41. There is a known variation in the isotopic abundance of chlorine-37. 42. Since it does not involve isotopic labeling, the results cannot be quantified. 43. This is particularly relevant when employing an isotopic label. 44. Isotopic labeling experiments are commonly considered to be a type of crossover experiment.45. Future isotopic analysis of small, juvenile dinosaurs will better resolve this question. 46. This phenomenon is known as Natural Isotopic Fractionation ( see Figure 3 ). 47. Various subsequent processes then alter elemental and isotopic ratios. 48. Obviously ?M is depends on the precise isotopic composition for a given molecule. 49. Isotopic fractionation in the hydrologic cycle for more details]50. Comets and terrestrial water have similar isotopic ratios.
