Humboldt State University ® Department of Chemistry

Robert A. Paselk Scientific Instrument Museum

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Balance Demonstration Device

Mettler Inc.
HSU Chemistry Department, 1961

Usage

Apparently used to demonstrate the effects of total mass and center of mass in the determination of weight using equal-arm balances.
According to John Russell (Professor, HSU Chem. Dept., 1956-92) the device was a demonstrator provided to Mettler sales personnel. It was obtained when Arthur Smith (Professor, HSU Chem. Dept., 1948­69) requested it as part of a purchase of Mettler balances by the Department in 1960/1. As far as he could remember it was never actively used, except possibly by Dr. Smith. The box had been in the back of a shelf in the stockroom for as long as anyone could remember when it was discarded by the HSU Chemistry department stockroom in 1992.
Description: The device consists of a gold anodized Al upright column which screws into a threaded insert in the front panel of the case, and which has a small right angle shaft at the top. A turned black anodized hub equipped with ball bearings fits over the shaft. Two Al rods screw into the opposite sides of the hub, each is alternately banded in silver and black at about inch intervals. Two pairs of anodized Al spheres (one red and one blue in each pair), about 1.6 & 2.4 inches diameter, thread onto the ends of the shafts. A gold anodized Al pointer then screws into the top of the hub, while a black anodized "T" screws in below to provide adjustments for center of mass (one each slip-on (0.9") and threaded (1"), nickel-plated brass balls) and balance (slip-on, spring-held, about 1.1 inch blue anodized Al sphere). A gold anodized, quarter circle scale clamps onto the shaft through a gold anodized extension. A small (about 0.6 inch) blue anodized ball with attached short shaft slips into a hole on the top of the large blue sphere to act as a weight. The maximum overall dimensions of the assembled apparatus are 15" wide by 15" tall, excluding the base.
The device is now mounted on a custom base of 1" thick epoxy lab bench-top through a black Al pedestal threaded to fit the column. The apparatus includes the original wood case fitted with hardwood compartments contoured to the various components (the hinges are missing and have been replaced with tape, but the latches are present on either side, though rusty).

The Chemical Balance at Humboldt

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HSTC (1921-34)
HSC 54-73 icon
HSC (1954-1973)
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HSC (1935-1953)

HSC 1956-72 Instrument Collection

© R. Paselk
Last modified 13 August 2010