Radioactive tracer such as a cell or tissue, or as a flow tracer to track fluid flow. Radioactive tracers are also used to determine the location of fractures created by hydraulic fracturing in natural gas production. Radioactive tracers form the basis of a variety of imaging systems, such as, PET scans, SPECT scans and technetium scans. Radiocarbon dating uses the naturally occurring carbon-14 isotope as an isotopic label. Isotopes of a chemical element differ only in the mass number. For example, the isotopes of hydrogen can be written as H, H and H, with the mass number at top left. When the
Hydrochloric acid water. However, the speciation of hydrochloric acid is more complicated than this simple equation implies. The structure of bulk water is infamously complex, and likewise, the formula HO is also a gross oversimplification of the true nature of the solvated proton, H, present in hydrochloric acid. A combined IR, Raman, X-ray and neutron diffraction study of concentrated solutions of hydrochloric acid revealed that the primary form of H in these solutions is HO, which, along with the chloride anion, is hydrogen-bonded to neighboring water molecules in several different ways. (In HO, the proton is sandwiched midway between two water molecules