XLRAYS ON ENZYMES . III . A UmT oF M ~ , AS ~

In our studies on the radiochemical reaction effeeted by the radiations (beta and gamma) from radium emanation in which enzymes are inactivated we have stated that in a given system the chemical change is a function of the product of two variables; namely, the average amount of emanation present, Eo, and time, t. Theproduct of these two variables has been equated to a single variable, W, for which we have employed the expression "millicurie hours" as a unit of measure. This is not, however, a suitable unit of measure of the quantity of energy which W represents. That no other expression has been available is due to the circumstance that up to the present time bu t little attention has been given to making clear a distinction between activity and amount of radium emanation. The curie is defined as the amount of emanation in equilibrium with 1 gin. of radium element. In our experiments we are concerned not only with the amount of emanation but more particularly with the activity or power 1 of the preparation, for which no unit has yet been assigned. In this communication we shall endeavor to show the desirability of having such a unit and suggest what appears to us to be one that will meet our