Letters Sent to Dr. F.B. Flinn [Dr. Frederick B. Flinn], July 2, 1925

V A for State 350 Main Street, Orange, N J. July 2, 1925. Dr. F. B. Flinn, 437 West 59th Street, Columbia University, New York City. My dear Dr. Flinn: Each of the four specimens of cheez cloth containing activated zine sulfide which you handed me about a week ago was ignited and the net weight of the zine sulfide ascertained. Alpha pay comparison of the activity of the ignited material showed that the radioactive content was comparable to that of the original material supplied to The Ansonia Clock Works. From the weight of zine sulfide found in the four specimens I have thereby computed the approximate radioactive content in terms of r adium as a standard. Specimen 1. C. Muessener, 1 6 of ZnS painted. Ignited weight, 043 8 containing approximately .0005 ng radium equivalent. Specimen 2. L. Pine, 2 6 of ZnS painted. Ignited weight, .205 6 containing approxiuately .0026 158 radium equivalent. Specimen 3. A. Durkin, 10 6 of ZnS painted. Ignited weight, 342 8 containing approximately .0043 mg radium equivalent. Specimen 4. B Wishinski, 10 8 of ZnS painted. Ignited weight, 512 8 containing approximately .0065 mg radium equivalent. I trust that this data will serve your purpose. Very truly yours, H. H. Barker.