A gas chromatography apparatus adapted for large scale separation of gases at low temperture comprises a column packed with a solid adsorbent and having a cooling tube being open at both ends extending centrally through its length. The column is suspended in a pressure vessel so that it may be totally immersed in a liquified gas coolant. The pressure vessel has heating means to maintain the coolant at its boiling point and thereby to regulate the temperature within the vessel by varying the pressure therein. The apparatus has particular application to the large scale separation of hydrogen isotopes.