Glenn Joseph writes to Dr. Beckman about the process of finding the right buffer to use in the new glass electrodes inside the pH meter. The identify of the "Dr. Dupont" referenced in this letter is uncertain.

Arnold Beckman invented his first pH meter in 1934 at the request of a chemist from the California citrus industry, who needed an accurate way to measure the acidity of his product. The resulting instrument kicked off rapid development not only of Beckman Instruments, Inc. but also of the electronic scientific instrument industry.