ABSTRACT
The heating effect of 30 milligrams of radium bromide was first measured in a special form of differential air calorimeter. The radium bromide was then heated in a glass tube to a sufficient temperature to drive off the emanation occluded in it, and this emanation condensed in a short glass tube immersed in liquid air. The tubes containing the radium and the emanation were then sealed off, and the heating effect due to each tested separately at definite intervals. It was observed that the heating effect of the de-emanated radium decreased for the first few hours to a minimum corresponding to about 30 per cent of the original heat emission. The results indicate that a large proportion of the heat emitted from the emanation tube is due to the matter which causes excited activity. It is a difficult experimental problem to isolate the heating effect produced by the emanation from that due to the secondary products which arise from it.
