Letters Received to H.H. Barker, June 10, 1929

TREASURY DEPARTMENT UNITED STATES PUBLIC HEALTH SERVICE OFFICE OF INDUSTRIAL HYGIENE WASHINGTON, D. C. JUN 111929 AND SANITATION Room 1-123, "C" Bldg. 16 Seventh St. , S. W. June 10, 1929 Mr. H. H. Barker, Vice President, U. S. Radium Corpn., 535 Pearl St. New York, N. Y. Dear Mr. Barker: You will recall that in our studies on effect of radium on workers in watch factories one of the things we propose to do is to determine the radio active content of the air in the workrooms. For this purpose we pre- pose to suck the air through cotton wool and incinerate it and place the residue inside an ionization chamber and de- termine the amount of ionization due to it. In connec- tion with this we have asked Dr. Curtis of the Bureau of Standards to calibrate the ionization chamber for solids which we propose to use for this purpose. Question has arisen as to the best method of calibrating the chamber and he proposes to colibrate it by placing a known quantity of radium sulphate in the chamber and determining the rate of deflection of the leaf for it. Do you think this would be a satisfactory method of calibrating the chamber? The reason for using radium sulphate is that Dr. Curtis says when the radium salts are mixed with the paint they become converted into radium sulphate and that this probably is the substance which is present in the dust in the air. Do you think this is SO? It occurs to me