I've recently become interested in chemistry, and have some questions about water.

I've heard of semi-heavy, heavy, tritiated, and oxygen-heavy water. However, what about various combinations of isotopes? Let's say: Oxygen 15 + Tritium? How about Oxygen 18 + Deuterium?

Would these all have distinct properties from one another? Have all the stable combinations been extensively studied and lab tested?

  • 6
    $\begingroup$ Oxygen-15 has half-life of about 2 minutes... $\endgroup$
    – Mithoron
    Jul 21, 2017 at 20:58
  • 1
    $\begingroup$ @Mithoron That's true, but water Oxygen-15 is used to measure tissue or tumor blood flow/perfusion. I'm more curious about the physical differences between the different combinations of isotopes rather than the practicality of making it. $\endgroup$ Jul 21, 2017 at 21:45
  • $\begingroup$ Yeah it's used in PET, but you can't get macroscopic amounts of its compounds. $\endgroup$
    – Mithoron
    Jul 21, 2017 at 22:15
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    $\begingroup$ Because of the dynamic equilibrium of autoprotolysis of water ($\ce{H2O <<=> H+ + OH-}$ the isolation of water with mixed isotopes of H (like pure HDO, or HTO) is hampered. From a probabilistic approach, the natural abundance of $\ce{^2H}$ equals to 0.02% and the one of $\ce{^{17}O}$ to 0.04%. In other words, only 0.000016% chance to encounter a molecule of $\ce{D2^{17}O}$ outside a scientific lab, and expensive (medicalisotopes.com/product-category.php?id=2) For molecules consisting of short-living isotopes, you will need a rapid characterization, mass spectroscopy may be one. $\endgroup$
    – Buttonwood
    Jul 21, 2017 at 22:38
  • $\begingroup$ They would vibrate differently (in terms of frequency) leading to slightly different boiling point and kinetic properties. That's kind of it. $\endgroup$
    – jheindel
    Jul 31, 2017 at 2:29


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