On the Record: Beckman Model G 
pH Meter

Beckman Model G pH Meter

Courtesy of Danaher. Photo by Gregory Tobias.

When it came to the measurement of acidity and alkalinity, the Beckman Model G pH meter was the go-to instrument for many labs in the decades surrounding 1950. Thanks to a variety of electrodes, this meter could be adapted to measure pH levels in everything from blood to soil. It’s no wonder we have several of these instruments in our collection. What we hope to collect from you are stories that describe it in action. Have you used a Model G or a similar pH meter? Will you share your story with us?

Please fill out the form below or e-mail your story to ontherecord@chemheritage.org.


Model G Tales from the CHF Oral Histories and Archives

Arnold O. Beckman, from His Oral History

Now at about the time we came out with our pH meter, there was a very disturbing publication, I think by a professor at Stanford University, saying that a glass electrode really measures the depth of immersion rather than pH. They made an electrode out of a length of 015 tubing and they found that it got different pH readings depending on how deeply it was immersed in the liquid. That was devastating to us; we finally looked into it and found out that sure enough, it was true. What we didn’t realize was that there was a leakage path over the outside of the electrode and down inside. The higher your electrode rod, the shorter this leakage path. That’s when we started to overcome that. The surface resistivity of Corning 015 glass is pretty low. We started coating it with shellac and with resins of various kinds and with picein wax and all we’d melt on that. Finally, we decided these are just temporary, unsuitable things. The only way was to get rid of that interface. That led to our patent on the sealed electrode. That was the thing that really gave us a stranglehold on the glass electrode business.

Of course there’s been a constant change in our instruments. From the days of the original pH meter and the spectophotometer, the microchip has come in. So all of our instruments had to be redesigned and we have a whole flow of new instruments. Now that’s an in-house development. We have the techniques and we know what to do. We depend on an outside supplier. We design our own chips, for example, but we have them made by others for us. We don’t do that. But we have all that capability.

We had a one-man sales force. We didn’t have any capital. We didn’t have the financial resources to build up our own sales force, so we sold through the dealers. I recall our final total was twenty-eight dealers. The principal one was right here in Philadelphia, Arthur H. Thomas Co. Ed Patterson at Arthur H. Thomas encouraged me to go ahead and build the pH meter; he was the one who came up with the high figure of 600 pH meters that might be sold in ten years. When we came up with the spectrophotometer, Arthur H. Thomas, Eimer & Amend in New York (that was before it was acquired by Fisher), Central Scientific in Chicago, E. H. Sargent in Chicago, were dealers. They all bought one of these things and sold it. So that was the way the word got out. Once we got a few of them out, papers began to appear and talks were presented at scientific meetings.

Masao Horiba, from His Oral History

Masao Horiba

And when I looked into it, I found that all the Japanese companies and research institutes were using Beckman pH meters. I bought one of Beckman’s pH meters for the equivalent of six months of my salary. And thanks to this, during those six months, I lost about 3 kilograms of weight! [laughter] I inspected Beckman’s pH meter closely and compared their meter with our own. Although our pH meter had not been commercialized yet, I thought that our pH meter could compete well with the Beckman.

Japan needed good agrichemicals—fertilizers, for instance—to increase rice production. At that time, ammonium sulfate was the most efficient fertilizer for rice production. Even the Japanese government tried to persuade businesses to increase the production of ammonium sulfate. To create ammonium sulfate you need to mix sulfuric acid in ammonia, a process during which pH control is critical. Therefore, the sales of our pH meter increased dramatically because it was accurate and worked very well in humid environments.

James F. Feeman, from the CHF Archives

Use of Beckman’s Model G pH Meter by the Althouse Chemical Company and Althouse Chemical Division, Crompton & Knowles Corporation

During the 1940s, although I was a chemistry student at three outstanding institutions of higher learning, I cannot remember having seen, much less used, the novel Beckman Model G pH meter. If those institutions had any in their chemistry laboratories, they were not readily accessible. I did, however, receive rigorous academic training in analytical and electrochemistry. Arnold O. Beckman had invented the Model G in 1934. His company sold 444 in 1936, the first year of production. Many of those instruments presumably went to industrial firms that had a need for them and could justify their purchase.

When I joined Althouse Chemical Company in August 1950, their chemists and engineers were using Model Gs on a daily basis in their laboratories and plant in Reading, PA. I don’t know when their first pH meters were acquired, but one was pictured in a 1946 advertisement to the trade. pH controls were already incorporated into plant processes. The Model G was, indeed, very important to maintenance of the quality and quantity of their production.

Althouse’s production was mainly of azo dyes for textiles, which were, by definition, colored substances. Indicators and indicator papers were in common use in academic laboratories for acid-base titrations and other analytical procedures. Obviously those aids had only limited use for following reactions and analyzing colored dye solutions.

Dye chemists were very ingenious in the use of rudimentary paper chromatography and spot tests to follow the course of a reaction. One valuable technique consisted in forming a small pile of salt (NaCl) on a piece of filter paper, placing a drop or two of dye solution on the pile and performing tests on the outrun from the pile, which was often colorless but could show the presence of an intermediate. The filter paper could be replaced by an indicator paper for rapid determination of approximate pH. In doubtful cases a comparison could be made to a similar run-out on a blank piece of filter paper. Congo Red (for low pH) and Brilliant Yellow or Thiazole Yellow (for higher pH) were commonly used.

The Model G meters at Althouse were placed on mobile carts so they could be readily moved about the laboratory or plant. The carts were designed and built in the company shop. Their tops were the same height as the laboratory workbenches. They featured a storage cabinet below the top where extra electrodes, tissues, and buffer solutions were kept. An upright steel rod was fastened to the top adjacent to the meter. Electrodes were not kept in the compartment designed for them. The electrodes were held in a dual clamp, which could easily be attached to, or detached from, the fixed rod. The electrodes were stored suspended in distilled water or 0.1 N hydrochloric acid in a small beaker and were rinsed with water before use with a wash bottle, the water being guided into a funnel inset into the top of the cart and leading to a receptacle in the cabinet. 

In the semiworks or manufacturing plant, samples were usually removed from the reaction tubs and taken to the nearby pH meter to check pH. Adjustment was made and further samples were taken and checked as needed.

In the laboratory a similar procedure was sometimes followed, but more often the electrode pair was fastened to a ring stand and the tips immersed directly into the reaction solution or slurry. This allowed continuous monitoring of pH and adjustment as needed to maintain a certain pH. This configuration was very advantageous when an azo coupling reaction was being carried out in an open beaker or larger container with mechanical stirring. Care had to be taken to protect the glass electrode, which was fragile and easily cracked on impact with a hard object. When single electrodes became available, monitoring could also be done through one neck of a multinecked flask.

Standard buffers (pH 4, 7, or 10) were used frequently to assure accuracy. The most accurate readings were attainable when the instrument was standardized at the same temperature and at a pH close to that of the reaction. In more alkaline solutions, or solutions containing high concentrations of sodium ions, the observed values of pH were too small and had to be corrected using nomographs. The error at a given pH increases with increasing amounts of sodium ion; for normal electrodes the error is so great that even with corrections an accurate pH cannot be obtained. But normal glass is useful at pH 0 to 11. Later, special glasses were developed to minimize sodium error. And these glasses also provided -5 to 100 degrees temperature range. Over the years we used a variety of electrodes including Calomel reference electrodes, but eventually standardized on Beckman’s Futura Glass low sodium error electrode and Beckman’s Futura Reference electrode filled with KCl and AgCl solution.

Unfortunately when our plant and laboratories at Gibraltar, PA, were inundated by the flooding Schuylkill River in June 1972, many of the Model Gs were underwater. We then decided to replace them with pH meters that were more advanced in design and much smaller.

Robert J. Manning, from His Oral History

I don’t know. You couldn’t patent the idea of ultraviolet spectroscopy. Using a quartz prism was something that was known. Other people had used those instruments, and there were a lot of different designs and so forth using a quartz prism. You’ve got one sitting in the museum, a DU that’s using a Model G pH meter as the readout. The monochromator was developed, but they had to have some way to measure the signal, so they used the Model G pH meter. Later on, the DU had its own electronics, which consisted of the pH meter electronics stuck in the DU box.

Emil L. Smith, from His Oral History

Beckman’s pH meter came along around about 1938 or 1939. I had a glass electrode assembly that I was working with to measure the pH in my buffers back in 1935 and 1936. You couldn’t use a hydrogen electrode with carbonate-bicarbonate buffers, which I needed to do photosynthesis. If you put in enough hydrogen, you expelled all the CO2, and you no longer had a buffer. (It’s bringing back memories.) 



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