February 8, 1941
Dr. T.K. Sherwood
National Defense Research Committee
1530 P Street NW.
Dear Dr. Sherwood:
If you desire us to make one or more instruments for oxygen analysis, as mentioned in your letter of January 25 an dour
subsequent telegrams, I would like to have specifications, especially with respect to the following points. I think that we
could provide an instrument satisfying almost any particular specifications, provided that some leeway were granted in other
1. Should the range of oxygen partial pressure be 0 to 160 mm. or 0 to 200 or still larger?
2. Do you want measurements made on the air of the room, or measurements made on small gas samples, which would be
introduced into a chamber in the apparatus by displacement of the gas already there? We could make the apparatus with a volume
to be displaced by the gas as small as about 10 cc.
3. Is it all right to require that the instrument be level during the measurement?
4. Are there any restrictions on weight or volume? The instrument would weigh perhaps three pounds and be six inches
in largest dimension, but it could be made lighter and smaller.
5. Will there by much variation in total pressure? If all measurements are made at atmospheric pressure we would
not worry about adjusting the instrument to be independent of variations in total pressure.
6. Would +/- 3mm. partial pressure of oxygen be satisfactory rather than +/- 3% accuracy?
7. Should the instrument be adjusted to be an independent of temperature variations, or would it be satisfactory
if it read correctly at room temperature?
8. Is a relaxation time of 10 seconds satisfactory?
9. I should point out that nitric oxide, nitrogen dioxide, and chlorine dioxide would cause errors, each millimeter
of one of these gases corresponding to about 1.2 mm. of oxygen pressure.
Very truly yours,