>AFAIK, the US gallon is precisely defined as 5/6 imperial gallon, and >the imperial gallon is exactly 10 pounds of water (presumably at 4C).
I don't know if the US has a definition of an imperial gallon. The following two countries have official definitions at: Ireland - Metrology Act 1996: http://193.120.124.98/gen531996a.html UK - Units of Measurement Regulations 1995: www.hmso.gov.uk/si/si1995/Uksi_19951804_en_2.htm
