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    "localId": "75721444",
    "label": "Letters Sent to C.H. Granger, June 3, 1927",
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    "title": "Letters Sent to C.H. Granger, June 3, 1927",
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        "Safety Light Collection",
        "Records Related to Radium Dial Painters"
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    "seq": 3,
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    "ocrText": "June 3rd,1927.\nMr. C. H. Granger, Supt.,\nWaterbury Clock Company,\nWaterbury, Conn.\nDear Mr. Granger:\nPlease accept our thanks for your letter of June 1st.\nWe know there has been a great deal of discussion over\nthe relative properties of radium and mesothorium, and the Doctor in\nWaterbury who pronounced himself so strongly on the question of radium\nnot being poisonous and blaming any possible injuries on mesothorium is\nprobably not speaking from a scientific knowledge which he has, but from\nmore or less hearsay. Now from a physical and chemical standpoint there\nis no difference in the action of these two materials. There may be a\nslight difference in the length of the alpha rays, but radium and meso-\nthorium are isotropic and if once mixed one cannot be separated from the\nother. As a matter of fact the only way you can tell mesothorium from\nradium is by a series of measurements, and this is determined by the\nfact that mesothorium loses its emanating power much more quickly than\nradium. The best of physicists and chemists will verify this statement.\nA great deal of the unfavorable impressions against\nmesothorium is on account of the statement that it is many times more\npowerful than radium. This statement is absolutely true, if you should\ntake any given weight of pure radium salt and compare it with a like\nweight of pure mesothorium salt. The mesothorium is approximately 250\ntimes as active. On account of this great activity it will destroy itself,\n80 to speak, in a period of time 1/250ths of the time that it requires\nradium to destroy itself. Now the joke of the whole matter is - and this\nis what the doctors do not know, that when you refer to a milligram of\nmesothorium, you refer to a quantity which has the same amount of emanating\npower as one milligram of radium. In other words mesothorium is sold and\nused in terms based upon its equivalent activity to a milligram of radium.\nIt would take 250 milligrams of pure mesothorium to weigh as much as one\nmilligram of radium. I perhaps may be a little crude and not scientific\nin trying to explain this to you, but trust that you will at least under-\nstand what I am driving at.\nSince early last fall we have used no radio-activity\nin our luminous material except pure radium. For approximately one year,\nbefore we went to a straight radium basis we used a mixture of mesothorium\nand radium in varying proportions, which would average about 60% mesothorium\n-2-\nto 40% radium. From about 1919 until 1925 our average mixture of the\ntwo substances would run to 90% mesothorium to 10% radium. Previous\nto 1919 we used 100% radium. Now here is another fact which modifies\nthe figures somewhat, and that is - that mesothorium contains from 20 to\n25% radium, so when we speak of a combination of 80% mesothorium and\n20% radium you are actually using approximately 60% mesotherium and 40%\nradium. We have never used any radio-active substances in our luminous\nmaterial except these two, since the other known substances are inefficent\nand too short lived.\nAs regards the application work on the Alden Watches, which we:\nare doing for you - The plant Manager is not available until late this\nafternoon and I shall then check the adhesive, methods of application, etc.,\nand write you when I have this information at hand.\nVery truly yours,\nPresident.\nCBLee:RH"
}