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Table 1 Statistical properties of molar isotope ratios and isotopic equilibrium constants in 285 natural gases and 5 catalytic gases.

From: Natural gas at thermodynamic equilibrium Implications for the origin of natural gas

  Natural Gases Catalytic Gases
  mean sd × 104 V× 106 Mean sd × 104 v× 107
13 C 1 / 12 C 1 0.00991 0.55 5.8 0.00991 0.40 0.30
13 C 2 / 12 C 2 0.02031 1.07 5.2 0.02030 0.63 1.78
13 C 3 / 12 C 3 0.03090 1.50 4.4 0.03090 0.97 1.9
Q 1,2 2.0486 70.6 2.2 2.0481 35.7 5.7
Q 1,3 3.1175 130 3.3 3.1172 30.6 1.8
  1. Natural gas data was taken from USGS Energy Resource Organic Geochemistry Data Base, http://energy.cr.usgs.gov/prov/og/. Catalytic gases are from octadecene decomposition over reduced nickel oxide (180 – 210°C) [18]. C1–C3 compositions were normalized to % wt carbon. δ13C values were converted to mass ratios which were used to calculate wt 13C at each carbon number: x1 at C1, x2 at C2, and x3 at C3. Wt 13C1 = x1; Wt 13C2 is wt C2 with composition 13C12C = x2+((12/13.00335)x2); wt 13C3 is wt C3 with composition 13C12C2 = x3+((24/13.00335)x3). Wt 12C at C2 was calculated as the total wt 12C at C2 minus the wt 12C in 13C2. Wt 12C at C3 was also the total wt 12C at C3 minus the wt 12C in 13C3. Weights (per 100 g) were converted to moles/(100 g C1–C3) which were used throughout our analysis. The quotient Q1,2 = (13C2)*(12C1)/(13C1)*(12C2) and Q1,3 = (13C3)*(12C1)/(13C1)*(12C3), where concentrations are moles/100 g. Variance (v) is (sd)2 for log (ratio).