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    "label": "Report, 1926",
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    "title": "Report, 1926",
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        "Safety Light Collection",
        "Records Related to Radium Dial Painters"
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    "ocrText": "-20-\nIn considering the effect of Mesothorium and radium we must bear in\nmind certain facts. Mesothorium decays 250 times as fast as radium does, and\nconsequently in its pure state, weight for weight, its activity would greatly\nexceed that of radium. But in these paints the quantity of mesothorium is\nnot expressed in milligrans by weight but by its equivalent in radium. Thorefore\nthe activit of the two compounds compared bear the same ratio as the values\nassigned to the preparations.\nAlthough mesothorium gives off no rays, its first decomposition product\naftor mesothoriun has boen separated gives off powerful beta and gamma rays.\nFor this reason the operator must protect himsolf against these rays. On the\nother hand in thepproduction of radium, the product giving the penetrating\ngamma rays (RaC) is formed rather slowly.\nIn studying the possible effect of mesothorium that may become deposit ted\nin the body one must bear in mind the faot that the half period of radium is'\n1580 years while that of mesothorium is 6.7 years. In the decay of radiun we\nfirst have an emanation having a half period of 3.8 days. This is followed by\nthe active deposit of rapid change (RaA, RaB, RaO) followed by an act ive deposit\nof slow change RaD, Rak, Rap. Radium D and E emit soft beta rays and have a half\nperiod of 16.5 years and 4.85 days respectively. Radium F or polonium emi ts\nalpha rays and has a half pertod of 136.5 days. But in the case of mesothorium\nthe emanations have a half period of only 54.5 seconds, which is followed by\nthorium A, B, and 0 which are comparable to the sama series of radium. Thorium\n0 is followed by Thorium D (Th lead) which is stable. Among the thorium decom-\nposition products we do not haveone similar to radon of the radium products\nwhich has a comparatively long live emitting alpha radiat lons. The maxium range\nof alpha particle from the thoritum series is 8.6, while for the rad ium series\nit is 6.94 ame\nAt the meeting of the Association for the Advan cement of Soience in December"
}