Humboldt State University
Robert A. Paselk Scientific Instrument Museum
Student Analytical Balance
New York N.Y.
Humboldt State College, c. 1948
The analytical balance is the most fundamental tool in the chemists arsenal. It is used to determine the masses of, or in other words the amount of stuff in, objects or samples. The balance is a comparison instrument. It compares standard or known weights placed on the left-hand pan to unknown samples or objects placed on the right-hand pan. The current instrument also has a rider (a 5 mg bent wire weight which is moved along the graduated scale on the top of the beam) to measure small (0-5 mg) differences in mass. The short chain suspended between the beam and the screw adjustment in the case is used to zero the beam. The glass case is to protect the balance from drafts while samples are being weighed, as well to keep the delicate mechanisms free from dirt.
Early/contemporary descriptions of the features of the balance and its use are provided below:
The balance has a 6 1/2" polished aluminum beam graduated in black figures from 0 to 5 mg by 0.1 mg to both sides of the center. There is a 5 mg wire rider. The balance has knife edges on planes for the beam and both pans. The rider carrier is a wire "T" on a chrome plated rod attached to a sliding brass rod manipulated through a grommeted hole in the wood case on the right side of the balance. The beam is supported by a simple black painted column on a square black painted base plate bolted to the glass base of the balance. There is a white plastic scale attached to the front of the brass base plate graduated in red and labeled: CHRISTIAN BECKER. There is a single bullseye level inlet into the column base in front of the plastic scale. The release mechanism operates on both the beam and the pans. The pans are arrested through a second knob mounted below the heavy (1/2") black glass base, 16 1/2 x 9 1/4". The aluminum pans are supported by chrome plated brass bows and double hook hangers. The balance rests on a single rear post and two leveling screws operating brass disks set into the mahogany sub-base. The balance is enclosed in a glazed mahogany case, 16 1/2w x 13 1/2h x 9", with sliding door at the front. The instrument and case have been cleaned and waxed or oiled as appropriate. The case has a brass plaque stamped "Serial number B - 44713" on the lower front right side corner of the wooden base. At the time of acquisition there was a card tag wired to the right front leveling screw stamped "1954." There was in addition a decal labeled "State of California/Humboldt College/36461" affixed to the wood base on the lower left side beneath the black glass table. The balance was listed in the 1987 Physics/Physics Shop inventory.
An apparently identical balance, noting a smooth arrest knob and a tulip shaped rider knob both in Bakelite, in the current specimen, is shown as item 11600 "Rider Balance No. 16" equipped with equilibrium adjuster on page 33 of Catalog No. 40 Laboratory Instruments Apparatus Supplies of the Braun-Knecht-Heiman Co. (1940). The equilibrium adjuster is described on pg. 32. The HSU property inventory listed this balance as being acquired in April of 1948. It was discarded by the Physics department in the 1990's.
© R. Paselk
All photographs © R. Paselk