Arnold Beckman (Born 10 April 1900): American inventor of scientific instruments who invented the first pH meter in 1934 to assist a former classmate working at a citrus processing plant to measure the acidity levels of lemon juice. This invention, which was initially known as an “acidometer” and patented in October 1934, led to the founding of Beckman Instruments, now known as Beckman Coulter. Beckman earned a total of 14 patents for various scientific instruments during his career. The Arnold and Mabel Beckman Foundation has now donated over $300 to support science education programs, with his scientific and philanthropic achievements being honoured by the US National Medal of Technology and National Medal of Science (see Arnold Beckman | Lemelson (mit.edu), Beckman pH Meter – National Historic Chemical Landmark – American Chemical Society (acs.org) and Arnold O. Beckman | Science History Institute).
Kai Manne Börje Siegbahn: Born 20 April 1918): Swedish physicist who shared the 1981 Nobel Prize in Physics for his work on the development of high-resolution electron spectroscopy (note that his father, Manne Siegbahn, won the same prize nearly 60 years earlier in 1924). His highly accurate measurements on the binding energies of atomic electrons, coupled with the dependency of those binding energies on the chemical environment of the atoms, led to the development of electron spectroscopy for chemical analysis (ESCA) (see April 20 – Today in Science History – Scientists born on April 20th, died, and events , Kai Manne Börje Siegbahn: Physics Today: Vol 60, No 11 (scitation.org) and Kai Siegbahn – Wikipedia).
Louis-Marie Hilaire Bernigaud de Grange: (Born 1 May 1839): French industrialist and engineer from Besançon who invented artificial silk. His accidental discovery of nitrocellulose as a possible replacement for silk was made in the late 1870s, while working with Louis Pasteur on a solution to an epidemic that was impacting adversely on the French silkworm industry. Unfortunately, his “Chardonnett silk” proved to be highly flammable and was ultimately replaced with more stable fibres (see Hilaire de Chardonnet – Wikipedia, Hilaire de Chardonnet Google Arts & Culture and Hilaire Chardonnet (May 1, 1839 — March 11, 1924), France chemist, engineer, Industrialist, scientist | World Biographical Encyclopedia (prabook.com)).