Patenting the Pauling Oxygen Meter

Series of diagrams of the Pauling Oxygen Meter. June 8, 1942.

The story of how Linus Pauling’s Oxygen Meter came into being has already been well documented on this blog.  In our previous discussion we outlined the workings of the oxygen meter itself, the improvements that were made, and the fate of the invention in the aftermath of World War II. Today’s post will add to that story by focusing on the uniqueness of Pauling’s invention and the means by which the Oxygen Meter came to be patented.

On October 7, 1940, a contract was drawn up between Caltech and the National Defense Research Committee (NDRC) for the development of the instrument. In a letter addressed to the NDRC, Pauling stated that, in view of the circumstances, and because his desire was to be of service to the country, he was willing to grant the government a non-exclusive, royalty-free license covering the entire invention throughout “the period of national emergency,” referring to World War II. He also expressed his desire that the National Defense Research Committee decide who would be given the rights to the apparatus at the end of the war.

Pauling wanted to file an application for a patent on his invention “inasmuch as it seems it will be of use in various fields other than that of national defense” – a correct supposition as it turned out. At the end of the letter, he commented that he wished to “proceed with the greatest speed in developing the instrument to the point of maximum usefulness in national defense.”

Irvin Stewart, secretary of the NDRC, wrote back and essentially told Pauling that, according to the patent clause, because he had created the invention after signing a contract with the Committee, the government was entitled to a royalty free license on the invention not only during the war, but throughout the life of the patent.

In a letter to Dr. James B. Conant of the NDRC, written February 15, 1941, Pauling next expressed a desire to patent the fundamental idea of his oxygen meter, “now that my oxygen meter will soon be put in use in other laboratories,” rather than the actual device itself. He mentioned the contract agreed to by the NDRC and Caltech, which stated that the Committee would have the sole power to determine whether or not a patent application should be filed. He also noted that “there are many uses to which the instrument might be adapted other than the original one.”

Pauling received an answer from Irvin Stewart on March 28, 1941, in which Stewart advised Pauling to apply for a patent on all of his developments that antedated the contract between the Committee and Caltech. Pauling replied that it was only after attending a meeting of the National Defense Committee in Washington, D.C. on October 3, 1940, that he initially learned of the need for an oxygen meter, and it was from this meeting that his ideas stemmed.  Pauling’s desire to patent his idea was running into roadblocks, but the uniqueness of what he had devised could not be denied.


The Pauling Oxygen Meter. approx. 1940.

Pauling’s “Apparatus for determining partial pressure of oxygen in a mixture of gases” was unique for many reasons. For starters, it was both light-weight and tough. It also made use of the fact that oxygen is a strongly paramagnetic gas, which means that its magnetism does not become apparent until it is in the presence of an externally applied magnetic field. Only a few gases other than oxygen are paramagnetic, but they are less susceptible to magnetism than is oxygen. For this reason, the apparatus was valuable in determining the oxygen content of a mixture of gases, except where other paramagnetic gases such as nitric oxide, nitrogen dioxide, and chlorine dioxide were present.

Because Pauling’s device was going to be used in war, the government wanted to limit the number of people who knew of its existence. The NDRC eventually granted permission for Pauling to reveal the nature of his invention to his patent attorney in Los Angeles, provided that he did not disclose the nature of the invention to anyone else. When Mr. Richard Lyon, of Lyon and Lyon, Attorneys, requested information on the assembly of Pauling’s invention in order to better research existing inventions like it, Pauling asked Dr. Reuben E. Wood, who worked on the device with Pauling, to fill in the attorney. It is from this exchange that we learn a bit more about what made the device special.

Wood told Lyons that Pauling’s device was novel in many ways. For one, Wood could not find any other reference to the use of the magnetic susceptibility of oxygen as a means of analyzing a mixture for it.  Also unique to the Pauling method were the facts that the composition of the gas sample was not altered by analysis, and that “the moving part of the device is actuated directly by the presence of the gas in the analyzing chamber.”

A similar apparatus, designed by Glenn G. Havens, had a recovery time of three minutes after being jarred or after a gas sample reading before it could be used again, while Pauling’s only needed one second. Another major difference between the two devices was that Pauling’s was portable while Havens’ was immobile and fragile.

Furthermore, Pauling’s model utilized a permanent magnet instead of an electromagnet, which meant that his magnet weighed less. Also, no source of electricity was required for the instrument to work except that required to operate a light bulb, which could be powered using a flashlight cell. All in all, Pauling’s model was more efficient, portable and dynamic than any competing instrument. Wood believed that all of these unique attributes were patentable.

Pauling filed a patent application on August 23, 1941. Having done so, he was promptly informed by the Department of Commerce of the United States Patent Office that the contents of his application “might be detrimental to the public safety of defense,” and was warned by the government to “in nowise publish or disclose the invention or any hitherto unpublished details of the disclosure of said application, but to keep the same secret.”

Later, Pauling discussed with the Office of Scientific Research and Development the procedure for obtaining a suitable manufacturer to produce his invention. The parties involved ultimately decided on Dr. Arnold O. Beckman and his organization as the likely purveyors, as they were familiar with instrument production problems through their experience in manufacturing parts for this and other technical equipment for laboratory use.

Reuben E. Wood. March 1948.

Dr. Wood, who had worked on the oxygen meter with Pauling, was also interested in patenting certain features which he had developed, so he wrote to the NDRC for permission to apply for a patent in March 1942. Important aspects which he improved upon were a “method of balancing the test body;” an improvement “which reduces the effect of temperature changes in the indication of the meter;” and “a method of selecting range of maximum sensitivity.” He later wrote to Richard Lyon enclosing four Records of Invention statements detailing his improvements on the Pauling Oxygen Meter.

However, in a letter to Captain Robert A. Lavender of the Office of Scientific Research and Development, Pauling communicated that it was not the intention of the California Institute Research Foundation to apply for patents on the inventions of Dr. J. H. Sturdivant and Dr. Reuben E. Wood. As concerned the Oxygen Meter patent, Wood was left out in the cold.


In March 1944 the Naval Research Laboratory of Washington, D.C., sent a confidential statement to the Chief of the Bureau of Ships in which it was stated that

this Laboratory has been interested in the development of an oxygen indicator suitable for service on submarines. The most satisfactory instrument has appeared to be the Pauling Oxygen Meter and a detailed study has been made of its operating characteristics, ruggedness, dependability and general efficiency with very promising results.

The letter also noted that the Pauling Oxygen Meter was found to be superior to a similar instrument – namely, the one created by Havens.  The efficacy of Pauling’s invention was becoming manifest.  As he himself had predicted, the device would be of use for both the war effort and in peace time.

Finally, after much brainstorming and years of collaboration, hard work and improvement, and after having been proven exceedingly useful during World War II, Pauling’s Oxygen Meter was patented on February 25, 1947, some five and a half years after the initial application was submitted.

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The Oxygen Meter

The Pauling Oxygen Meter. approx. 1940.

Have most promising method determination partial pressure oxygen. Best available post-doctorate assistant offered job elsewhere. May I hold him. Please telegram or telephone.

-Telegram from Linus Pauling to James B. Conant, October 8, 1940

On October 3, 1940, Pauling met with his colleague, W.K. Lewis, in New York City. At this meeting Lewis informed Pauling that the military needed an instrument capable of measuring the pressure of oxygen in a mix of gases. He explained that soldiers operating in low-oxygen environments – primarily airplanes and submarines – were sometimes affected by loss of consciousness and even death due to unchecked oxygen depletion. An oxygen meter would enable pilots and submariners to track oxygen levels within the cabin, allowing them to adjust for dangerous decreases.

The following day, Pauling began mentally sketching out plans for the instrument and before long he had struck on a possible design. On October 8, he sent a telegram to National Defense Research Committee (NDRC) administrator James Conant stating that he had a “most promising” means of determining the partial pressure of oxygen. Soon after, Pauling received an unofficial order from Harris M. Chadwell, Conant’s right hand man, to begin experimenting with the design. After another exchange of letters, Pauling was appointed “official investigator” for the project and given a budget which funded Pauling and his colleague Reuben Wood, a temporary assistant, with materials and equipment for a six-month probationary period.

Torsion balance used in the Pauling oxygen meter. approx. 1945.

The apparatus was based on the principle of a torsion balance, a measuring device originally developed by Charles-Augustin de Coulomb in 1777. Wood created the balance by connecting a tiny metal bar to a quartz fiber. He then attached a hollow glass sphere to each end of the bar and a mirror to the fiber crossbar. The entire device was then strung between the points of a standard horseshoe magnet and shielded by a bell jar. When the spheres were filled with air, the paramagnetic forces present in oxygen atoms would cause the dumbbell setup to rotate, twisting the quartz fiber. The mirror on the fiber, as it twisted, would alter the angle of a reflected light beam, striking a photocell. The photocell readings would then register on a dial, in the process giving an approximate measure of present oxygen levels.

By November 1, less than a month after receiving the assignment, Pauling and Wood had constructed and tested a model. Though fragile and prone to decalibration, it worked.

After presenting his and Wood’s work to government officials, Pauling was told that the meter would need to be usable despite frequent acceleration and deceleration, tilting on all axes, and constant shock and vibration. In response, the duo designed an adjustable support for the apparatus which allowed it to remain stable despite movement and shock. Shielding and damping techniques were developed too, allowing the meter to give accurate readings under moderate strain from outside forces.

There were, of course, setbacks. The quartz fibers were nearly invisible and required special tools to create and place. The glass bubbles used on the instrument had to be hand-blown but were so delicate that it took many tries – sometimes hundreds – to create a single perfect bulb. Supplies, too, were difficult to acquire. Liquids for damping, metals, and magnets all proved hard to find, further slowing the research process.

Though development was cumbersome and sometimes frustrating, it was clear by the summer of 1941 that Pauling’s oxygen meter was a success. The NDRC, pleased with Pauling’s work, renewed his contract, requesting that five additional meters be manufactured and distributed according to committee orders. Despite the production demands placed on his team, Pauling insisted that the design be further improved. Wood suggested a prototype using two magnets rather than one – a new approach which allowed for a sturdier, more accurate model.

Reuben E. Wood. March 1948.

Despite the creation of the Office of Scientific Research and Development, an entirely new war research agency, and major changes in hierarchy and administrative procedure, Pauling’s group worked for seven months manufacturing oxygen meters with little interference from officials. By early 1942, it was clear that his team could not keep up with growing demand for the device.

In response, Pauling turned to Caltech staff member Dr. Arnold O. Beckman, a skilled instrument-maker who, after a meeting with Pauling, accepted a contract with Caltech for the manufacture and distribution of the oxygen meter. To simplify the production process, Beckman built the world’s smallest glass-blowing device for purposes of creating the meter’s bulbs. Through this and a few other innovations, Beckman increased his manufacturing capacity to nearly one-hundred units monthly – at least ten times what Pauling’s team could have hoped to achieve.

For the remainder of the war, Pauling continued to oversee the production and distribution of the oxygen meter and Beckman, with his refined manufacturing process, succeeded in equipping Allied forces with hundreds of the devices. Customized models were also provided to laboratories and government institutions in both the U.S. and abroad, and were instrumental in the development of life-support systems for both pilots and submariners.

The use of Pauling’s oxygen meter did not end with the war. Following the close of hostilities, the meter was repurposed for the incubators used to house and protect premature infants. Hospital staffs were now able to maintain safe oxygen levels, reducing the risk of brain damage and death among newborns. Pauling was proud of his instrument’s peacetime applications and occasionally noted it as one of his more significant accomplishments.