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    "id": "75730982",
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    "contentType": "document",
    "title": "Report, no date",
    "citationUrl": "https://catalog.archives.gov/id/75730982",
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        "Safety Light Collection",
        "Records Related to Radium Dial Painters"
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{
    "seq": 14,
    "pageIndex": 0,
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    "ocrText": "-12-\n14\nAfter standing for an hour the natural drift of the instrument with the expired air\nin it was taken again and found to have returned to normal, 0.060 divisions per\nsecond, the value found before the expired air was introduced. It is seen at a glance\nthat the net drifts given in the last column of Table IV identify with certainty the\npresence of thoron in the expired air whose source is evidently mesothorium. The\nfact that the natural drift resumed normaley after an interval of six minutes and\nshowed no rise in the course of an hour indicates that radium was not detected.\nWe\nshall point out later that the quantity of radon in the expired air is so small\nthat\nit may easily escape detection by this method of testing.\nThe presence of radon in the expired air of Subject B was established by tests\nmade with a large chamber, 3 liter, Lind instrument, on three different dates.\nIn\none of the tests the expired air was first collected in a Douglas gas bag and a few\nhours later 3700 ac of it were drawn into the chambere In the other tests the ex-\npired air was forced directly through the drying and filtering trains connected in\nseries with the testing instrument. After the thorium emanation also present had\ndecayed\n,readings of the drift were taken at half hour intervals for four hours. The\nnet drifts although small showed the normal rise characteristic of radon; and after\nwashing out the chambers with atmospheric air the usual marked drop in drift was\nobserved. In one of these tests the observed drift at maximum, three hours after\nintroduction of expired air was 0.0287 divisions per second.\nThe initial natural\ndrift was 0.0128 divisions per second, making the net drift 0.0159 divisions per\nsecond. The average value of the net drifts in the three tests was 0.0128 divisions\nper\nsecond.\nSince the calibration constant of the instrument employed in these\ntests was 7.3 X 10-9, meaning that 7.3 X 10-9 curies of radon produced a net drift\nof one division per second, we find the quantity of radon in 2.7 liters of expired\nair to bes\n0.0128 X 7.30 X 10-9 \" 93. X 1012 curies\nThis number represents the quantity of radon expired by Subject B in 18 seconds,\nwhence the radon expired per second will be,\n93 X 1012 = 5.2 x 10-12 curies\n18"
}