Preliminary treatment

Biuret test. Oxamide, having two CONHj groups, will give this test without any preliminary treatment (c/. urea). Shake o-i g. of oxamide with 1 ml, of 10% NaOH solution, add i drop of very dilute CuSO solution and mix well. A rose-pink coloration is produced. 

The p-phenetidine is usually coloured and the procedure given permits a preliminary treatment with decolourising carbon, thus leading to an almo.st colourless phenacetin directly. 

Traction is typically used to align a bone by a gende, constant pulling action. The pulling force may be transmitted to the bone through skin tapes or a metal pin through a bone. Traction may be used as a preliminary treatment, before other forms of treatment or after cast immobilization. 

Where larger quantities (upwards of Ig) are required, most of the impurities should be removed by preliminary treatments, such as solvent extraction, liquid-liquid partition, or conversion to a derivative (vide supra) which can be purified by crystallisation or fractional distillation before being reconverted to the starting material. The substance is then crystallised or distilled. If the final amounts must be in excess of 25g, preparation of a derivative is sometimes omitted because of the cost involved. In all of the above cases, purification is likely to be more laborious if the impurity is an isomer or a derivative with closely similar physical properties. 

Conventional treatment The preliminary treatment, sedimentation, flotation, trickling filter, rotating biological contactor, activated sludge and chlorination of wastewater. 

Preliminary treatment The removal of metal, rocks, rags, sand, eggshells, and similar materials which may hinder the operation of a treatment plant. Preliminary treatment is accomplished by using equipment such as racks, bar screens, comminutors, and grit removal systems. 

Sulfide ores, after preliminary treatment, most often undergo roasting, that is, heating with air or pure oxygen. With a relatively reactive transition metal such as zinc, the product is the oxide... 

Fluoride ion, and weak acids and bases do not interfere, but nitrate, nitrite, perchlorate, thiocyanate, chromate, chlorate, iodide, and bromide do. Since analysis of almost all boron-containing compounds requires a preliminary treatment which ultimately results in an aqueous boric acid sample, this procedure may be regarded as a gravimetric determination of boron. 

In view of the foregoing remarks, it is clear that all glassware used in the preliminary treatment of samples to be subjected to stripping voltammetry, as well as the apparatus to be used in the actual determination, must be scrupulously cleaned. It is usually recommended that glassware be soaked for some hours in pure nitric acid (6 M), or in a 10 per cent solution of pure 70 per cent perchloric acid, followed by washing with de-ionised water. 

Discussion. Minute amounts of beryllium may be readily determined spectrophotometrically by reaction under alkaline conditions with 4-nitrobenzeneazo-orcinol. The reagent is yellow in a basic medium in the presence of beryllium the colour changes to reddish-brown. The zone of optimum alkalinity is rather critical and narrow buffering with boric acid increases the reproducibility. Aluminium, up to about 240 mg per 25 mL, has little influence provided an excess of 1 mole of sodium hydroxide is added for each mole of aluminium present. Other elements which might interfere are removed by preliminary treatment with sodium hydroxide solution, but the possible co-precipitation of beryllium must be considered. Zinc interferes very slightly but can be removed by precipitation as sulphide. Copper interferes seriously, even in such small amounts as are soluble in sodium hydroxide solution. The interference of small amounts of copper, nickel, iron and calcium can be prevented by complexing with EDTA and triethanolamine. 

Table 4 summarizes the efficiency of membrane filtration as preliminary treatment in the hybrid process to obtain regenerated water for industrial reuse. Working with the adequate cleaning cycle to avoid fouling and to keep a constant flux (10 1 min ) important reduction in suspended solids (90%) and turbidity (60%) of the wastewaters is achieved but there is no significant reduction of other chemical or physical parameters, e.g., conductivity, alkalinity or TDS, or inactivation of E. coli. 

Aqueous standard solutions are a source of certain difficulties In electrothermal atomic absorption spectrometry of trace metals In biological fluids The viscosities and surface tensions of aqueous standard solutions are substantially less than the viscosities and surface tensions of serum, blood and other proteln-contalnlng fluids These factors Introduce volumetric disparities In pipetting of standard solutions and body fluids, and also cause differences In penetration of these liquids Into porous graphite tubes or rods Preliminary treatment of porous graphite with xylene may help to minimize the differences of liquid penetration (53,67) A more satisfactory solution of this problem Is preparation of standards In aqueous solutions of metal-free dextran (50-60 g/llter), as first proposed by Pekarek et al ( ) for the standardization of serum chromium analyses This practice has been used successfully by the present author for standardization of analyses of serum nickel The standard solutions which are prepared In aqueous dextran resemble serum In regard to viscosity and surface tension Introduction of dextran-contalnlng standard solutions Is an Important contribution to electrothermal atomic absorption analysis of trace metals In body fluids. 

Fig. 5.25. Temperature dependence of the starting velocity of change in Au/ZnO film being acted upon by helium metastable atoms after different preliminary treatment [174] (/ - film treated by active hydrogen 2- starting film 3 - film treated by active oxygen)...

Esterification over Amberlyst BD20 was evaluated by processing a model mixture in a fixed-bed reactor. The model reaction mixture was prepared by dissolving 10 wt.% of pure stearic acid (> 97%, Fluka, Germany) in a low-acid vegetable oil (0.04 %) bought in the supermarket. Methanol (> 99.5%) was used without any preliminary treatment. 

It may be necessary to segregate waste streams containing elevated concentrations of arsenic and selenium, especially waste streams with concentrations in excess of lmg/L for these pollutants. Arsenic and selenium form anionic acids in solution (most other metals act as cations) and require special preliminary treatment prior to conventional metals treatment. Lime, a source of calcium ions, is effective in reducing arsenic and selenium concentrations when the initial concentration is below lmg/L. However, preliminary treatment with sodium sulfide at a low pH (i.e., 1-3) may be required for waste streams with concentrations in excess of lmg/L.22 The sulfide reacts with the anionic acids to form insoluble sulfides that are readily separated by means of filtration. 

Pharmacological studies and clinical applications of individual Gelsemium alkaloids or of the total alkaloids have never been reviewed before, so a preliminary treatment is presented in this chapter based on the limited data collected so far. For the convenience of identification, the names, molecular formulas, sources, as well as main references of all the Gelsemium alkaloids reported in the literature to date are listed in Table I. 

Atherton, F. R. et al., J. Chem. Soc., 1945, 382 1948, 1106 It decomposes at 160°C, but prolonged heating at 120°C may have the same effect. Not more than 50 g should be distilled at one time, using high-vacuum conditions (b.p 100-120°C/0.001 mbar) unless a preliminary treatment to remove acidic impurities has been used. 

Dissolution procedures are described for gram samples of graphite or pyrolytic carbon, milligram samples of irradiated fuel particles, and for more readily oxidised forms of carbon, such as charcoal. The first two methods involve heating the samples with mixtures of 70% perchloric and 90% nitric acids (10 1), and must only be used for graphite or pyrolytic carbon. Other forms of carbon must not be oxidised in this way (to avoid explosions), but by a preliminary treatment with nitric acid alone and in portions. 

These data are consistent with the results obtained by Barry (16) who investigated the influence of the preliminary treatment of a specimen of ZnO on the sign of the photoadsorption effect with respect to oxygen. The specimen was first calcined at a high temperature in oxygen and then cooled to room temperature, at which adsorption was subsequently carried out. The untreated specimens showed photodesorption, while on the samples treated by the procedure indicated (saturation with oxygen) there was observed photoadsorption. 

Let us now turn to a comparison of theory with experiment. Comparing (95), (84), and (68), we find that the dependence of the photocatalytic effect K on the position of the Fermi level at the surface s and in the bulk cv of an unexcited sample for the oxidation of water is the same as for the oxidation of CO or for the hydrogen-deuterium exchange reaction. For this reason, such factors as the introduction of impurities into a specimen, the adsorption of gases on the surface of the specimen, and the preliminary treatment of the specimen will exert the same influence on the photocatalytic effect in all the three reactions indicated above. The dependence of K on the intensity I of the exciting light must also be the same in all the three cases. 

The thermally expanded graphite was used without any preliminary treatment the carbon was synthesized by carbonation of the raw material in an argon flow at 500°C with subsequent thermal treatment. Carbon residues strongly differing in the crystallinity degree were obtained as depends on the temperature which ranged from 500°C to 1300°C. The identity of each material was checked by X-ray spectroscopy. 

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