Carbon isotopic mixtures

To extend the study of the apparent decomposition recombination reaction, and specifically to determine if the carbon atoms exchange with other atoms in other acetylene molecules, tests using carbon isotopes were conducted. A mixture of 50% regular acetylene, C2H2, and 50% heavy acetylene. 

The results as shown in Figure 4.19 suggest that there is no source relationship between MW-2 and MW-4. The enrichment of heavy 13C carbon isotope in MW-4 may be attributed to the presence of heavy refined product, originating from an isotopically heavy rich (rich in 13C) crude oil feedstock mixture. 

Other isotopic species, such as boron, carbon, sulfur, and silicon, have been found to be enriched by illumination of isotopic mixtures of respective polyatomic molecules with intense focused C02 laser pulses at 10.6 /tm l 75, 438, 655). 

Separation factors of hydrogen (H2), hydride of deuterium (HD) and deuterium (D2) have been determined for adsorption of hydrogen isotopes mixtures on the samples NPC at temperatures 68 K and 78 K. The values don t extremely large. They are close to ones of active carbons. 

Most elements appear in nature as isotope mixtures. Thus, natural carbon is a mixture of 98.90 % of isotope 12C and 1.10 % of isotope 13C. Table 6.1 lists the abundances of a few elements that are important in organic chemistry. In Appendix 4, the masses and the isotopic abundances are given for all the isotopes except the rare earths. 

In addition to the fact that plants differ in their 6 C values, another factor of major importance in nutritional studies is that the carbon isotope ratios of animal tissues and products (e.g., feces or breath CO2) resemble the isotopic composition of animal diets (15-18). Consequently, by analyzing animal tissue, feces, or stomach contents, it is possible to determine whether an animal s diet consists of C3 plants, Ci, plants, or a mixture of both. In ecological studies, the technique is most useful in situations where C3 and Ci, plants coexist, such as in grasslands or deserts. 

Herbivore diets usually contain adequate amounts of protein as evidenced by the net growth of the animal but the mixture of amino acids derived from vegetation is probably different from that required by the animal Thus herbivores probably synthesize a large proportion of their required amino acids by transamination of keto->acids derived from the carbohydrate part of their diet As a result one would expect that the carbon isotopes of both apatite and gelatin in herbivores would show a direct relationship to the mixture of Co and plants consumed ... 

The techniques used in carbon isotope studies by Abell and Yong were described by Abell et al. (1985). Carbonates (around 120 samples) were analysed by conventional reaction with phosphoric acid. Kerogen (around 250 samples) was extracted with concentrated HCl, rinsed with deionized water and a 5 2 mixture of concentrated HF-HCl (Yong, unpubl. data). 

K. Russe, S. Valkiers, RD.R Taylor (2004) Synthetic isotope mixtures for the calibration of isotope amount ratio measurements of carbon. Int. J. Mass Spectrom. 235, 255-262... 

Na-chloride waters, representing mixtures of Na-bicarbonate waters and Tertiary marine/brackish pore waters. The carbon isotopic ratios vary between -8.7%o and -3.1%o pdb no data for oxygen isotopic composition are available. 

The absence of dolomite cement at sandbody bases and its abundance at sandbody tops, the reported organic carbon isotope signal in the rhombic ferroan dolomite and the mixture of pedogenic dolomite textures and burial diagenetic textures in the sandbodies suggests that options 1 and 4 together are probably responsible for, the distribution of dolomite in the Chaunoy sandbodies. 

The Sr isotope database for saddle dolomite consists of 106 analyses plus a few minimum and maximum values for datasets that were not published in full. Note that none of the sandstone studies reported Sr isotope data, and only four studies of carbonate-sandstone mixtures contain such data (Table 1). As a consequence, the current dataset is of limited significance. Nevertheless, the data depicted in Fig. 9 reveal some interesting aspects. With a single exception, all of the saddle dolomites are more radiogenic than 0.708 and about one-third of the dolomites show ratios > 0.710. Values in excess of 0.7092 reflect precipitation from Sr-enriched pore waters rather than initial (syndepositional) seawater (e.g. Smalley el al., 1994). The current Sr isotope database is biased toward samples from lower Palaeozoic formations (Table 1), a period characterized by relatively high marine Sr/ Sr ratios ( 0.7082-0.7092). 

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