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.