Studies with the liquid hydrogen and air calorimeters

The calorimeter employed in the following experiments was similar to that described in my paper on “The Scientific Uses of Liquid Air,” and in an improved form in Madame Curie’s work “Recherches sur les Substances Radio-Actives,” 2nd edition, p. 100. A sketch of the apparatus appears in my paper on “The Absorption and Thermal Evolution of Gases Occluded in Charcoal at Low Temperatures.” The arrangement employed consists essentially of a large vacuum vessel capable of holding 2 or 3 litres, into which is inserted a smaller vacuum vessel of 25 to 50 c. c. capacity constituting the calorimeter, the latter being sealed on to a long narrow tube which projects from the mouth of the exterior vessel, in which it is lightly held by a loose packing of cotton wool. A little below the upper end a branch tube is taken off which conveys the volatilised gas from the calorimeter to the gas receiver. To the extremity of the projecting tube a small test-tube, to hold the portions of substance experimented on, is attached by a short piece of rather wide rubber tubing which forms naturally a movable joint that can be bent into any position. With care I have found this valve gives as good results as more elaborate means of securing the dropping of the substances into the calorimeter. A small vacuum vessel which may contain either solid carbonic acid, liquid ethylene, or liquid air, into which the test-tube is placed, cools the materials to different temperatures below those of the laboratory; or alternatively the substances may be heated in the vapour of water or other liquids.