Accession No
6257
Brief Description
Set of six mercury-in-glass hydrometers with measuring vessel, in fitted case, c. 1940
Origin
Maker
Class
weights & measures; metrology
Earliest Date
1935
Latest Date
1965
Inscription Date
Material
glass; metal (mercury; brass); wood; leather; cloth (felt)
Dimensions
Width: 210mm , Length: 320mm, Depth: 50mm
Special Collection
Provenance
Donated from an individual at the Department of Zoology, Downing Street, Cambridge, 23/10/2008. Originally from Entymology Division of Cambridge University Zoology Department.
Inscription
[On top of case]
ENT. 31
Description Notes
Set of six mercury-in-glass hydrometers with measuring vessel, in fitted case, c. 1940. From Entomology Division of Cambridge University Zoology Department.
Set contained in a fitted case lined with blue felt. Each hydrometer is held in place by raised dividers. The measuring vessel is held in the largest divider.
The measuring vessel is a glass cylinder with a brass base. Each hydrometer is a thin sealed glass tube, with a sealed bulb at their base containing varying amounts of mercury. Each hydrometer has a different graduated scale indicating specific gravity, and labelled to show that operation temperature should be 40 oF. The six scales of specific gravity are:
700 - 840
860 - 1000
1000 - 1200
1200 - 1400 [Labelled with the word ‘Foreign’]
1400 - 1600
1800 - 2000
One hydrometer is missing from the set (presumably 1600 - 1800), as is the thermometer, which would have sat in the empty slim slot next to the measuring vessel.
Condition: good/fair - incomplete
References
Events
Description
A hydrometer is used to measure the precise gravity (or density) of liquids. To measure the density, the liquid to be tested is poured into a jar, and the hydrometer is lowered into it until it floats freely. When the surface of the liquid touches the stern, the point is noted down. Usually, a paper scale is inside the stern, allowing the specific gravity to be read directly.
FM:46735
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