Letters Received to H.H. Barker, November 6, 1928

UNIVERSITY OF MISSOURI COLUMBIA DEPARTMENT OF CHEMISTRY No vember 6, 1928 NOV 9 1928 Mr. H. H. Barker United States Radium Corporation 535 Pearl Street New York City My dear Barker: Last evening I wired you stating that it will be possible to attend the examination of the girls during the week of November 19. I shall, however, not be able to leave Columbia until late Friday evening or Saturday morning, and I shall there- fore have to miss the football game, much to my regret. As soon as I know more definitely about train service I shall let you know. I hope, however, to have a good visit with the Underwoods. Tomorrow or day after I expect to return to you one of the spinthariscopes fitted with zinc sulfido screen whose natural scintillations are considerably lower than the usual specimens of zinc sulfide show. We shall send at the same time a sample of Hammer Special Zine Sulfide and a sample of Grade A, furnished by the Denver Fire Clay Commany. The screen which you will find mounted in the instrument is Hammer Special Grade. Grade A appears to be somewhat more free from natural scintillations than the Special. After some experimenting we finally found that at least some of the screens which we had prepared and* con- demned were not so bad as we had suspected. We found that one of the spinthariscopes which you sent is infected, and this was the one which we used in our tests. It is barely possible that this instru- ment became contaminated with a trace of radioactive material in our laboratory. The natural scintillations of the instrument which we are planning to send you will be about 50 in three to four minutes - 5min when Hammer Special is used, and about 25 when Grade A is used. The fluctuations, however, are large and believe that this is in part due to a slight contamination with radioactive matorial of the sample tested. We have also gone over the data which you sub- mitted on the radium content of the excreta in the Dunn case, and we have placed your results alongside of the values found for the radium content of the excreta in the Dumschott case and we find that your values are about 10 times as high when expressed as grams radium per grams dry residue as our values for Mrs. Dums ghott; so I wish to ask whether there is a chance that you may have the decimal point mis- placed in your calculations. Our most active specimen we found to contain 3.8 X 10-10 grams radium per gram, "while you report in the