction, yielding a stripping solution of ca 50 kg/m U Og. Uranium is then precipitated chemically. Pure U Og is obtained by calcination (see Uraniumand URANIUM COMPOUNDS). 

United States Pharmacopeia stronger ammonia water ammonia test solution normal (1 N) aqua ammonia chemically pure technical, Bh°... 

Vanadium Carbide. Vanadium pentoxide [1314-62-17, V2O5, or vanadium trioxide [1314-34-7] VO3, are the most satisfactory oxides for the preparation of VC. Vanadium pentoxide is best prepared by igniting chemically pure ammonium vanadate [7803-55-6] NH VO, in the presence of moist oxygen to avoid reaction with nitrogen V2O3 is obtained by reduction of V2O3 with hydrogen (see Vanadium compounds). 

Chemically pure calcium carbide [75-20-7] is a colorless solid however, the pure material can be prepared only by very special techniques. 

These are known as chemically pure (CP) cadmiums. With the development of other uses for cadmium and selenium, costs have risen substantially in recent years. Some cost reduction may be obtained by use of the cadmium Hthopones. These have the same relative shades but have been coprecipitated onto about 60% barium sulfate. The resulting extensions give better money value, if the higher pigment loading can be tolerated, with no loss in properties. 

Water supplies should never be assumed to be chemically pure. Groundwater from wells and springs contains dissolved impurities. Its properties depend... 

Flow markers are often chosen to be chemically pure small molecules that can fully permeate the GPC packing and elute as a sharp peak at the total permeation volume (Vp) of the column. Examples of a few common flow markers reported in the literature for nonaqueous GPC include xylene, dioctyl phthalate, ethylbenzene, and sulfur. The flow marker must in no way perturb the chromatography of the analyte, either by coeluting with the analyte peak of interest or by influencing the retention of the analyte. In all cases it is essential that the flow marker experience no adsorption on the stationary phase of the column. The variability that occurs in a flow marker when it experiences differences in how it adsorbs to a column is more than sufficient to obscure the flow rate deviations that one is trying to monitor and correct for. 

Q Preparation of 2-Acetyi-3-Methyi-5-(2-Oxo-2,5-Dihydro-4-Furyi)Benzo[b]Furan (3556 CB) (1) A suspension of 2 grams of the compound prepared according to (B) in 20 ml of concentrated hydrochloric acid, is heated to about 50°C, just until it dissolves. Thereafter it is heated for 2 minutes to 70°C, just until precipitation commences. The mixture is allowed to cool, diluted with water, filtered, the residue washed, dried, and sublimed at 200°C and 0.1 mm pressure, 1.4 grams of product (Yield 70%) Is obtained, MPc = 218°-221°C. A second sublimation produces a chemically pure product, MP = 221°-222°C. 

It was assumed throughout that the compound which separated out from the solution was chemically pure, but this is not always the case. The purity of the precipitate depends inter alia upon the substances present in solution both before and after the addition of the reagent, and also upon the exact experimental conditions of precipitation. In order to understand the influence of these and other factors, it will be necessary to give a short account of the properties of colloids. 

The electric voltage also has an influence on the film thickness in TFL. Shen et al. [50] used hexadecane with the addition of cholesteryl LCs in chemically pure as the lubricant to check the variation of its film thickness by applying an external DC voltage. With the technique of ROII [3,4,51], the effects of LCs polarity and concentration on film thickness and the effects of lubricant molecules on a film-forming mechanism were investigated by them. 

Chemically pure semiconducor materials can absorb only those photons, the energy hv of which exceeds the band gap E . Therefore, E. value determines the "red boundary of the light that is used in photocatalytic action of these materials. By way of example. Table 1 presents the values of Eg and the corresponding values of boundary wave length Xg= hc/E (where c is the velocity of light) for some semiconductor and dielectric oxides [2]. However, a semiconductor PC can be sensitized to light with X> by chemical modifications of its surface layer or adsorption of certain molecules on its surface, provided that such treatment creates additional full or empty electron levels in the band gap of the semiconductor material. 

Osterherg, T. Svensson, M. Lundahl, P, Chromatographic retention of drug molecules on immohilized liposomes prepared from egg phospholipids and from chemically pure phospholipids, Eur. J. Pharm. Sci. 12, 427 139 (2001). 

As already mentioned, macular zeaxanthin comprises two stereoisomers, the normal dietary (3/(,37()-/caxanthin and (3f ,3 S)-zeaxanthin(=(meyo)-zeaxanthin), of which the latter is not normally a dietary component (Bone et al. 1993) and is not found in any other compartment of the body except in the retina. The concentration of (tneso)-zeaxanthin in the retina decreases from a maximum within the central fovea to a minimum in the peripheral retina, similar to the situation with (3/ ,37 )-zeaxanthin. This distribution inversely reflects the relative concentration of lutein in the retina and gave rise to a hypothesis (Bone et al. 1997) that (meso)-zeaxanthin is formed in the retina from lutein. This was confirmed by an experiment in which xanthophyll-depleted monkeys had been supplemented with chemically pure lutein or (3/ ,37 )-zeaxanthin (Johnson et al. 2005). (Meyo)-Zeaxanthin was exclusively detected in the retina of lutein-fed monkeys but not in retinas of zeaxanthin-fed animals, demonstrating that it is a retina-specific metabolite of lutein only. The mechanism of its formation has not been established but may involve oxidation-reduction reactions that are mediated photochemically, enzymatically, or both. Thus, (meso)-zeaxanthin is a metabolite unique to the primate macula. 

An alternative to the extraction of intact PHA polymer is the isolation of PHA monomers, oligomers, or various derivatives such as esters [74]. PH As are composed of stereo-chemically pure P-3-hydroxyacids, and therefore can be used as a source of optically pure organic substrates for the chemical and pharmaceutical industry [79]. In this protocol, the defatted cake containing PHA polymer would be chemically treated to obtain the PHA derivatives. For example, transesterification of the meal with methanol would give rise to methyl esters of 3-hydroxyalkanoic acids. The PHA derivatives would then be separated from the meal with appropriate solvents. One potential disadvantage of this method is the potential alteration of the quality of the residual meal if the harsh chemical treatments required for the production of PHA derivatives lead to protein or amino acid breakdown. 

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