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        "Safety Light Collection",
        "Records Related to Radium Dial Painters"
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    "ocrText": "EXPERIMENTAL DETERMINATION OF THE RADIUM PRESENT IN LIVING PERSONS.\nCalibration of Gamma Ray instrument. Mr. Barker and Dr. Flinn worked\nout this 8 method of calibrating the gamma ray electroscope used for detecting radio-\nactive elements in the living persons. They find that a net discharge of the in-\nstrument of 0.0018 d.p.sec. represents 10 micrograms of radium, distributed in the\nbody. This value for the calibration constant applies when the instrument is put\nup close to the middle of back of subject and the net drift of the leaf of the elec-\ntroscope is determined and expressed in divisions per second. TO get this value\ngamma ray measurements were made as just stated on a radioactive subject a few\nmonths before death. After death the radium content of the skeleton and body\nthe\nparts was determined where by the emanation method, and the total radium content of A per-\nson computed Net discharge for radioactive person/0.018 X 10 = micrograms\nradium in living person.\nIn this way it was found that 10 micrograms of radium in a living person produced\na discharge of 0.0018 d.p. sec. in the instrument whence an experimental value 0.8.\nof 0.0072 d.p.sec. for the net drift would represent 40 micrograms of radio-activi-\nty in the individual under test. It may be of interest in this point to mention\nthat two ampoules of radium solution of five micrograms each likewise produce a\nnet drift of 010018 d.p.sed. when placed in the vest pockets of a non-radioactive\nperson of average size.\nLet us compute next the quantity of emanation that would be expired con-\ntinuously from a radio-active person with 40 micrograms of radium present:\nFirst let us generously assume that all of the emanation produced is given\noff in the lungs to the expired air. Since 1 to radium element produces constantly\nper second 2.1 X 10⁻⁶ curies of emanation, i.e., Ra.Em. accumulates at the rate of\nPage -2-\n2.1 X 10⁻⁶ curies per second, it follows that the amount of radium emanation present\nin 1 liter of expired air,--two good breaths--will be-- 6 X 2.1 X 10⁻⁶ X 40 x 10⁻⁶ =\n504 x 10⁻¹² curies, where 6 stands for the time it takes for two breaths. (Hence\nper microgram of radium in the person under test the emanation expired is 12.6 x 10⁻¹²\ncuries.)\nNext calculate the discharge that this amount of emanation will produce in\na Lind electroscope whose calibration constant is 10 X 10⁻⁹ curies emanation.\nEvidently the net drift is given by:\n504 X 10-12 = - - 50.4 X 10⁻³ d.p.sec. or\n10 x 10-9\n- = 0.0504 div. per sec.\nWhen a Lind chamber of only 500 cc capacity is used the net drift will be 0.0252 or\nper nuerogram\n0.00063 d.p.secy. assuming that the calibration constant of the smaller chamber is\nthe same. Using a chamber of 4 liters capacity with same constant, 40 microgram of\nradium (40 X 10⁻⁶ curies) produces a net drift of 0.2016 d.p.sec.\nIn the test Dr. Flinn and I made on Mrs. Dumschoff in Naugatuck, yesterday,\nApril 23, 1928, we found by gamma ray instrument a net drift of 0.00752 d.p.sec. (or\n7.5 X 10⁻³ d.p.sec.) which represents nearly 42 micrograms of radium in her body.\nThree liters of expired air from Mrs. D. in a Lind Chamber, constant esti-\nmated to be 10 X 10⁻⁹, produced a net drift at maximum of 0.021 d.p.sec.\nHence amount of Rn. present = 10 X 10⁻⁹ X .021 = 2.1 X 10⁻¹⁰ curies.\nEmanation produced by 40 micrograms of Ra in 18 seconds, the time taken\nto expire 3 liters of air, is given by - 18 X 40 X 10⁻⁶ X 2.1 x 10⁻⁶= 1512 X 10⁻¹² curies\nThe quantity of radium found by expt. in 3 liters of expired air in this case was\n210 x 10⁻¹² curies. Hence the percentage of emanation which escapes in breath is:\n210 X 10⁻¹²\n= 210 = 13.9%\nThis value X seems normal, 1512 but probably still toohigh\n1512 10⁻¹²\npage -3-\nNow referring back on page 2, to the value 6.3 X 10⁻⁴ d.p.sec. discharge per\nmicrocurie of the emanation in the electroscope, based on the idea that all generated\nis expired, let us see what the actual amount, which we will call 1/8 of the total,\nwill produce in the way of discharge. Evidently the net drift will not be more\nthan 1/8 of 6.3 X 10⁻⁴ = 8 x 10-5 d.p.sec. This is the value in the 1/2 liter\nchamber. For 10 micrograms the actual net drift would be proportional, and numeri-\ncally is 8 X 10-4 d.p.sec. = 0.0008 d.p.sec., in other words we may say that in\npractice 10 microcuries produce a net drift of 0.0008 d.p.sec. Now note that in the\ngamma ray instrument used for these tests 10 micrograms Ra in a person produce a net\ndrift of 0.0018 d.p.sec., which is about twice as great an effect. looking at the\nmatter in this way then we see the gamma ray methodx is actually fully as sensitive\nas the emanation method.\nANOTHER COMPARISON OF THE SENSITIVENESS OF THE GAMMA RAY METHOD AND THE\nEXPIRED AIR METHOD OF TESTING FOR RADIUM IN A LIVING RADIOAC*\nTIVE PERSON.\nFor the Lind instrument assume that we can detect positively a net drift of\n0.002 dep.sec. What quantity of emanation is then present in the electroscope?\nThe answer to that is: 0.002 X 10 X 10⁻⁹ = 2 x 10⁻¹¹ curies = 20 X 10⁻¹² curies.\nSuppose we had used the chamber 1/2 1. capacity. What quantity of radium\nwill in 3 sec. produce this emanation? 1 microgram Ra. produces in 3 sec.\n1 X 10⁻⁶ x 2.1 X 10⁻⁶ x 3 = 6.3 x 10-12 curies. To get the detectable quan-\ntity, 20 X 10⁻¹² curies, will take as many microcuries as 6.3 X 10 -12 is contained\ninto 20 X 10-12 =\n20 x 10⁻¹² = 3.1 microcuries.\n6.3 x 10-12\npage -4-\nLooking at the relative sensitivity in this way we see that the Lind instrument\nwill detect 3.1 microcuries, but this result is based upon the assumption that all\nthe emanation generated is continually expired. In practice probably not more\nthan 1/8 that forms is expired. on the basis of actual practice then about 25\nmicrograms of Ra. must be present in the living person to detect it positively by\nthe emanation method as against 10 micrograms Ra, the amount detectable by the\ngamma ray machine.\nThese deductions when verified by experiment will make it evident\nthat the emanantion in the expired air of a person containing radium in amounts\nup to 10 or 20 micrograms must be concentrated before it can be detected and\nestimated quantitatively by the emanantion method. We recommend that 100 to\n200 liters of expired air be first dried and then passed thru a U-tube immersed\nin liquid air to condense the emanation. The emanation thus separated may then\nbe determined quantitatively by drawing it into a calibrated electroscope.\nA blank experiment should be run by way of control."
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