Invoice from Arnold O. Beckman to W. E. Baier
for developing and calibrating McLeod gauges and glass electrodes -- components involved in the early Beckman pH meter.
Arnold Beckman invented his first pH meter in 1934…
Directions for calibrating a McLeod gauge for use with the early model of the Beckman pH meter. This letter is likely related to the handwritten McLeod gauge diagrams and calculations also found in this folder. At the…