Thermally insulating containers or the Dewar containers useful for shipping and storage of low-temperature liquefied gases, having double walls made of a metal, the space between the walls being evacuated, are provided, the thermal insulation properties of which are prevented from deterioration by putting in the vacuum space, a getter alloy composed of a ternary alloy expressed by the formula LaNi.sub.x Cr.sub.y, where x is a number from 1 to 6, both inclusive and y is a number from 0.1 to 2, both inclusive, working to adsorb traces of hydrogen coming out of the wall material. The alloy is preferably an activated one. The vacuum thermal insulation can further be improved by the presence of an adsorbent having a large specific area which serves to adsorb traces of gases other than hydrogen.