Letters Sent to C.H. Granger, June 3, 1927

June 3rd,1927. Mr. c. H. Granger, Supt.) Waterbury Clock Company, Waterbury, Conn. Dear Mr. Granger: Please accept our thanks for your letter of June lst. We know there has been a great deal of discussion over the relative properties of radium and mesothorium, and the Doctor in Waterbury who pronounced himself so strongly on the question of radium not being poisonous and blaming any possible injuries on mesothorium is probably not speaking from a scientific knowledge which he has, but from more or less hearsay. Now from a physical and chemical standpoint there is no difference in the action of these two materials. There may be a slight difference in the length of the alpha rays, but radium and meso- thorium are isotropic and if once mixed one cannot be separated from the other. As a matter of fact the only way you can tell mesothorium from radium is by a series of measurements, and this is determined by the fact that mesothorium loses its emanating ower much more quickly than radium. The best of physicists and chemists will verify this statement. A great deal of the unfavorable impressions agninst mesothorium is on account of the statement that it is many times more powerful than radium. This statement is absolutely true, if you should take any given weight of pure radium salt and compare it with a like weight of pure mesothorium salt. The mesothorium is approximately 250 times as active. On account of this great activity it will destroy itself, so to speak, in a period of time 1/250ths of the time that it requires radium to destroy itself. Now the joke of the whole matter is - and this is what the doctors do not know, that when you refer to E milligram of mesothorium, you refer to a quantity which has the same amount of emanating power as one milligram of radium. In other words mesothorium is sold and used in terms based upon its equivalent activity to a milligram of radium. It would take 250 milligrams of pure mesothorium to weigh as much as one milligram of radium. I perhaps may be a little crude and not scientific in trying to explain this to you, but trust that you will at least under- stand what I am driving at. Since early last fall we have used no radio-activity in our luminous material except pure radium. For approximately one year. before we went to a straight radium basis we used a mixture of mesothorium and radium in varying proportions, which would average about 60% mesothorium