cubic VVV

[James Smith]

Chris,

Point well made.  I should have used a more current
and accurate "Accurate current reference".  The
1971-1972 CRC Handbook of Chemistry and Physics still
has 1 liter = 1000.028 cubic centimeters.

But, as a deciliter is a tenth of a liter, a liter
must be exactly ten deciliters.  I was not trying to
define the liter but pointing out a simple rational
relationship; frankly, looking back through the thread
of this discussion, I don't recall why I thought it
was even pertinent!

--- Chris Waigl <cwaigl at FREE.FR> wrote:

> James Smith wrote:
>
> >No, actually a liter is the volume of exactly 1 kg
> of
> >pure water at 3.98 °C and under a pressure of 1
> atm.
> >It is also exactly ten deciliters.
> >
> It can't be both. It would also be improper to
> define an SI unit in two
> different, (potentially and actually) conflicting
> ways.
>
> >However, because
> >of a measurement error early in the merification
> >process, 1 liter equals 1.000027 cubic decimeters.
> >Within the limits of accuracy for most real-world
> >measurements, the difference is negligible.
> >Accurate current reference works give 1 liter =
> >1.000027 cubic decimeter = 1000.027 cubic
> centimeters
> >and 1 milliliter = 1.000027 cubic centimeter.
> >
> >
> What you are describing is the state of affairs
> between 1901 and 1964.
> In 1964, the liter reverted to its original
> definition as exactly 1
> cubic decimeter = 1000 cubic centimeters = 1/1000
> cubic meter.
>
> Meanwhile, in 1960, the meter, too, was redefined
> without reference to
> the meter bar (which itself was build with reference
> to a measurement of
> the earth's meridian; an alternative reference to
> periods of a pendulum
> was used, too, in the 18th century); this definition
> was again revised
> in 1983. The current meter definition relies on time
> measurement only
> (plus a universal constant).
>
> >As I understand - but I may be mislead on this part
> of
> >the tale - in the original metric scheme there was
> no
> >liter, the cubic centimeter was the standard of
> volume
> > and the liter came to be because of this
> measurement
> >error.
> >
> >
> In my understanding, the original liter definition
> was precise (and
> identical in its formulation with today's, i.e. it
> didn't rely on any
> measurements), but it was the kilogram definition
> that depended on the
> precise measurement of the mass of 1 liter of pure
> water at a given
> temperature and atmospheric pressure. That's where
> the measurement error
> struck. Even today, with the iridium cylinder that
> serves as the
> kilogram standard, the kilogram is still the iffiest
> SI base unit. There
> are several proposals for a redefinition, one of
> which will without
> doubt be adopted one day.
>
> (The liter is not the standard of volume. That's the
> cubic meter.
> "Liter" is just a shorthand for 1/1000 m^3.)
>
> Chris Waigl
>
> --
> blog:      http://serendipity.lascribe.net/
> eggcorns:  http://eggcorns.lascribe.net/
>

James D. SMITH                 |If history teaches anything
South SLC, UT                  |it is that we will be sued
jsmithjamessmith at yahoo.com     |whether we act quickly and decisively
                               |or slowly and cautiously.




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