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Gravimetric calculations mixtures

Precipitation reactions have many applications. One is to make compounds. The strategy is to choose starting solutions that form a precipitate of the desired insoluble compound when they are mixed. Then we can separate the insoluble compound from the reaction mixture by filtration. Another application is in chemical analysis. In qualitative analysis—the determination of the substances present in a sample—the formation of a precipitate is used to confirm the identity of certain ions. In quantitative analysis, the aim is to determine the amount of each substance or element present. In particular, in gravimetric analysis, the amount of substance present is determined by measurements of mass. In this application, an insoluble compound is precipitated, the precipitate is filtered off and weighed, and from its mass the amount of a substance in one of the original solutions is calculated (Fig. 1.6). Gravimetric analysis can be used in environmental monitoring to find out how much of a heavy metal ion, such as lead or mercury, is in a sample of water. [Pg.93]

There are a number of well-documented, validated methods for the analysis of total fibre in food products in the AOAC manual (993.19, 993.23, 991.42, 991.43 and 958.29). Most of these are gravimetric methods where the fibre is precipitated with ethanol and washed and the fibre content calculated after allowances are made for any protein and/or ash that the precipitate contains. These methods rely on precipitation of the fibre with alcohol for their quantification, but as inulin is soluble in mixtures of ethanol and water it cannot be detected in these tests. The most recent method (2001.03) includes an HPLC stage to allow for detection of the presence of maltodextrins, which are poorly digested in the body, but this will not detect inulin. [Pg.257]

Procedures. A standard recipe for the latex preparation is shown below (St + M2) 20 g, (water + buffer) 160 g, and initiator 5 mmole/1. The weight fraction of M2 in monomer charge (f) was varied from 0.01 to 0.50. Polymerizations were carried out at 55°C or 70°C and pH 2.5 or 9.0 under nitrogen. Samples were withdrawn from the reaction mixture at various time intervals and the polymer was precipitated in an excess of acetone. The conversion and polymer composition were determined by gravimetric means and by elemental analysis, respectively. The M2 fraction in instantaneously-formed copolymer ( Fi ) was calculated from eq. 1 ... [Pg.149]

Total Sterol Content. The gas liquid chromatographic method for sterol determination using an internal standard (cholestanol) is used to calculate the absolute (total) sterol content of an oil (68, 69). Gravimetric, enzymatic, colorimetric, and liquid chromatographic methods have also been reported (69). Limits (mg/100 g) are as follows (12) virgin olive oil, refined olive oil, and olive oil (mixture of refined and virgin) >100 crude olive-pomace oil >250 and refined ohve-pomace oil, olive oil and olive-pomace oil (mixture) >180. [Pg.960]

In this method, the vessel is filled with a solute, and a supercritical fluid continuously flows through the vessel. Mild flow rate is used so that the outlet stream is assumed to reach equilibrium, which is then analyzed for the solute concentration by chromatographic, spectroscopic, gravimetric, dielectric, and other techniques. The apparatus used by Bristow et al. (2001) is shown in Figure 9. Here, solute is filled in the sample vessel. Continuous flows of supercritical fluid or a fluid mixture with cosolvent are maintained. For on-line analysis, such as using UV detector, the fluid mixture is bypassed directly to the analyzer for baseline correction, and then the fluid is allowed to pass through the sample vessel. For off-line analysis, the sample is collected in the solvent or cold trap for a given period of time (f), and then analyzed for solute amount. Solubility is calculated as... [Pg.9]

The percent composition of a mixture of NaHC03 and Na2C03 can be calculated from gravimetric analysis data by knowing the following five factors. [Pg.105]

Before polymerization, isoprene was distilled under a flow of argon in the presence of AlO so-C Hgjj and then distilled over a TiCl -Al(/50-catalytic system, which provided a monomer conversion of 5-7%. The polymerization on fractions of the titanium catalyst was conducted in toluene at 25 °C under constant stirring. In this case, the calculated amounts of solvent, monomer, and eatalyst were successively placed into a sealed ampoule 10-12 mL in volume. The monomer and catalyst concentrations were 1.5 and 5x10 mol/L, respeetively. The pol5nnerization was terminated via the addition of methanol with 1% ionol and 1% HCl to the reaction mixture. The polymer was repeatedly washed with pure methanol and dried to a eonstant weight. The yield was estimated gravimetrically. [Pg.30]

The yield of the copolymeric microspheres was determined gravimetrically. After copolymerization, the latex solution was added to 1% calcium chloride solution and centrifuged to isolate the particles from the mixture. The copolymeric microspheres were washed several times successively with water and methanol solvents to remove the remaining monomer and initiator, and then dried in a vacuum oven at 50 °C till attainment of constant weight. The conversion of monomers was calculated by the equation (3)... [Pg.106]

Braeuer, P. Salem, M., and Hatting, P Calculation of single adsorption isotherms from gravimetrically measured binary gas mixture adsorption isotherms on activated carbon at high pressures, Sep. Purif Technol., 12(3), 255-263(1997). [Pg.1001]


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See also in sourсe #XX -- [ Pg.324 ]




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