The comments made by Leigh and John about my "chemistry viewpoint of
weight" are certainly on target. I also think Brian is correct that
the chemists' view of g is 9.80665, and this is the sea-level
45-degrees-latitude accepted value.
A couple further comments.
I don't want to imply that chemists spend large amounts of time doing
altitude or latitude or other types of weight/mass corrections. They
don't have to. Analytical balances used by chemists are either
equal-arm balances, or some other design that allows a direct mass
comparison with standard masses. Therefore, if the balance is used
correctly (which might only require turning it on) everything that
needs to be accounted for is automatically accounted for, except
buoyancy. Therefore, typically, the only difference between the
apparent mass and the true mass is the buoyancy.
Although many chemists routinely say they weigh things and use the
wording "apparent weight," the more careful chemists usually approach
an analytical balance with the words "I am going to mass this." And
the number they record is recorded as the "apparent mass." I try to do
this myself, but the tendency to say I'm going to weigh something is
certainly ingrained.
Many chemists are also trying to refer to atomic mass and molecular
mass rather than atomic weight and molecular weight. Progress is being
made, but it is difficult.
We also find it difficult to refer to our box of shiny metal objects as
"calibration masses" rather than the less appropriate "calibration
weights." A quick look in catalogs shows that they are advertised and
sold as weights, and some are certified by NIST as weights.
When we had balances reading only in grams, we didn't have the new
problem of "balances" that can give readings in ounces, pounds,
newtons, etc. Some do not offer readings in newtons, and they
interpret ounces and pounds as "ounce-mass" and "pound-mass." If the
instruction manual explains what is happening, it says that the basic
quantity being measured (i.e. the internal units) is mass in grams.
The microprocessor then converts the gram reading into ounces or
pounds. When performing the conversion, the conversion factors used
are well defined and seem to be based upon an accepted ratio between
kilograms and slugs along with an accepted value of g of 9.80665 m/s^2.
Michael D. Edmiston, Ph.D. Phone/voice-mail: 419-358-3270
Professor of Chemistry & Physics FAX: 419-358-3323
Chairman, Science Department E-Mail edmiston@bluffton.edu
Bluffton College
280 West College Avenue
Bluffton, OH 45817