Selected gravimetric method for

Selected Gravimetric Method for Inorganic Cations Based on Precipitation... 

Gravimetric methods for other transition metals are detailed by several authors in reference texts a representative selection of well-known organic reagents and their common analytes is given in Figure 1. 

Coulometric methods are as accurate and precise as conventional gravimetric and volumetric procedures and, in addition, are readily automated. In contrast to gravimetric methods, coulometric procedures are usually rapid, and do not require that the product of the electrochemical reaction be a weighable solid. The methods are moderately sensitive, and offer a reasonably selective means for separating and determining a number of ions. 

Sorption Properties. Sorption isotherms were determined of n-hexane and 2,3-dimethylbutane on variously pretreated samples of zeolite by a gravimetric method using a Cahn electrobalance. No shape-selective sorption was observed for these sorbates, which bespeaks a pore size greater than about 0.5 nm. The sorption capacity of S2 was appreciably lower than that of zeolite X, Y, or mordenite. Routine sorption capacities were determined by a simple procedure of pore filling with benzene at room temperature after calcination of the samples at various temperatures. 

There are five major methods for the determination of fluoride ions m aqueous solution (1) volumetric, (2) gravimetric, (3) null pointpotentiometry, (4) fluoride ion-selective electrode (also known as specific ion electrode), and (5) ion chromatography... 

The principles of solution thermodynamics can be applied to absolute adsorption variables without any of these complications. For absolute variables, which arise naturally in molecular simulation, the pressure is a single-valued function of n, the differential functions exhibit no singularities, and the selectivity approaches a finite value as P —> oo. Absolute adsorption may be determined experimentally by measuring excess adsorption in the usual way (volumetric or gravimetric method) at sub-atmospheric pressure where the difference between absolute and excess adsorption is negligible. 

The reference analytical methods for anions in wines and byproducts are summarized in Table 8.3. They use titrimetric, gravimetric approaches or selective ion electrodes, but today the most performed and extensively used approach for quality control analysis in oenology is ion chromatography. 

Finally, the classical method for the determination of cai bon and hydrogen in organic compounds is a gravimetric volatilization procedure in which the combustion products (H2O and CO2) are collected selectively on weighed absorbents. The increase in mass serves as the analytical parameter. 

A gravimetric method was proposed for Ag and other precious metals, based on reduction with dipyrone (39)121. Determination of Ag(I) ions, strongly complexed with ammonia, sulfite, thiocyanate or thiosulphate, was carried out by potentiometric titration with sodium A.A-diethyldithiocarbamate (11). The titration end-point was better defined when using a sulfide ion-selective electrode (ISE)137. Polypyrrole-based ISEs are poisoned by Ag(I) cations leading to modified selectivities. Ag(I) ions can be implanted... 

Solubility. Solubility-based gravimetric quantification of total cellulose, hemicellulose, and lignin has been by far the most commonly used method for determination of the bulk composition of both archaeological and other old woods. These techniques were developed by wood chemists to isolate, characterize, and quantify the major components of sound wood (3). Although the details of the various isolation methods are beyond the scope of this review, the procedures are based on physical isolation via selective solubilizations of other components, followed by weighing of the residue. 

A variety of techniques have been used to measure the solubility of metal chelates in ScFs, including gravimetric, (45,46) spectroscopic, (36,37,47,46,48) and chromatographic methods. (36,37,45-51). No method is ideal, and the relative merits of these techniques are discussed in the literature. As previously shown, laser induced fluorescence (UF) is a fast, sensitive, and selective method for in-situ determination of uranyl chelates in ScF CO2. In this section we discuss the methods and merits of using LIF to determine solubilities of uranyl chelates in ScF CO2. 

To increase the precision of quantitative analysis, the plasticizer sample is diluted with carbon disulfide, its infrared absorption measured, and compared with absorptions standard of standard samples prepared also in CS2 to cover the range of concentrations from 0.5 to 3 mg/ml. For each suspected (identified) plasticizer, a series of standards has to be prepared and measured. It is also important to select a suitable wavelength for quantitative analysis. For dioctyl phthalate bands at 1725 and 1121 cm" are usually used. For tricresyl phosphate band at 1191 cm is used. Similar to gravimetric method, the results are subject to various interferences when mixtirres of plasticizers or mixture of plasticizers with other additives ate used. 

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