Editing Hydrometer (section)

===Alcoholometer===
An alcoholmeter is a hydrometer that indicates the alcoholic strength of liquids which are essentially a mixture of alcohol and water.  It is also known as a ''proof and Tralles hydrometer'' (after [[Johann Georg Tralles]], but commonly misspelled as '''traille''' and '''tralle'''). It measures the density of the fluid. Where no sugar or other dissolved substances are present, the specific gravity of a solution of ethanol in water can be directly correlated to the concentration of alcohol. Saccharometers for measuring sugar-water mixtures measure densities greater than water. Many have scales marked with volume percents of "potential alcohol", based on a pre-calculated specific gravity. A higher "potential alcohol" reading on this scale is caused by a greater specific gravity, assumed to be caused by the introduction of dissolved sugars or carbohydrate based material.  A reading is taken before and after fermentation and approximate alcohol content is determined by subtracting the post fermentation reading from the pre-fermentation reading.<ref>{{cite book |url=https://books.google.com/books?id=XRyxWu8rRnQC&q=Alcoholometer&pg=PA12 |title=The dictionary of beer and brewing|first1=Dan|last1=Rabin|first2=Carl|last2=Forget|publisher=Fitzroy Dearborn|place=London|date=1998 |isbn=9781579580780|access-date=2009-10-11 }}</ref>

These were important instruments for determining tax, and specific maker's instruments could be specified. [[Bartholomew Sikes]] had a monopoly in the UK and [[Mary Dicas]] and her family enjoyed a similar monopoly in the US.<ref>{{Cite ODNB |last=Morrison-Low |first=A. D. |url=http://www.oxforddnb.com/view/10.1093/ref:odnb/9780198614128.001.0001/odnb-9780198614128-e-49542 |title=Dicas [married name Arstall], Mary (fl. 1800–1815), maker of scientific instruments |date=2004-09-23 |volume=1 |language=en |doi=10.1093/ref:odnb/49542|isbn=978-0-19-861412-8 }}</ref>