Usage: Used to determine the pH (hydrogen ion concentration) of solutions. The glass electrode pH meter was developed by A. O. Beckman in 1935. This specimen is essentially identical to the first commercial pH meters Beckman made in the 1930’s. Thus the only evident differences between the current specimen when the instrument was first offered and described in the 1936 Eimer & Amend catalog is that the meter is square instead of round and a screw is replaced with a knob for the zero adjust as seen in the photograph of the instrument's control panel. The miniature electrodes shown in the close-up photograph of the electrode compartment, are the standard set provided with this instrument, again very similar to the original electrodes provided in 1936, but redesigned for improved performance in 1937. Additional photographs of the instrument are available here: 1) closed up for transport and 2) open for operations.
Description: The walnut veneer case is 11¼”x 8¼”x 10”h. See the detailed description in the Eimer & Amend catalog pages 435-6 available as a pdf here. The only apparent differences in the instrument from this description is the replacement of a round meter face with a square model and a screw with a knob for the “Zero Adjuster.” There is a brass name plate placed below the name “BECKMAN pH METER on the control panel, inscribed: “Braun-Knecht-Heimann-Co. / San Francisco.” A 7” x 10” card providing a brief description of operation and maintenance (“Instructions for Beckman pH Meter Model G”) is held in the inside of the lid by four white thumb-tacks. There were no batteries included with the instrument.
A manual—Bulletin 299, Instruction Manual , Beckman Model G Laboratory pH Meter—was folded-up in the lid compartment of the instrument. It is dated November 1954 on the back cover
© R. Paselk