From: Wayde Allen (wallen@boulder.nist.gov)
Date: 06/12/00-10:23:46 AM Z
On Mon, 12 Jun 2000, Judy Seigel wrote:
> I used to say and write "cc" for cubic centimeter, but somehow this list
> has caused me to change to "ml", which seems the term of choice. Folks
> have said the two are different, though can that be by very much?
>
> Meanwhile, re-writing some old formulas, I changed all my "ccs" to "mls",
> but it didn't feel right and I changed them back. Now I'm wondering, does
> everybody know what a "cc" is? A "ml"? I suppose I should stick to one
> or the other, because switching could *add* confusion, but I think it's
> too late, that I have already waffled in print and online.
>
> PS: Doesn't "cc" *sound* better than "ml"? That was my reason in the
> first place: "ml" sounded like it should have "on the floss" after it.
It depends on which incarnation of the metric system you are using (cgs,
mks, SI, etc.). You can get a bit more historical detail if you want to
visit <http://physics.nist.gov/cuu/Units/history.html>. Right now the
official measurement system in use is Le Système International d'Unites or
SI system. The following is a quote from NIST Special Publication 330:
The SI or modernized metric system, long the language universally used
in science, is rapidly becoming the language of international commerce
and trade. In recognition of this fact and the increasing global nature
of the market place, the Omnibus Trade and Competitiveness Act of 1988,
which changed the name of the National Bureau of Standards (NBS) to the
National Institute of Standards and Technology (NIST) and assigned to
NIST new responsibilities for assisting industry in the development of
technology, designates ''the metric system of measurement as the
preferred system of weights and measures for United States trade and
commerce.'' Further, the Act requires ''that each Federal agency, by a
date certain and to the extent economically feasible by the end of the
fiscal year 1992, use the metric system of measurement in its
procurements, grants, and other business related activities.''
In the SI system of measurements there are seven base units (meter,
kilogram, second, ampere, kelvin, mole, candela). From these base
quantities you can derive the other measurement quantities. In the SI
system, volume is a derived quantity (cubic meter). A listing of the base
and derived units can be found at
<http://physics.nist.gov/cuu/Units/units.html>. So strictly speaking, the
liter is not an SI unit and you should use cubic centimeters.
Dave Soemarko is correct in stating the equivalence:
1L = 1 cubic decimeter = 10E-3 cubic meter
Nevertheless, the liter is a unit recognized by the SI system. Again
quoting from NIST Special Publication 330, 1991 Edition, page 20:
The CIPM (1969) recognized that users of SI will also wish to employ
with it certain units not part of it, but which are important and are
widely used. These units are given in table 8. The combination of
units of this table with SI units to form compound units should be
restricted to special cases in order not to lose the advantage of the
coherence of SI units.
The liter is listed in Table 8 which I didn't copy here. You can get a
copy of this publication by visiting
<http://physics.nist.gov/cuu/Units/bibliography.html>.
I hope that this helps.
- Wayde
(wallen@boulder.nist.gov)
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