Ivory hydrometer

Ivory hydrometer in lignum vitae case, unsigned, English, late 18th century
National Museums Scotland

Hydrometer

A hydrometer is used to measure the density of a liquid and thus its alcohol content for taxation purposes, at a given temperature. This ivory example (pictured here with its wooden case) was made in England in the late 18th century. It is unsigned.

This ivory instrument pre-dates the various brass instruments used by the government's Excise department for measuring the alcohol content of beer, wine and spirits. Made from ivory, with lead shot ballast in the extension below the hollow bulb, it has an arbitrary scale on its stem, which merely indicates the relative strength of alcoholic liquids. The wood case is made from turned lignum vitae, a tropical hardwood resistant to temperature and humidity change, which might affect the performance of the ivory hydrometer.

Experimenters found that the ivory instrument was impractical, as the porous nature of the ivory meant that the instrument was more affected by changes in temperature and relative humidity than the liquid to be measured. Later instruments were constructed in brass.


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