Patent classifications
C
CHEMISTRY; METALLURGY
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C01
INORGANIC CHEMISTRY
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C01B
NON-METALLIC ELEMENTS; COMPOUNDS THEREOF;; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
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21/00
Nitrogen; Compounds thereof
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C01B21/04
Purification or separation of nitrogen
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C01B21/0405
Purification or separation processes
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C01B21/0411
Chemical processing only
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