Carbon:sulfur ratio

Figure S. Carbon sulfur ratios (wt/wt) in three cores from the north basin of Little Rock Lake. Carbon and sulfur concentrations were determined by LECCO analyzers. Cores were collected at 5 m (NB-5), 7 m (NB-7), and 9 m (NB-9). The two shallow cores are from epilimnetic sites at which the overlying water remains oxic throughout the year. The bottom water at NB-9 is anoxic in late summer.

Radiotracer analysis is particularly effective for tracking the fate of additives, because molecular fragmentation can typically be expected to result in an impurity element distribution different from that of the original molecules. For example, in nickel plating in the presence of thiourea, complete incorporation of the molecule should give a carbon/sulfur ratio of 1.0, while experiments indicate a ratio ranging from 0.01 to 0.7 depending on the deposition conditions [130,131,141,142], As with additive incorporation, the decomposition process can be a sensitive function of the co-adsorbates [145, 149, 150]. 

Carbon/Sulfur Ratios of Plant Residues as Indicators of Mineralization and Immobilization Processes... 

FIGURE 17.37 Vertical distribution of carbon sulfur ratio (C S) in soils at impacted and unimpacted sites in the WCA-2A (Bates et ah, 1998.). 

Various workers have discussed the determination of total alkalinity and carbonate [ 10-12], and the carbonate bicarbonate ratio [ 12] in seawater. A typical method utilises an autoanalyser. Total alkalinity (T milliequivelents per litre) is found by adding a known (excess) amount of hydrochloric acid and back titrating with sodium hydroxide solution a pH meter records directly and after differentiation is used to indicate the end-point. Total carbon dioxide (C milliequivelents per litre of HCO3 per litre) is determined by mixing the sample with dilute sulfuric acid and segmenting it with carbon dioxide-free air, so that the carbon dioxide in the sample is expelled into the air segments. The air... 

Under the usual commercial hydrodesulfurization conditions (elevated temperatures and pressures, high hydrogen-to-feedstock ratios, and the presence of a catalyst), the various reactions that result in the removal of sulfur from the organic feedstock (Table 4-3) occur. Thus, thiols as well as open chain and cyclic sulfides are converted to saturated and/or aromatic compounds depending, of course, on the nature of the particular sulfur compound involved. Benzothio-phenes are converted to alkyl aromatics, while dibenzothiophenes are usually converted to biphenyl derivatives. In fact, the major reactions that occur as part of the hydrodesulfurization process involve carbon-sulfur bond rupture and saturation of the reactive fragments (as well as saturation of olefins). 

Seston Sulfur. Much of the sulfur that is immobilized by assimilatoiy uptake or dissimilatory reduction is oxidized and reenters the water column as sulfate. We have approached the question of seston-S recycling by comparing carbon/sulfur (C/S) ratios in seston and sediment and by following the fate of 35S in labeled algae added to laboratory sediment-water microcosms. 

Table II Carbon, sulfur, nitrogen and iron elemental data of kerogens (containing pyrite) isolated from Nflrdlinger Ries core samples. H/C, N/C and SQrg/Corg are atomic ratios.

Thioaldehyde S-oxides behave as dienophiles with 1,3-dienes [241]. Cycloaddition involves the carbon-sulfur double bond of the heterocumulene to furnish dihydro-2H-thiapyran S-oxides (Table 6, entry 1). The cis trans product ratio was found to depend upon the initial diene/sulfine ratio. A large excess of diene selectively provided the cis cycloadducts, as a result of a stereospecific reaction of the (Z) sulfine. With a produced proportion of diene, mixtures of cis trans isomers are obtained, with a preference for the cis compound. The Italian authors have demonstrated that the slower reaction allows a (Z) to (E) isomerisation of the sulfines prior to addition. 

Catalyst particles with diameters of about 0.3—0.6 mm were found to be suitable to avoid significant transport limitations. Stabilization of the PR-F catalyst was performed by running the pre-reforming reaction at high steam to carbon molar ratios (>2) at 763 K and 40 bar over a period of 582 h. SEM-EDX data indicated that the surface was sulfur and carbon free after this treatment. 

An interesting asymmetric carbon-sulfur bond formation occurs during the interaction of thiofenchone-S-methylide 21 with 1.1 equivalents of thiophenol in tetrahydrofuran. Two thioac-etals 22 are formed in 94% yield. The ratio of diastereomers, originally 7 3, is reversed to 1 9 on contact with silica gel. It was suggested that the latter ratio refers to the equilibrium139. 

Comparison of Heavy Oils with Bitumen. Many of the analyses indicate that the heavy oils are very similar to the original bitumen. Hydrogen-to-carbon atomic ratios are in the range of 1.65-1.69, which is similar to the bitumen (1.64). Nitrogen and sulfur contents are similar to values for the bitumen (see Table I). Nickel concentrations of heavy oils are slightly lower than the concentration in the bitumen. Vanadium analyses for heavy oils range from lower than to higher than vanadium in the bitumen. 

Figure 6 Volatile/refractory element ratio-ratio plots for chondrites and the silicate Earth. The correlations for carbonaceous chondrites can be used to define the composition of the Earth, the Rb/Sr ratio of which is well known, because the strontium isotopic composition of the BSE represents the time-integrated Rb/Sr. The BSE inventories of volatile siderophile elements carbon, sulfur, and lead are depleted by more than one order of magnitude because of core formation. The values for Theia are time-integrated compositions, assuming time-integrated Rb/Sr deduced from the strontium isotopic composition of the Moon (Figure 8) can be used to calculate other chemical compositions from the correlations in carbonaceous chondrites (Halliday and Porcelli, 2001). Other data are from Newsom (1995).

Carpenter S. J. and Lohmann K. C. (1997) Carbon isotope ratios of Phanerozoic marine cements re-evaluating the global carbon and sulfur systems. Geochim. Cosmochim. Acta 61, 4831-4846. 

Pyrolysis products of chlorinated polyethylene contain molecules similar to those found in polyethylene pyrolysates and, in addition, compounds similar to that obtained from vinyl chloride (significant amount of HCI). Chlorosulfonated polyethylene typically contains only about 1.5% sulfur, but sulfur-containing compounds such as SO2 can be detected among its pyrolysis products. The distribution of chlorine atoms in chlorinated polyethylene has been investigated using Py-GC [55, 56]. The polymer was considered equivalent with a terpoiymer poly[ethylene-co-(vinyl chloride)-co-(1,2-dichloroethylene)]. The level of specific degradation products such as aromatic molecules (benzene + toluene + styrene + naphthalene), chlorobenzene, and dichlorobenzenes correlates well with the carbon/chlorine ratio in the polymer. 

---