Letters Sent, April 7, 1932

April 7,1932. Dr. S. C. Lind, Director University of Minnesota, School of Chemistry Minneapolis, Minn. Dear Dr. Lind: Under separate cover we are shipping you various adhesives to be used in connection with applying phosphorescent zine sulphide to glass surfaces. Your letter does not specify whether you enticipate using this material on the interior surface of a glass sphere or on a flat plate, but I rather infer that it is the former. If such be the case the procedure would be to clean the glass ball thoroughly, place the desired amount of phosphor- escent zine sulphide in same and then add sufficient adhesive #7, mix with the sulphide thoroughly, and then rotate the ball to give an even distribution over the surface - occassionaly blowing a little air into the ball to displace any saturated air inside the ball. We find this prodedure gives a very even distribution of the zine sulphide inside the surface of a sphere. In case you wish to apply the material to 8 flat gless plate, we do not recommend the use of adhesive #7, as it dries entirely too rapidly. Adhesive #3, together with thinner for same, should be used for this purpose. Place your zinc sulphide in & small crucible, add sufficient adhesive to give it sticking qualities, and then thinner to give it consistency to apply readily. If we can be of any help in the preparation of your plates for you please be assured that we shall be glad to do so. In connection with the death of E. M. Byers, caused by the drink- inf of Radiothor, which was an aqua solution of radium and mesothorium: I have recently taken occassion to make a few simple calculations to determine the amount of radon that one would have to ingest in order to have 8 sufficient deposit of radium D in the system to act as a source of supply for polonium. lly calculations were based upon a device which is now being sold, and guzranteed to deliver 7000 Mache Units per day. If we make a hypothetical assumption that the human system would act as a hermetically sealed unit, thereby retaining all radon ingested, we would find that after a period of 20 days the system would contein approximately an equilibrium quantity of 40,000 Mache Units or 16 Micro Curies. Taking into consideration the breaking down of this quantity of radon withthe formation of radium D, and the production of polonium from radium D,with albna rays the emission/from pólonitm, I figure that after a period of one year has elapsed, the alpha rays which would result from the polonium as a result of the