Charles Casey (left), president of the American Chemical Society, presents a bronze plaque to David Tirrell, chair of the Division of Chemistry and Chemical Engineering, designating the Beckman pH meter a National Historic Chemical Landmark. Invented by Caltech alum, trustee, and former professor of chemistry Arnold O. Beckman, the pH meter—a device for quickly measuring acidity—revolutionized instrumentation and led to his founding Beckman Instruments, a leading manufacturer of equipment used in medicine, industry, and science.