Abstract: A metal working lubricant is disclosed for effective use in the working of metallic materials, particularly in cold rolling, which comprises the components of [I] an alkali metal salt, an alkaline earth metal salt, or a salt or amide of an amine or alkanolamine of a carbon number of 1 to 24, each said salt and said amide being derived from at least one acid selected from the group consisting of (1) an aliphatic mono- or di-carboxylic acid of 8 to 22 carbon atoms, or a polycarboxylic acid thereof, (2) a petroleum sulfonic acid, and (3) a naphthenic acid; [II] an alkylene glycol of the formula HO--C.sub.n H.sub.2n O.sub.m--H where m is an integer of 1 to 3, and n is an integer of 3 to 10; [III] water; and [IV] a mineral oil, a synthetic lubricant, a fat, a fatty oil or a combination thereof.

Abstract: A cold trap disposed in a system in which liquid sodium is circulated as a heat exchanging medium, and adapted for removing impurities from the liquid sodium. The cold trap has a vessel in which defined are a cooling zone for cooling the liquid sodium containing the impurities, trapping zone in which the precipitated impurities are trapped and separated from the liquid sodium and an economizer zone in which the purified liquid sodium is reheated. The cooling zone and the economizer zone are disposed adjacent to each other, so that the purified sodium flowing through the economizer zone may be heated by the liquid sodium flowing through the cooling zone. The trapping zone is disposed in the passage of the liquid sodium interconnecting the heating and economizer zones.