pH meter

In October 1934, Arnold Beckman filed his patent for the "acidimeter"—later renamed the pH meter—but the invention wasn't his idea. It was the citrus industry's problem that wouldn't go away.

Dr. Glenn Joseph, a chemist at the California Fruit Growers Exchange (later Sunkist), faced an impossible measurement task. Lemon juice extract acidity determined product quality, but litmus paper—the standard method—was worthless because processors added sulfur dioxide as a preservative, which bleached out the litmus completely. Glass electrodes for pH measurement existed—Max Cremer had discovered the principle in 1906, Fritz Haber refined it by 1909—but they were fragile and produced signals far too weak to measure directly.

Beckman's solution required three independent technology streams to intersect. First, the glass electrode itself—Cremer's 1906 discovery that thin glass membranes develop electrical potential proportional to hydrogen ion concentration. Second, vacuum tube amplification—Lee De Forest's 1906 Audion triode had created electronic amplifiers, and by the early 1930s indirectly heated cathode tubes enabled reliable, manufacturable amplification. Third, the economic pressure of California's citrus boom—the Southern California Fruit Exchange formed in 1893, and by the 1930s California's two most famous exports were films and citrus.

Beckman possessed the rare convergent skillset: expertise in glassblowing, electrical engineering, and chemistry. He suggested placing the glass electrode in a vacuum-tube amplifier's grid circuit, producing an amplified signal readable by an electronic meter.

In 1935, Beckman set up a small shop in Pasadena with students from his laboratory. The Model G pH meter, produced from 1935 to 1950, was priced around $195. The invention kicked off rapid development of the entire electronic scientific instrument industry. In 1941, Beckman introduced the DU spectrophotometer. National Technical Laboratories renamed itself Beckman Instruments in 1950. The company merged with Coulter Corporation in 1997 to form Beckman Coulter, acquired by Danaher Corporation in 2011 for $6.8 billion.

In 1998, readers of Chemical and Engineering News voted Beckman one of the most influential chemists of the 20th century—not for discovering anything new, but for making precision measurement cheap and reliable enough that thousands of other scientists could discover things themselves.