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June 11th, 1929.
Dr. James E. Ives,
Room 1-123 "C" Bldg.,
16 Seventh St. S.W.
Washington, D. C.
Dear Dr. Ives:
The matter of determining the quantity of radium in unknown
preparations by the film method may be accomplished with a fair degree of
accuracy, provided the physical conditions are well standardized and, held
within certain limits. However, my experience has been that it is
difficult to prepare a standard which will serve satisfactorily for measur-
ing unknown preparations unless such preparations are preparal in a manner
identical with that utilized in preparing a standard.
At one time in the refining of radium we used so separate a
product which we termed "slimes", such products being a concentration of
radium in the fines of the ore and, one would assume that these products
could be compared successfully by the film method, but such was not the
case - by attempting such a practice we often had variations of 100% or
more. If you elect to follow this course, I would suggest that you
have at least one of your samples so collected, analysed so that you actu-
ally know the radium content and then use such a preparations as a standard.
The amount of material placed in the electroscope for measure-
ment must be the same and, the physical conditions identical. Any varia-
tion in the amount of material, the distance from the electrode, the physical
characteristics of the incinerated residue, etc., will obviously introduce
errors.
It is difficult for me to advise you definitely on such a
subject, as this, for after all one can arrive at definite conclusions based
upon experimental data only. I would consider it rather hazardous to
prepare a preparation containing a known amount of radium and use that as a
standard for computing the quantities of radium in unknown preparations
by the film method. If it is at all possible I would suggest that you
have the preparations collected and analyzed for the radium and mesothorium
content, for after all that is the only sure way of knowing what you have
present. The film method is more or less qualitàBive at the best.
Sincerely yours,
Vice President.
HHBarker:RH
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"ocrText": "June 11th, 1929.\nDr. James E. Ives,\nRoom 1-123 \"C\" Bldg.,\n16 Seventh St. S.W.\nWashington, D. C.\nDear Dr. Ives:\nThe matter of determining the quantity of radium in unknown\npreparations by the film method may be accomplished with a fair degree of\naccuracy, provided the physical conditions are well standardized and, held\nwithin certain limits. However, my experience has been that it is\ndifficult to prepare a standard which will serve satisfactorily for measur-\ning unknown preparations unless such preparations are preparal in a manner\nidentical with that utilized in preparing a standard.\nAt one time in the refining of radium we used so separate a\nproduct which we termed \"slimes\", such products being a concentration of\nradium in the fines of the ore and, one would assume that these products\ncould be compared successfully by the film method, but such was not the\ncase - by attempting such a practice we often had variations of 100% or\nmore. If you elect to follow this course, I would suggest that you\nhave at least one of your samples so collected, analysed so that you actu-\nally know the radium content and then use such a preparations as a standard.\nThe amount of material placed in the electroscope for measure-\nment must be the same and, the physical conditions identical. Any varia-\ntion in the amount of material, the distance from the electrode, the physical\ncharacteristics of the incinerated residue, etc., will obviously introduce\nerrors.\nIt is difficult for me to advise you definitely on such a\nsubject, as this, for after all one can arrive at definite conclusions based\nupon experimental data only. I would consider it rather hazardous to\nprepare a preparation containing a known amount of radium and use that as a\nstandard for computing the quantities of radium in unknown preparations\nby the film method. If it is at all possible I would suggest that you\nhave the preparations collected and analyzed for the radium and mesothorium\ncontent, for after all that is the only sure way of knowing what you have\npresent. The film method is more or less qualitàBive at the best.\nSincerely yours,\nVice President.\nHHBarker:RH"
}