In 1934, Glen Joseph, a chemist at the California Fruit Growers Exchange laboratory, was trying to accurately measure acidity in citrus fruit products. The most common method at the time for testing pH, a measure of acidity or alkalinity of a substance, was to use litmus paper. Litmus paper turns different colors depending on the acidity of a substance. This was of no use to Joseph, however, because the sulfur dioxide used as a preservative in citrus Juice bleaches out the paper.
Joseph tried using glass electrodes, but these were susceptible to breakage and gave a very weak signal. He finally called upon his old classmate Arnold Beckman (1900-2004), then employed as a professor at Caltech, who told Joseph that he needed to use vacuum tubes. Beckman later ended up making the instrument himself.
The instrument worked, so well that Joseph soon ordered another one for his laboratory. Beckman realized he was on to something, and a patent was filed in 1934 for this "acidimeter." The following year, the National Technical Laboratories started selling this acidimeter for $195. Despite its steep cost (especially compared to dirt-cheap litmus paper), the company managed to sell eighty-seven instruments in the first three months of production. In 1939 Beckman left his professorship to run National Technical Laboratories full time, and went on to invent many more important laboratory instruments.
The pH meter was a revolutionary instrument in the science laboratory. It was essentially the first portable, precision instrument that could take accurate measurements immediately and reliably. This left the scientist time to concentrate on their research instead of building complicated equipment to make simple measurements.
