Humboldt State University ® Department of Chemistry

Robert A. Paselk Scientific Instrument Museum

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Analytical Balance Weight Set

Class S, NBS Certified

William Ainsworth

provenance: Humboldt College; c.1961

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Class S weights are intended as standards and for highest quality work. This set includes rodium plated bronze 1–100 g weights, aluminum 1 - NBS (now NIST) certification adds significantly to the cost of a weight set. Unfortunately even unused weights can change mass, so these would need recalibration to continue use as standards.

Descriptions of Weights and their use are provided in the links below:


The set consists of a plastic box containing Class S rhodium-plated brass 1–100 g weights, tantalum 50–500 mg fractional weights, aluminum 1–10 mg fractional weights, and two aluminum wire 10 mg riders. The set is complete including Ainsworth plastic forceps. Most of the weights remain undisturbed in their original tissue paper wrappings.
The plastic box has the company name in raised letters on the lid. There is a Class S Metric sticker on the lid and "NBS TESTNO. 170476 SET A" is stamped and filled with green pigment across the top of the lid (see linked photo). The box is filled with a one piece solid wood block with holes for the various weights etc. Weight compartments are lined with polyethylene sleeves, most of the weights remain in their original wrappers. There is an unlined forceps slot, and an black plastic tray with clear glass cover tray for fractional weights. A certificate was folded and inserted into the lid above the weights (now stored in museum files in an archival sleeve). A linked scan of this certificate is availble for viewing. The collection also includes the original Ainsworth and NBS wrappings. You may view a scan of the Ainsworth and NBS wrappings at this link. The ribbon was sealed with wax.

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