Carbon, determination

Calcium in calcium carbonate. Determine the calcium in an analysed sample of dolomite. Dissolve about 0.38 g, accurately weighed in 1 1 hydrochloric acid, warm gently, filter through a quantitative filter paper, wash, dilute the combined filtrate and washings to 1 L. Measure the calcium content of the resulting solution use a calcium filter. Compare the value for Ca thus obtained with the known Ca content. 

The quality and quantity of sites which are capable of reversible lithium accommodation depend in a complex manner on the crystallinity, the texture, the (mi-cro)structure, and the (micro)morphology of the carbonaceous host material [7, 19, 22, 40-57]. The type of carbon determines the current/potential characteristics of the electrochemical intercalation reaction and also potential side-reactions. Carbonaceous materials suitable for lithium intercalation are commercially available in many types and qualities [19, 43, 58-61], Many exotic carbons have been specially synthesized on a laboratory scale by pyrolysis of various precursors, e.g., carbons with a remarkably high lithium storage capacity (see Secs. 

Pu distribution ratios and dissolved organic carbon determination... 

Carbon. Determination of 8 has been carried out by GC separation of the analytes followed by high-temperature oxidation. Although oxidation with CuO at 850°C has been used, use of NiO at 1050°C supplemented by O2 is preferable, and it is important to remove HjO before isotopic analysis (Merritt et al. 1995). 

Cheng H, Edwards RL, Mttrrell MT, Benjamin TM (1998) Uranium-thorittm-protactinium dating systematics. Geochim Cosmochim Acta 62 3437-3452 Cherdyntsev W, Kazachevskii IV, Kttz mina YA (1965) Age of carbonate determined from the isotopes of thorium and uranium. Geochem Int 2 749-756... 

One of the best-known commercial instruments developed for organic carbon determinations is the Beckman total carbon analyser, which utilises an analysis scheme developed by Van Hall and co-workers [57,99]. This instrument works reasonably well in fresh water. It has become a standard instrument in pollution control and water treatment [103]. The Beckman instrument has not worked as satisfactorily for seawater because of the latter s high carbonate and low organic content. 

Determined by size exclusion chromatography with polystyrene standard in 1,2,4-trichlorobenzene dBranching density per 1000 carbons determined by H NMR... 

Ratio of microbial biomass to total organic carbon Calculation from individual measures Indicates enrichment of microbial biomass relative to total organic carbon determined in nonstandard laboratory with specialized equipment Rice et al. (1996)... 

The character of the adsorbent surface has a major effect on the adsorption capacity and rate. The raw materials and the process used to activate the carbon determine its capacity. 

AlRg groups. The latter assumption is favored by the experience that incomplete reaction of the silanol groups occurs always with trimethyl-silyl chloride. This is caused by steric hindrance (219, 220). Diisobutyl aluminum groups are at least as bulky as trimethylsilyl groups. Therefore, since one aluminum atom is bound for every silanol group, a smaller ratio than two of alkyl groups to aluminum must prevail. No carbon determinations have been made, unfortunately. 

Grosjean, D. Solvent extraction and organic carbon determination in atmospheric particulate matter The organic extraction-organic carbon analyzer (OE-OCA) technique. Anal. Chem. 47 797-805, 1975. 

Table 2.4 Acid fractionation factors for various carbonates determined at 25°C (modified after Kim et al. 2007)...

Figure 28-19 Apparatus for trapping basic or acidic gases by Ion exchange.ffrom a a sterner, "Ion Exchange Resins for Trapping Gases Carbonate Determination," Anal. Chem. 1987, 59,2439.]...

R. Dunn, New Developments in Membrane-Selective Conductometric Instruments for Total Organic Carbon Determination in Water, Am. Lab., September 2004, p. 22. 

B. Wallace and M. Purcell, The Benefits of Nitrogen and Total Organic Carbon Determination by High-Temperature Combustion, Am. Lab. News Ed., February 2003, p. 58. 

The hybridization of a carbon determines to a great extent the range within which its 13C signal is found. As illustrated in Fig. 3.3, sp3 carbons resonate at highest field, followed by sp carbons, while sp2 hybridized centers are shifted farthest to low field. The hybridization effect in 13C NMR thus parallels the effect observed in H NMR. The 13C resonances of sp3 carbons are found between — 20 and 100 ppm relative to TMS sp carbons resonate from 70 to 110 ppm the low field sp2 carbon signals occur at 120 to 240 ppm in organic compounds. 

Biogenic silicon (BSI) was determined, with minor modifications, by the method of DeMaster (17). As adapted, the technique involved time-course leaching of <20-mg samples of particulate matter in 30 mL of 1.0% Na2C03 in a water bath at 85 °C. Silica in leachates was quantified either colorimetrically (Technicon autoanalyzer procedure) or by nitrous oxide flame atomic absorption. A high-temperature catalytic-combustion technique (Perkin Elmer 240C) was used for particulate organic carbon determinations. Particulate inorganic (carbonate) carbon was measured on the same instrument by CO 2 evolution after treatment of the particles with phosphoric acid. 

Section I identified the performance criteria that determine the suitability of a given electrode for an electroanalytical application. We now turn to the question of what aspects of the carbon determine its performance and electrochemical behavior. Since the structure of sp2 carbon materials is more complex than that of pure metals like Pt, there are more structural variables that affect behavior. As a consequence, sp2 carbon can vary widely in conductivity, stability, hardness, porosity, etc., and care must be taken to choose and prepare the carbon material for an electrochemical application. Before discussing particular carbon electrode materials, we first consider which structural variables affect the electrochemical observables discussed in Section II. 

It is discussed above that the nucleobase radical anions can be proton-ated at a heteroatom and/or carbon. Only the heteroatom-protonated species retains reducing properties, and thus the rate of protonation at carbon determines whether or not an ET to 5BrUra is observed under the given condition. Protonation at carbon is especially fast in the case of Guo, and for this reason an ET to 5BrUra was not observed (Nese et al. 1992). A compilation of the rate constants for such ET reactions is found in Table 10.26. As can be seen from this table, the radical anions transfer an electron to 5BrUra at practically diffusion-controlled rates, while the heteroatom-protonated species react two orders of magnitude more slowly. 

Kawata et al. [ 128] have described the effects of headspace conditions on recoveries of volatile organic compounds from sediments and soils. Hewitt [129] compared three vapour partitioning headspace and three solvent extraction methods for the preparation of soil samples for volatile organic carbon determination in soils. Methanol extraction was the most efficient method of spiked volatile organic carbon recovery, which depended on the soil organic carbon content, the octanol-water partitioning coefficients of analytes and the extraction time. 

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