Usage: 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.
Description: 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.
Research: 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.
