Gravimetric separation

The analysis of low-melting alloys such as Wood s metal is greatly simplified by complexometric titration, and tedious gravimetric separations are avoided. The alloy is treated with concentrated nitric acid, evaporated to a small volume, and after dilution the precipitated tin(IV) oxide is filtered off heavy metals adsorbed by the precipitate are removed by washing with a known volume of standard EDTA solution previously made slightly alkaline with aqueous... 

Gravimetric separation systems. These include jigs, shaking tables, Humphrey-type spiral concentrators, and so on. 

Flotation. In many cases, contaminants adsorbed on the surface of clay particles, or contaminants occurring in soil as discriminate particles, have different surface properties to clean soil particles. By adding special chemical substances, the formation of a hydrophobic surface on the contaminated particles is possible. Pulp aeration results in the attachment of hydrophobic contaminated particles to the surface of the small bubbles that are formed. In this way, selective flotation of these particles is achieved. Contrary to the gravimetric separation methods, flotation offers the possibility to separate contaminated and noncontaminated particles of the same grain size and density but with different surface properties. 

After the first step of the A-methyl-p-toluenesulfonamide production, the sulfonamide containing organic solvent stream is gravimetrically separated from the... 

C10H7NO2 1,2-Naphthoquinone 1-oxime (l-NiUoso-2-naphthol) Complexing agent Extiaction-photometiic Gravimetric Separation Transition and rare eartii metals Co, Fe, Mo, U Co U 3... 

The TRUclean soil washing system is a patented, ex situ modular process that uses soil washing, size fractionation, and gravimetric separation techniques to remediate soils contaminated with radionuclides and heavy metals. The technology developer, Lockheed Martin Corporation, claims... 

Gravimetric separation occurs due to a difference in mass between particles. Densiometric separation is more selective as it classifies materials by density, a property specific to each type of component. Size has no effect on densiometric separation. A number of methods exist to separate materials in these ways. 

Gravimetric separation methods may be complicated or negated if incompatible materials with similar specific gravities are used. 

A hydrocyclone, 44 mm in diameter, is used to separate a suspension of limestone in water. The density of the limestone is 2885 kg/m and the gravimetric separation efficiency was 28.34% while the partition coefficient was determined as 11.62%. Derive a grade efficiency curve to find out the reduced cut size, from the data given in Table 10.2. 

Many precipitation reactions that are useful as separation techniques for gravimetric analysis fail to meet one or both of two requirements for titrimetry ... 

A gravimetric method in which the mass of a particulate analyte is determined following its separation from its matrix. 

A precipitation gravimetric analysis must have several important attributes. Eirst, the precipitate must be of low solubility, high purity, and of known composition if its mass is to accurately reflect the analyte s mass. Second, the precipitate must be in a form that is easy to separate from the reaction mixture. The theoretical and experimental details of precipitation gravimetry are reviewed in this section. 

In some situations the rate at which a precipitate forms can be used to separate an analyte from a potential interferent. For example, due to similarities in their chemistry, a gravimetric analysis for Ca + may be adversely affected by the presence of Mg +. Precipitates of Ca(01T)2, however, form more rapidly than precipitates of Mg(01T)2. If Ca(01T)2 is filtered before Mg(01T)2 begins to precipitate, then a quantitative analysis for Ca + is feasible. 

Gravimetric methods based on precipitation or volatilization reactions require that the analyte, or some other species in the sample, participate in a chemical reaction producing a change in physical state. For example, in direct precipitation gravimetry, a soluble analyte is converted to an insoluble form that precipitates from solution. In some situations, however, the analyte is already present in a form that may be readily separated from its liquid, gas, or solid matrix. When such a separation is possible, the analyte s mass can be directly determined with an appropriate balance. In this section the application of particulate gravimetry is briefly considered. 

When the analyte is already present in a particulate form that is easily separated from its matrix, then a particulate gravimetric analysis may be feasible. Examples include the determination of dissolved solids and the determination of fat in foods. 

Nickel also is deterrnined by a volumetric method employing ethylenediaminetetraacetic acid as a titrant. Inductively coupled plasma (ICP) is preferred to determine very low nickel values (see Trace AND RESIDUE ANALYSIS). The classical gravimetric method employing dimethylglyoxime to precipitate nickel as a red complex is used as a precise analytical technique (122). A colorimetric method employing dimethylglyoxime also is available. The classical method of electro deposition is a commonly employed technique to separate nickel in the presence of other metals, notably copper (qv). It is also used to estabhsh caUbration criteria for the spectrophotometric methods. X-ray diffraction often is used to identify nickel in crystalline form. 

The alkah metals are commonly separated from all other elements except chlorine before gravimetric determination. In the absence of other alkaUes, sodium maybe weighed as the chloride or converted to the sulfate and weighed. WeU-known gravimetric procedures employ precipitation as the uranyl acetate of sodium—2inc or sodium—magnesium. Quantitative determination of sodium without separation is frequently possible by emission or atomic-absorption spectrometric techniques. 

The classical analytical method of deterruination of barium ion is gravimetric, by precipitating and weighing insoluble barium sulfate. Barium chromate, which is more insoluble than strontium chromate in a slightly acidic solution, gives a fairly good separation of the two elements. 

Ultrafiltration utilizes membrane filters with small pore sizes ranging from O.OlS t to in order to collect small particles, to separate small particle sizes, or to obtain particle-free solutions for a variety of applications. Membrane filters are characterized by a smallness and uniformity of pore size difficult to achieve with cellulosic filters. They are further characterized by thinness, strength, flexibility, low absorption and adsorption, and a flat surface texture. These properties are useful for a variety of analytical procedures. In the analytical laboratory, ultrafiltration is especially useful for gravimetric analysis, optical microscopy, and X-ray fluorescence studies. 

Gravimetric analysis The chemical analysis of materials by the separation of the constituents and their measurement by weight. This describes the gas mixture by giving the percentage by weight of each component gas. See also Volumetric analysis. 

At the end of the stirring period cyclandelate s recovered by well-known procedures. For instance, the aqueous organic layers may be separated gravimetrically and the product organic layer washed with an appropriate solvent and then distilled, according to U.S. Patent 3,663,597. 

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