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        "Safety Light Collection",
        "Records Related to Radium Dial Painters"
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    "seq": 11,
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    "ocrText": "-9-\n11\ntesting is equivalent to the radon which is retsined in situo, while the quantity\nof radon which appears in the explred air represents that traction of the radium\nwhich escapes detection by the ganna-ray method of testinge\nBence, the total\nradium present in the living subject is the sum of the values moasured by the\ngamma-ray test and that found in the expired airo In the cases which have come\nunder our observation, the frection of the emanation produced which finds its way\nan\ninto the expired ray did not exceed three per cent.\nIn the experiments 80 far conducted we have made no attempt to concentrate\nthe minute traces of radon in expired air of slightly ralloactive subjects by con-\nmy\ndensing it iseans of liquid air, or absorption in cooled charcoale\nFor the detectio n of radon in the expired air of a subject we found very\nservicaable an air-tight ionization chamber of three liters capacity fitted with\ninlet and outlet cocks. The chamber was made to fit a Lind interchangeable elec-\ntroscope head. The atmosphere pir in the instrument was replaced by exhaled air,\neither, by having the subject blow air directly through the chamber for a minute\nor two, or, the strong walled ionization chambor, exhausted beforehand on a good\nvacuum pumo, was filled with expired alr which had been collected in a Douglas\ngas bage In both methods the expired air before entering the testing chomber\nwas dried and filtered by passing it through two towers filled with coarse calcinm,\nchloride (fused) and then through a tube loosely packed with cotton.\nBefore introducing expired nir the natural drift of the instrument must be\ntaken. Tha electrode system should be kept charged for about 20 minutes before\nrendings ara made, and here again readings must always be taken over the same\npart\nof\nthe\nscale.\nWhen expired air is tested which has beon stored for even a\nany\nfow minutes before it is introduced into the instrument, Observed increase in\ndrift generally indicates the presence of the radon, since thoron whose half\nperiod of decay is only 54.5 seconds can only be detected in expired alr\nby blowing the air directly into the chambere In either case readings of the"
}