TABLE I. TABLE II. Time. I. Time. I. Days. Days. 0 16·2 0 0·8 0·6 25·4 0·7 13 1 27·4 1 18 2 38 1·9 26·4 3 46·3 6 46·2 4 54 10 55·5 6 67·5 14 64 10 84 18 71·8 24 95 27 81 57 100 36 91 50 95·5 57 99 84 100 I made several other series of determinations, but the results did not agree well. The effect of heating does not persist when the heated radium compound is dissolved. Of two specimens of the same radium compound of activity 1800, one was strongly heated and its activity thereby reduced to 670. The two portions being now dissolved and left in solution for twenty hours, their initial activities in the solid state were 460 for the not heated portion and 420 for the heated one; the difference between the two portions was therefore not considerable. But if the two products do not remain for a sufficient length of time in solution—if, for example, they are evaporated to dryness, immediately after solution—the not heated product is much more active than the heated one; a certain time is necessary in the dissolved state for the effects of heating to disappear. A product of activity 3200 was heated, and its activity thereby reduced to 1030. This product and a similar portion which had not been heated were simultaneously dissolved, and the two then immediately evaporated to dryness. The initial activity was 1450 for the not heated portion, and 760 for the heated one. [Illustration: FIG. 13.]