Hydrometers

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A hydrometer is used to measure the density of a liquid for a number of different purposes, at a given temperature. This set of six hydrometers was made in the 19th century, probably by William Twaddell or his successor Thomas Twaddle, spirit proof makers based in Glasgow. The 'Twaddell' hydrometer was used in bleaching and papermaking to ascertain the specific gravity of the alkaline leys, and this form of hydrometer was apparently designed by Charles Macintosh (1766-1843), the industrialist and chemist, remembered for his waterproof coat.

The glass hydrometers have mercury-filled bases and ivory scales.

The scale on the Twaddell hydrometer enlarged the degree of specific gravity, thus enabling much more accuracy in the use of dense (and sometimes dangerous) liquids, whose properties varied depending on the atmospheric temperature.

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• Online ID: 000-190-004-180-C
• Image Rights Holder: National Museums Scotland
• Project: National Museums Scotland
  Project description   View all records in project
• Ref: National Museums Scotland  T.1925.56.6
• Date: 19th century
  c. 1840
  c. 1840
  c. 1840
  c. 1840
  c. 1840
  
• Material: Hydrometer, Twaddell's
  Hydrometer, Twaddell's
  Hydrometer, Twaddell's
  Hydrometer, Twaddell's
  Hydrometer, Twaddell's
  
• Dimensions:
• What: Hydrometer, Twaddell's
  Hydrometer, Twaddell's
  Hydrometer, Twaddell's
  Hydrometer, Twaddell's
  Hydrometer, Twaddell's
  
• Subject: 22. PHYSICS, Hydrostatics (Departmental Classification)
  22. PHYSICS, Hydrostatics (Departmental Classification)
  22. PHYSICS, Hydrostatics (Departmental Classification)
  22. PHYSICS, Hydrostatics (Departmental Classification)
  22. PHYSICS, Hydrostatics (Departmental Classification)
  
• Who: Twaddell (Eponym)
  Twaddell (Eponym)
  Twaddell (Eponym)
  Twaddell (Eponym)
  Twaddell (Eponym)
  Twaddell, Glasgow (Maker)
  Twaddell, Glasgow (Maker)
  Twaddell, Glasgow (Maker)
  Twaddell, Glasgow (Maker)
  Twaddell, Glasgow (Maker)
  
• Where: Scotland, Lanarkshire, Glasgow
  Scotland, Lanarkshire, Glasgow
  Scotland, Lanarkshire, Glasgow
  Scotland, Lanarkshire, Glasgow
  Scotland, Lanarkshire, Glasgow
  
• Event:
• Description: One of a group of six Twaddell's hydrometers on a stand - graduated 0 to 24
  One of a group of six Twaddell's hydrometers on a stand - graduated 24 to 48
  One of a group of six Twaddell's hydrometers on a stand - graduated 48 to 74
  One of a group of six Twaddell's hydrometers on a stand - graduated 74 to 102
  One of a group of six Twaddell's hydrometers on a stand - graduated 138 to 170
  
• References:
  • For the scale used by Twaddell, see R. Griffin & Co., Descriptive Catalogue of chemical Apparatus offered for sale by R. Griffin & Co, Glasgow [July 1841], p.32. 
  • For Twaddell, see D.J. Bryden, Scottish Scientific Instrument Makers 1660-1900, Edinburgh, 1972,35 
  • J. Rennie, 'Essays on Bleaching', Glasgow Mechanics' Magazine, 5 (1825-6), pp.167-8.G. Macintosh, Biographical Memoir of the late Charles Macintosh, FRS, Glasgow, 1847, p.49.R.D. Thomson, Cyclopaedia of Chemistry, London and Glasgow, 1854, p.291. 
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