Humboldt State University ® Department of Chemistry

Robert A. Paselk Scientific Instrument Museum

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Precision Double-Hook Torsion Balance

Roller-Smith, Inc.
No. 705796
HSU Chemistry Department, 1960

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This balance is designed for the rapid determination of weights of small objects (<1.5 gm) to a reasonably high precision (±0.25 mg). Though of very narrow range, its ease of operation, as seen in the operating instructions, made it a popular instrument. Weights from 0-500 mg are determined directly by adjusting the dial, weights to 1.5 g are made by adding a 0.500 or 1.000 g weight included with the balance.


This instrument is a low capacity precision torsion balance. The hammertone gray enameled metal case has a "mantel-clock" like shape, with a flat base sitting on a rod (left rear) and three adjusting screw feet (front and right rear). The instrument is 10.5" high, and 6" x 12" wide across the base. A handle with finger pad turns a cursor with a vernier (0-2 x .2 mg) through a range of 500 mg x 2 mg with numbered graduations at every 50 mg on the central circular scale. There is a zero adjust lever on the back center of the case. The dail/scale appears to be of card with the scale printed on it. Above the center hole of the dial is printed IN LARGE CAPS: PRECISION BALANCE. Beneath this is printed in small caps: CAPACITY 500 MG 1 DIVISION 2 MG / CALIBRATED WITH -0- ON WEIGHING HOOK. Below the center hole in the dial is printed in medium caps: ROLLER-SMITH, INC. Then in small caps: SUBDIVISION OF / FEDERAL PACIFIC ELECTRIC CO. / NEWARK, N.J., U.S.A. / NO. 705796. At the bottom edge of the dial is printed: N.P. 1918. An arrest lever is placed on the case below and to the right of the 500 of this scale. Balance is achieved through aligning a floating, angled, needle against a broken line adjacent to a small mirror. There are enclosed sample and weight compartments on the opposite sides of the case. In each a window allows viewing of the contents. The sample pan is one-piece aluminum foil bent to form a trough to hold the samples and cut into a hook at the top. A rectangle of aluminum foil of precisely equal mass is hung on the opposite hook through a punched hole to act as a counter weight. Additional brass weights may be added to this hook to increase the capacity of the balance. All exposed metal parts on the case are nickel plated, the feet are aluminum. The is a bullseye level in the base just below the center of the dial. There is a manufacturers tag riveted to the center of the front edge of the base: FEDERAL PACIFIC ELECTRIC CO. / FIFTY AVENUE L, INC. /NEWARK I. N.J. U.S.A. The instrument is in excellent, working condition.
The balance includes a custom fitted "sewing machine type" case (13 1/2 x 7 1/2 x 12" h) covered in black leatherette. There is a black plastic suitcase type handle on top.


A very similar balance is shown as item 11725: Balance, Precision Weighing, Double Hook, on pp 42-43 of the Braun-Knecht-Heiman-Co. (Division of Van Waters & Rogers, Inc.) Catalog No 63, Laboratory Instruments Apparatus and Supplies. San Francisco. (1961). A new style is shown in the 1963 Shaar catalog, which is seen again in the 1968 Scientific Products catalog, and the 1980 Fisher Scientific Catalog.

The Chemical Balance at Humboldt

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HSTC (1921-34)
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HSC (1954-1973)
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HSC 1956-72 Instrument Collection

© R. Paselk
Last modified 13 August 2010