Letters Received to H.H. Barker, September 23, 1928

UNIVERSITY OF MISSOURI RECEIVED COLUMBIA SEP 27 1928 DEPARTMENT OF CHEMISTRY September 23, 1928 Tis If en Mr. H. H. Barker United States Radium Corporation 535 Pearl Street New York City My dear Howard: Your letter and check covering balance of expense account have just come to hand. I shall deposit check on Monday. This additionto my bank balance may help to keep my standing with the bank at par. A minimum cash balance of $100.00 is now required by our looal banks. Being interested in the quantitative aspect of our radium problem, I am pleased to get your data on the radium content of excreta in the Dunn case. Let us examine these data and make a few computations with a view of getting some idea as to the probable sensitiveness of this method for de- tecting radium in living persons. Altho the average of the figures gives a total daily elimination of radium by Miss Dunn of more than 0.010 micrograms, let us take 0.010 micrograms (10 x 10-9 g) in our computations for just at present we are merely concerned with the order of magnitude and not exact fi- gures. If we assume that the dry weight of the entire sample excreta had been used in making the radium determinations--an a 5 gram sample can be handled without introducing experimental difficulties- it is seen that the emanation from it will produce a drift of the leaf of a Lind electroscope of about 1 div. per sec. since the constant of the instrument lies very close to 10 X 10-9 grams radium per div. per sec. Since the radium content of Miss Dunn turne d out to be about 100 micrograms, it follows that per microgram of radium the radium in dai ly excreta would produce a drift of about 0.01 div. per sec. an amount well within the range of detection by the emanation method. On this basis, the daily excreta from a subject containing about 5 micrograms should contain sufficient radium to produce a net drift of about 0.05 div. per sec.- a value fully 20 times the drift observed for a 5 microgram subject when the tests are made by the gamma ray instrument or with the Lind electroscope on expired air. I realize full well that one must not generalize from data based on a single case. One must also expect wide differences in the quanti- ties of radium eliminated by different subjects or the same subject at differ- ent times; nevertheless, this computation seems to indicate that the determi- nation of radium in excreta by the emanation method may turn out to be fully as delicate and positive as any of the other methods on which we have worked so faithfully. Is not our objective to find ways and means of detecting radium in living persons? It is largely on this basis that I proposed that we proceed to make at least a few random determinations of radium with you as subject.