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UNIVERSITY OF MINNESOTA
SCHOOL OF CHEMISTRY
MINNEAPOLIS
April 9, 1931
OFFICE OF THE DEAN
Mr. Howard H. Barker
Vice President of the
United States Radium Corporation
APR 11 1931
535 Pearl Street
New York City
Dear Barker:
Dr. Paul D. Berrisford, 810 Lowry Building, St. Paul, who is
also a member of the staff of our University Hospital, called today
to get information about radium paint and I have referred him to you.
His problem is the following.
He wants to do some experimentation toward devising an instru-
ment for testing the sensitivity of the human eye to weak light sources.
He would like to make up discs, possibly of different sizes, and to
time the eyes of different individuals in adjusting the sensitivity so
that the source just becomes visible in the dark.
I have warned him that the luminosity of radium paint does not
remain constant. He would like, to have a paint that would become visible
the subject
in about two minutes in changing from ordinary room conditions to complete
darkness. I have told him that the weaker the paint, the slower its rate
of decay and that a paint after application with a binder has a slower
rate than the dry paint. I have suggested that possibly an aged paint
which has reached its nearly light minimum might be most useful to him.
I suggested that he should inquire whether you could make up such
dials for him and give him the luminosity in lamberts and any information
about the rate of decay that you might have.
I am not sure whether his method is feasible at all. Possibly, you
have already considered this proposition and can advise him. I think that
if he succeeds in getting a satisfactory device, he would make them up in
fairly large quantities through some medical supply house in St. Paul for
distribution to the profession.
With best regards,
Very sincerely yours,
S. L. Lind
S. C. Lind,
Director.
scl:en
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"ocrText": "UNIVERSITY OF MINNESOTA\nSCHOOL OF CHEMISTRY\nMINNEAPOLIS\nApril 9, 1931\nOFFICE OF THE DEAN\nMr. Howard H. Barker\nVice President of the\nUnited States Radium Corporation\nAPR 11 1931\n535 Pearl Street\nNew York City\nDear Barker:\nDr. Paul D. Berrisford, 810 Lowry Building, St. Paul, who is\nalso a member of the staff of our University Hospital, called today\nto get information about radium paint and I have referred him to you.\nHis problem is the following.\nHe wants to do some experimentation toward devising an instru-\nment for testing the sensitivity of the human eye to weak light sources.\nHe would like to make up discs, possibly of different sizes, and to\ntime the eyes of different individuals in adjusting the sensitivity so\nthat the source just becomes visible in the dark.\nI have warned him that the luminosity of radium paint does not\nremain constant. He would like, to have a paint that would become visible\nthe subject\nin about two minutes in changing from ordinary room conditions to complete\ndarkness. I have told him that the weaker the paint, the slower its rate\nof decay and that a paint after application with a binder has a slower\nrate than the dry paint. I have suggested that possibly an aged paint\nwhich has reached its nearly light minimum might be most useful to him.\nI suggested that he should inquire whether you could make up such\ndials for him and give him the luminosity in lamberts and any information\nabout the rate of decay that you might have.\nI am not sure whether his method is feasible at all. Possibly, you\nhave already considered this proposition and can advise him. I think that\nif he succeeds in getting a satisfactory device, he would make them up in\nfairly large quantities through some medical supply house in St. Paul for\ndistribution to the profession.\nWith best regards,\nVery sincerely yours,\nS. L. Lind\nS. C. Lind,\nDirector.\nscl:en"
}