US PATENT SUBCLASS 62 / 639
.~.~ Helium

Current as of: June, 1999
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62 /   HD   REFRIGERATION

600  DF  CRYOGENIC TREATMENT OF GAS OR GAS MIXTURE {4}
617  DF  .~ Separation of gas mixture {3}
639.~.~ Helium

DEFINITION

Classification: 62/639

Helium:

(under subclass 617) Subject matter wherein one of the constituents being separated is helium.