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    "localId": "75723418",
    "label": "Report, November , 1928",
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    "title": "Report, November , 1928",
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    "collections": [
        "Safety Light Collection",
        "Records Related to Radium Dial Painters"
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    "ocrText": "- 2 -\n7.3 X 10-9 curies of radon. The volume of the ionization chamber is approximately\n2700 cc.\nIn making the gamma ray measurements, the procedure was essentially the same as\nthat followed by Flinn and Schlundt at the time the tests were made on the subjects in\nNewark. The Wulf instrument was set up near the edge of a table about 36 inches high.\nThe subject under test was seated on a chair plus three inch air cushion, with back\ntoward table. The instrument was located a little below the middle of the back of the\nsubject, but not quite as close to the subject as we succeeded in setting the instrument\nin\nthe Newark measurements. It was probably located 2 to 4 inches lower down the back\nthan in the set up at Newark. The fibers of the Wulf were charged positive by means\nof a dry battery, the case being connected permanently to the negative terminal of the\nbattery. Since I observed during the course of the experiments that the natural drift\nslowed down as the potential of fibers dropped, care was exercised in making all read-\nings, for each subject over the same part of the scale, namely, 40 to 25, or 40 to 30.\nAt Newark scale readings were taken as a rule from 70 to 50 on the scale, and the fibers\nwere charged negative by touching them with a charged vulcanite rod. Present data\nindicate that the natural drift of the instrument is practically constant over the\nscale between 70 to 50, when fibers carry a negative charge. AT Newark a single de-\ntermination of drift was made with each subject by two observers noting independently\nthe time required for fibers to pass over certain intervals of the scale. In the\npresent series of tests two determinations of drift were made on most of the subjects\nby each observer, thus insuring greater accuracy.\nGenerally while the gamma ray measurements were in progress the expired tests were\nstarted. Dr. Failla would have the subject blow air from lungs through the ionization\nchamber of his testing apparatus. The expired air for all tests was dried by first\npassing it through a tube containing fused calcium chloride. Each of the subjects\ngave a positive test by this method.\nNext the air expired was blown through the ionization chamber of the Lind elec-\ntroscope, usually for two minutes. With leaf charged it was easy to detect the pre-"
}