Document ykG6raVnbZX9XODNV8gZ6J6jn

/ UNIVERSITY OF CINCINNATI ENT or PREVENTIVE MEDICINE AND INDUSTRIAL HEALTH COLIEOI or NIDIONI--IDIN AVENUE CINCINNATI I*. ONIO CAOLI ADDUCE*: KETLAS. CINCINNATI TELEPHONE: CAMTOi Ul4 September 7, 1956 AIR-MAIL Mr. Elmer P. Wheeler Industrial Hygienist Monsanto Chemical Co. 1700 S. Second Street St. Louis I), Missouri Dear Elmer: I am enclosing; two letters for your consideration in relation to the concentration-of Aroclor 121+2 in air that is saturated with (Pydraul F-1500 The one letter contains results obtained in three phases of this study whereas the other contains only the results obtained in the latter 2 phases. We believe the results obtained in each successive phase are more nearly exact. We believe that there may have been a slight crack in the Mlllipore filter paper while samples were being obtained during the first phase, thus giving results a little high. This was not the case in the second or third studies. The few samples obtained during the third study are believed better (and to be fairly accurate) than those determined during the second since they were sampled for one hour rather than 15 minutes resulting in a quantity of chloride that was on the center of the analytical curve. We doubt that with the sensitivity of the method and the number of samples taken that a significant distinction can be made between (l)one and two bubblers of Pydraul F-150 for generating the atmosphere and (2)that an Increase in concentration would be obtained by bubbling the air through a third bubbler containing Pydraul F-150. Such statistical distinction could be obtained if sufficient samples were collected.. The number of samples required could be statistically ascertained, however, this would be a rather large number of samples. For example, it would require between 50 and 100 samples to ascertain a statistical difference of one mlorogram per liter on data with deviations like that obtained in the first phase. (Each sample requires two analyses, le, one for each of the two absorption towers collecting the thermally decomposed Aroclor 1242.) Since our deviation has MUNS 090856 Page 2 Mr. Elmer P. Wheeler September 7. 1956 decreased In the second and third phases this figure would probably be reduced a little for data such as we have obtained most recently. Sincerely yours JKT:fk cc: Mr. Wheeler (Washington,D.C.) P.S. I have sent a photo with the original letter to St. Louis; also I have enclosed a photo with the copy of the letter to Washington. Since I am very low on these pictures will you keep one and return the other MONS 090657