[USMA:25051] Re: USMA digest 1201

[Joseph B. Reid]

Jon David Galt wrote in USMA 25047:
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).


Wrong. The US gallon is defined as 231 cubic inches,

In 1896 the Committee on Weights and Measures reported that the
Treasury Department by formal order had adopted the metric standards
as the "fundamental standards" from which the customqary measures
should be derived.  This led to the definition that:
        1 meter = 39.37 inches.
The US gallon had always been 231 cubic inches,  Until 1959
        231 cubic inches = 3.785 434 497 L
In 1959, by international agreement,
        1 inch = 25.4 mm,
and     1 US gallon = 231 cubic inches
                    = 3.785 411 784 L
Federal standard 376 says the gallon is 3.785412 liters
 http://ts.nist.gov/ts/htdocs/200/202/fs376-b.pdf
It seems that US gallon was redefined by the 1959 conference of
Englush-speaking countries and as a result has shrunk by 0.0006% but
no one has complained, so far as I know.
The imperial gallon is defined as 10 pounds avoirdupois of water at 62�F.



--
Joseph B. Reid
17 Glebe Road West
Toronto  M5P 1C8                Telephone 416-486-6071