noun \¦ȯ(r)thə+\

Definition of ortho–hydrogen

  1. :  molecular hydrogen in which the two hydrogen nuclei are spinning in the same direction ordinary hydrogen gas comprises an equilibrium mixture of three parts of ortho-hydrogen (with parallel nuclear spin) to one part of para-hydrogen (with antiparallel nuclear spin) — Otto Reinmuth — compare para-hydrogen

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a trip made at another's expense

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