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 respects.
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,