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    "title": "Report, no date",
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        "Safety Light Collection",
        "Records Related to Radium Dial Painters"
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    "ocrText": "-4-\n6\ninstrument thus corresponds to 0.0000857 div. per sec. This value then really\nbecomes the approximate calibration constant of the Wulf quartz fiber electroscope.\nThe radium content given for each of the other subjects was computed by dividing\nthe observed increase in drift of the fibers by this constant.\nThe exceedingly small increase observed in the drift of fibers when Subje et o\nwas tested is not to be regarded as an accidental effect, for in this case the\nactivity was in part caused by the presence of mesothorium. It will be shown\nlater in the section describing the experiments conducted on detecting radioac-\ntivity by the expired alr method that far smaller amounts of mesothorium can be\ndetected in the expired air of subjects than radium. In testing the expired air\nof Subject C, the presence of mesothoriun was established with certainty.\nAt this point we wish to call attention to some special precautions that\nmust be observed in making gamma-ray measurements on persons working in labora-\ntories where radium is being refined or workers handling luminous materials con-\ntaining radium or mesothorium. The clothes of such persons not infrequently\ncarry traces of radium and its presence may introduce large errors in the mea-\nsurements. Before accepting a subject for tests, a thorough cleansing bath is\nrequired including a hair shampoo and a complete outfit of inactive garments must\nbe worne In one case where a positive test for radioactivity was detected when\nthese precautions had all been observed, it was discovered that the pendant on\na necklace worn by the subject was radioactive and that the trace of radium thus\ncarried was entirely responsible for the observed activity.\nMEASUREMENTS WITH DIFFERENT TYPES OF ELSCTROSCO^ES.\nOur investigations include extended expariments with several types of elec-\ntroscopes which all demonstrate conclusively that the observed small increaseSin\ndrift are directly proportionel to the activity of the radioactive source. These\nexperiments were not conducted with active subjects but with normal inactive in-\ndividuals who carried on their persons small ampoules containing standard solutions\nof radium. In most of the experiments, the small ampoules of radium solution"
}