"Karats" measured by weight or volume?

"Dale Hallmark" wrote in message
...

"Don A. Gilmore" wrote in message
...
Hi guys:

Are karats (like of gold) measured by weight or by volume? Most of what
I
read implies that karats are measured by weight (24k being pure gold),
but
that just doesn't make any sense. If karats are determined by weight,
you
would have to know exactly what the alloying metals were to determine
it.
If karats were by volume, they would be universal, regardless of
alloying
elements.

Which is right?

Don
Kansas City


Neither weight nor volume. It is a measure of purity.
Take the karats and divide by 24 and multiply by 100
and you have percent Gold content.


You guys are not following me. The purity has to be measured somehow:
either weight or volume.

Here's an example. If I take one cubic inch of gold and one cubic inch of
aluminum and mix them together I should get two cubic inches of alloy that
has a purity of 12 karats (50% of 24), but ONLY if I'm measuring karats by
volume.

One cubic inch of gold weighs .6969 lbs. One cubic inch of aluminum weighs
..0975 lbs. So the total weight of the 2.0 cu. in. of alloy is .6969 + .0975
= .7944 lbs. So the percentage of gold by WEIGHT would be

..6969 / .7944 = 87.7%

Gold accounts for 87.7% of the total weight of the alloy. This results in a
karat of

..877 x 24 = 21.05k (by weight)

which is nowhere close to the "volumetric" karat of 12k.

Now, let's say I mix one cubic inch of gold with one cubic inch of copper.
Volumetrically I still have half gold, or 12k. But a cubic inch of copper
weighs .3210 lbs. So the total weight of the alloy is .6969 + .3210 = 1.018
lbs. and the percentage of gold by WEIGHT is

..6969 / 1.018 = 68.5% = 16.4k

So by changing the alloying metal I have considerably changed the karat, if
indeed we are to use weight to determine karat, even though the size of the
resulting alloy (2.0 cu. in.) is the same.

Now do you get what I mean?

Don
Kansas City

On Fri, 29 Oct 2004 18:14:43 -0700, in ôõ "Don A. Gilmore"
wrote:

You guys are not following me. The purity has to be measured somehow:
either weight or volume.


right.

Karat content by itself does not indicate how much metal there is, but the proportion
of gold to base metals, expressed in 24ths. And as such, one must specify whether
that proportion is measured by volume, or by weight.

The answer is simply that it's done by weight.

an ounce of 18K gold contains 3/4 ounce of gold, and 1/4 ounce of base metal. The
relative volumes involved will vary widely depending on which base metals. And
sometimes it's surprising in other ways. 18K rose gold made of just gold and copper,
for example, will have 3 times as much gold as there is copper by weight. But the
ratio of gold atoms to copper atoms is very nearly 1:1 And the physical volumes of
the two will be yet another ratio.

But weight is the one we use.

Peter

Hi guys:

Are karats (like of gold) measured by weight or by volume?

Weight

Abrasha
http://www.abrasha.com

On Fri, 29 Oct 2004 18:14:43 -0700, in ?? "Don A. Gilmore"
wrote:

You guys are not following me. The purity has to be measured somehow:
either weight or volume.

As has already been said, the answer is by weight. But it may be interesting to also
note that it's a good thing this is so. Volume of solid materials is often tricky
to determine. One can use displacement of a liquid, but that's about the only
relatively easy way to do it, and it presupposes that one has a sufficiently accurate
means to measure that displacement, and in practice, it's actually not that simple.
Certainly not as simple as weighing. Consider, just for illustration, what happens
if you attempt to measure volume the way one does it in the kitchen. How many cups
of this, or that, etc. Or him many milileters, if you prefer a more precise unit.
If the metal to be measured is in find grains of sand, the cup will hold a certain
amount. If the metal is in a mix of large solids and fine grains, it will hold more,
as the voids between the solid particles are filled with the sand, a mix of metal and
the air spaces between grains. If the metal is only in large pieces, each slightly
more than half the diameter of the container, then you won't get much in the
container. Volume turns out to be tricky indeed, to measure when it's not a single
solid mass in a nice uniform geometric shape like a cube or a sphere.

Here's an example. If I take one cubic inch of gold and one cubic inch of
aluminum and mix them together I should get two cubic inches of alloy that
has a purity of 12 karats (50% of 24), but ONLY if I'm measuring karats by
volume.

And this particular illustration is also quite useful. You see, most of the metals
we mix with gold are, to some degree or another, soluable in gold, and vice versa.
The alloys are not mixes of crystals of single metals, but rather mixes of several
compositions, each one a solid solution. the density of the alloy overall, which
would relate composition to volume, is not exactly the same for each mix, nor always
predictable based on the metals mixed together. The reason is that the volume, and
density of the mix, depends on the atomic weights of the atoms, and also on the
distance between the atoms. This is constant for a single metal in it's known usual
crystal structure. But solid solutions of metals have their own unique structures,
and the end density of an alloy is not automatically an exact mathematical product of
the densities (or volumes) of the metals you mix. The example you cite, of aluminum
and gold, is especially good for this illustration, since in this case, it turns out
that gold and aluminum are completely insoluable in each other. Like oil and water,
they don't just mix. However, they do combine, if you mix an approximate 18K mix of
the two using WEIGHTS, not volumes, forming not a metallic alloy in the normal sense,
but an actual chemical compound of sorts, a structure callled an intermetallic. It
does not have the usual face centered cubic crystal structure of normal gold alloys,
and as such, the distances between atoms in that structure differs from those
distances in the parent pure metals. Thus the specific gravity/density of the mix,
and thus it's volume, is not quite what one would predict using your method above.
Also, of interest to jewelers, it turns out to be bright purple in color, and
totally brittle and unlike a metal in it's working properties.

Another combination that can be interesting is an 18K mix of gold and copper. Though
there's three times the weight of gold to the copper, it turns out that this is
almost a 1:1 ratio of gold to copper atoms, and it also turns out that within a
certain temperature range, this mix also forms a different structure than the normal
solid solutions of one in the other. It forms an ordered array, where the atoms form
as alternating layers of copper and gold, like stacked sheets of paper. Again, the
crystal structure of this mix is no longer the face centered cubic structure that
both metals normally have, and that the usual solid solution forms also usually have.
When the structured array forms, the density of the metal, and it's volume, changes
very slightly.

And yet another problem with volumetric determinations. In order to get any
consistancy, one would also have to specify a temperature at which to measure the
volume. Can you imagine the problems involved if you could only alloy your metals at
a single reliable temperature? All the different metals expand and contract with
changes in temperature, and each has it's own rate of expansion and contraction. So
one's Karat measurements, if based on volume would only be accurate at certain temps.
I can see it now... "yes maam. This ring is indeed 14K gold. So long as the
temperature is 68.3 degrees F. " Hmm. Wouldn't that be fun.

Peter

Don,
It must be measured by the weight percentage, otherwise we were lost.
When you purchase gold, in any purity, you pay by the weight. You then
know that the 1 gr of 18k gold purchased (for example) contains 0.75
gr pure gold. In the same way, when you need to recycle a jewelry, you
know exactly how much pure gold you are going to obtain regardless of
the exact metal composition and color of the gold to be refined.
Can you imagine the situation had it been defined by volume
percentage? We all had to be mathematicians and/or chemists....
Sarit.

Sarit Wolfus - Silver, Gold and Gemstones, handcrafted jewelry.
http://sarit-jewelry.com



"Don A. Gilmore" wrote in message
. ..
"Dale Hallmark" wrote in message
...

"Don A. Gilmore" wrote in message
...
Hi guys:

Are karats (like of gold) measured by weight or by volume? Most of what
I
read implies that karats are measured by weight (24k being pure gold),
but
that just doesn't make any sense. If karats are determined by weight,
you
would have to know exactly what the alloying metals were to determine
it.
If karats were by volume, they would be universal, regardless of
alloying
elements.

Which is right?

Don
Kansas City


Neither weight nor volume. It is a measure of purity.
Take the karats and divide by 24 and multiply by 100
and you have percent Gold content.


You guys are not following me. The purity has to be measured somehow:
either weight or volume.

Here's an example. If I take one cubic inch of gold and one cubic inch of
aluminum and mix them together I should get two cubic inches of alloy that
has a purity of 12 karats (50% of 24), but ONLY if I'm measuring karats by
volume.

One cubic inch of gold weighs .6969 lbs. One cubic inch of aluminum weighs
.0975 lbs. So the total weight of the 2.0 cu. in. of alloy is .6969 + .0975
= .7944 lbs. So the percentage of gold by WEIGHT would be

.6969 / .7944 = 87.7%

Gold accounts for 87.7% of the total weight of the alloy. This results in a
karat of

.877 x 24 = 21.05k (by weight)

which is nowhere close to the "volumetric" karat of 12k.

Now, let's say I mix one cubic inch of gold with one cubic inch of copper.
Volumetrically I still have half gold, or 12k. But a cubic inch of copper
weighs .3210 lbs. So the total weight of the alloy is .6969 + .3210 = 1.018
lbs. and the percentage of gold by WEIGHT is

.6969 / 1.018 = 68.5% = 16.4k

So by changing the alloying metal I have considerably changed the karat, if
indeed we are to use weight to determine karat, even though the size of the
resulting alloy (2.0 cu. in.) is the same.

Now do you get what I mean?

Don
Kansas City

"Don A. Gilmore" wrote in message
...

You guys are not following me. The purity has to be measured somehow:
either weight or volume.

Weight

Volume varies with temperature and metals don't all expand at the same rate.

Weight doesn't.

The 'filler' used with gold is usually silver with copper added for colour,
'rose' gold has more copper in it...

--
William Black
------------------
Strange women lying in ponds distributing swords
is no basis for a system of government

Dale,
Neither, as precisely, it is mass. The weight of an object = m (mass) x g
(acceleration of gravity).Weight is the force exerted by the mass of the
object due to gravitational attraction.
Depending upon where you are on the earth, the weight is not a constant, but
mass Always is. (unless you are approaching the speed of light, which isn't
likely)
Density has a buoyancy effect in the measurement of both mass and weight,
where differing densities of equal mass displace different volumes (and
masses) of air, but in your case, the difference will be immeasureable. ( I
do see the difference in my measurements, as I do take it into account when
comparing very precise mass standards)
So, it's Mass...

More confusing facts:
1 ounce Gold = 31.1035 grams (Troy ounce) Precious metals only are
measured in Troy units
1 ounce Aluminum = 28.349523 grams (Avoirdupois ounce) Everything else is in
A
1 pound Gold = 12 oz Troy = 373.242 grams
1 pound Aluminum = 16 oz Avoirdupois = 453.592368 grams

Howie
Metrology is my game.

"Don A. Gilmore" wrote in message
...
"Dale Hallmark" wrote in message
...

"Don A. Gilmore" wrote in message
...
Hi guys:

Are karats (like of gold) measured by weight or by volume? Most of
what
I
read implies that karats are measured by weight (24k being pure gold),
but
that just doesn't make any sense. If karats are determined by weight,
you
would have to know exactly what the alloying metals were to determine
it.
If karats were by volume, they would be universal, regardless of
alloying
elements.

Which is right?

Don
Kansas City


Neither weight nor volume. It is a measure of purity.
Take the karats and divide by 24 and multiply by 100
and you have percent Gold content.


You guys are not following me. The purity has to be measured somehow:
either weight or volume.

Here's an example. If I take one cubic inch of gold and one cubic inch of
aluminum and mix them together I should get two cubic inches of alloy that
has a purity of 12 karats (50% of 24), but ONLY if I'm measuring karats by
volume.

One cubic inch of gold weighs .6969 lbs. One cubic inch of aluminum
weighs
.0975 lbs. So the total weight of the 2.0 cu. in. of alloy is .6969 +
.0975
= .7944 lbs. So the percentage of gold by WEIGHT would be

.6969 / .7944 = 87.7%

Gold accounts for 87.7% of the total weight of the alloy. This results in
a
karat of

.877 x 24 = 21.05k (by weight)

which is nowhere close to the "volumetric" karat of 12k.

Now, let's say I mix one cubic inch of gold with one cubic inch of copper.
Volumetrically I still have half gold, or 12k. But a cubic inch of copper
weighs .3210 lbs. So the total weight of the alloy is .6969 + .3210 =
1.018
lbs. and the percentage of gold by WEIGHT is

.6969 / 1.018 = 68.5% = 16.4k

So by changing the alloying metal I have considerably changed the karat,
if
indeed we are to use weight to determine karat, even though the size of
the
resulting alloy (2.0 cu. in.) is the same.

Now do you get what I mean?

Don
Kansas City

Howard Fairchild wrote:

Dale,
Neither, as precisely, it is mass. The weight of an object = m (mass) x g
(acceleration of gravity).Weight is the force exerted by the mass of the
object due to gravitational attraction.
Depending upon where you are on the earth, the weight is not a constant, but
mass Always is. (unless you are approaching the speed of light, which isn't
likely)
Density has a buoyancy effect in the measurement of both mass and weight,
where differing densities of equal mass displace different volumes (and
masses) of air, but in your case, the difference will be immeasureable. ( I
do see the difference in my measurements, as I do take it into account when
comparing very precise mass standards)
So, it's Mass...

More confusing facts:
1 ounce Gold = 31.1035 grams (Troy ounce) Precious metals only are
measured in Troy units
1 ounce Aluminum = 28.349523 grams (Avoirdupois ounce) Everything else is in
A
1 pound Gold = 12 oz Troy = 373.242 grams
1 pound Aluminum = 16 oz Avoirdupois = 453.592368 grams

Howie
Metrology is my game.

"Don A. Gilmore" wrote in message
...

"Dale Hallmark" wrote in message
...

"Don A. Gilmore" wrote in message
...

Hi guys:

Are karats (like of gold) measured by weight or by volume? Most of
what

I

read implies that karats are measured by weight (24k being pure gold),

but

that just doesn't make any sense. If karats are determined by weight,

you

would have to know exactly what the alloying metals were to determine

it.

If karats were by volume, they would be universal, regardless of

alloying

elements.

Which is right?

Don
Kansas City


Neither weight nor volume. It is a measure of purity.
Take the karats and divide by 24 and multiply by 100
and you have percent Gold content.


You guys are not following me. The purity has to be measured somehow:
either weight or volume.

Here's an example. If I take one cubic inch of gold and one cubic inch of
aluminum and mix them together I should get two cubic inches of alloy that
has a purity of 12 karats (50% of 24), but ONLY if I'm measuring karats by
volume.

One cubic inch of gold weighs .6969 lbs. One cubic inch of aluminum
weighs
.0975 lbs. So the total weight of the 2.0 cu. in. of alloy is .6969 +
.0975
= .7944 lbs. So the percentage of gold by WEIGHT would be

.6969 / .7944 = 87.7%

Gold accounts for 87.7% of the total weight of the alloy. This results in
a
karat of

.877 x 24 = 21.05k (by weight)

which is nowhere close to the "volumetric" karat of 12k.

Now, let's say I mix one cubic inch of gold with one cubic inch of copper.
Volumetrically I still have half gold, or 12k. But a cubic inch of copper
weighs .3210 lbs. So the total weight of the alloy is .6969 + .3210 =
1.018
lbs. and the percentage of gold by WEIGHT is

.6969 / 1.018 = 68.5% = 16.4k

So by changing the alloying metal I have considerably changed the karat,
if
indeed we are to use weight to determine karat, even though the size of
the
resulting alloy (2.0 cu. in.) is the same.

Now do you get what I mean?

Don
Kansas City


Perfect explanation!

Best whishes,
Heinrich Butschal

--
www.juwelen.online-boerse.org
www.meister-atelier.de
www.schmuckfabrik.de
www.medico.butschal.de

On Tue, 02 Nov 2004 02:18:52 GMT, "Howard Fairchild"
wrote:

Dale,
Neither, as precisely, it is mass. The weight of an object = m (mass) x g
(acceleration of gravity).Weight is the force exerted by the mass of the
object due to gravitational attraction.

No, Howard, you are the one who is confused by the various different
meanings of the ambiguous word "weight."

Weight is never a force when anybody talks about "troy weight."
That's one way in which the troy units of weight differ from their
avoirdupois cousins, and from grams and kilograms as well--they have
never spawned units of force of the same name.

Weight is never a force when anybody talks about "carat weight" either
(5 carats = 1 gram).

Weight is never a force when anybody talks about "net weight" of
anything, nor about the "tare weight" of its container. When my
ketchup bottle says "Net wt. 24 oz (1 lb 8 oz) 680 g" those pounds and
ounces are every bit as much units of mass as the grams which appear
right alongside them.

NIST Special Publication 811,
http://physics.nist.gov/Pubs/SP811/sec08.html

Thus the SI unit of the quantity weight used in this
sense is the kilogram (kg) and the verb "to weigh" means
"to determine the mass of" or "to have a mass of".

Examples: the child's weight is 23 kg
the briefcase weighs 6 kg
Net wt. 227 g

The National Standard of Canada, CAN/CSA-Z234.1-89 Canadian Metric
Practice Guide, January 1989, says something similar:

5.7.3 Considerable confusion exists in the use of
the term "weight." In commercial and everyday use,
the term "weight" nearly always means mass. In
science and technology, "weight" has primarily
meant a force due to gravity. In scientific and
technical work, the term "weight" should be
replaced by the term "mass" or "force," depending
on the application.

5.7.4 The use of the verb "to weigh" meaning "to
determine the mass of," e.g., "I weighed this object
and determined its mass to be 5 kg," is correct.

NPL FAQ
http://www.npl.co.uk/force/faqs/forcemassdiffs.html

Weight
In the trading of goods, weight is taken to mean the
same as mass, and is measured in kilograms. Scientifically
however, it is normal to state that the weight of a body
is the gravitational force acting on it and hence it should
be measured in newtons, and this force depends on the
local acceleration due to gravity. To add to the confusion,
a weight (or weightpiece) is a calibrated mass normally
made from a dense metal, and weighing is generally
defined as a process for determining the mass of an
object.

So, unfortunately, weight has three meanings and care
should always be taken to appreciate which one is
meant in a particular context.

American Society for Testing and Materials, Standard for Metric
Practice, E 380-79, ASTM 1979:

3.4.1.2 Considerable confusion exists in the use of
the term weight as a quantity to mean either force
or mass. In commercial and everyday use, the term
weight nearly always means mass; thus, when one
speaks of a person's weight, the quantity referred
to is mass. . . .

later the same section in ASTM E 380-79 concludes with the following
advice:
Because of the dual use of the term weight as a
quantity, this term should be avoided in technical
practice except under circumstances in which its
meaning is completely clear. When the term is
used, it is important to know whether mass or
force is intended and to use SI units properly as
described in 3.4.1.1, by using kilograms for mass
or newtons for force.


Depending upon where you are on the earth, the weight is not a constant, but
mass Always is. (unless you are approaching the speed of light, which isn't
likely)
Density has a buoyancy effect in the measurement of both mass and weight,
where differing densities of equal mass displace different volumes (and
masses) of air, but in your case, the difference will be immeasureable. ( I
do see the difference in my measurements, as I do take it into account when
comparing very precise mass standards)
So, it's Mass...

Of course it is mass. That doesn't mean it is not weight.

--
Gene Nygaard
"It's not the things you don't know
what gets you into trouble.

"It's the things you do know
that just ain't so."
Will Rogers

Since in an alloy both components are in the same place, the gravitational
constant will be the same for both components so the ratio of their weight
will be the same as the ratio of their masses. Weight seems OK to use here.

Chunk

"Howard Fairchild" wrote in message
...
Dale,
Neither, as precisely, it is mass. The weight of an object = m (mass) x g
(acceleration of gravity).Weight is the force exerted by the mass of the
object due to gravitational attraction.
Depending upon where you are on the earth, the weight is not a constant,
but
mass Always is. (unless you are approaching the speed of light, which
isn't
likely)
Density has a buoyancy effect in the measurement of both mass and weight,
where differing densities of equal mass displace different volumes (and
masses) of air, but in your case, the difference will be immeasureable.
( I
do see the difference in my measurements, as I do take it into account
when
comparing very precise mass standards)
So, it's Mass...

More confusing facts:
1 ounce Gold = 31.1035 grams (Troy ounce) Precious metals only are
measured in Troy units
1 ounce Aluminum = 28.349523 grams (Avoirdupois ounce) Everything else is
in
A
1 pound Gold = 12 oz Troy = 373.242 grams
1 pound Aluminum = 16 oz Avoirdupois = 453.592368 grams

Howie
Metrology is my game.

"Don A. Gilmore" wrote in message
...
"Dale Hallmark" wrote in message
...

"Don A. Gilmore" wrote in message
...
Hi guys:

Are karats (like of gold) measured by weight or by volume? Most of
what
I
read implies that karats are measured by weight (24k being pure
gold),
but
that just doesn't make any sense. If karats are determined by
weight,
you
would have to know exactly what the alloying metals were to determine
it.
If karats were by volume, they would be universal, regardless of
alloying
elements.

Which is right?

Don
Kansas City


Neither weight nor volume. It is a measure of purity.
Take the karats and divide by 24 and multiply by 100
and you have percent Gold content.


You guys are not following me. The purity has to be measured somehow:
either weight or volume.

Here's an example. If I take one cubic inch of gold and one cubic inch
of
aluminum and mix them together I should get two cubic inches of alloy
that
has a purity of 12 karats (50% of 24), but ONLY if I'm measuring karats
by
volume.

One cubic inch of gold weighs .6969 lbs. One cubic inch of aluminum
weighs
.0975 lbs. So the total weight of the 2.0 cu. in. of alloy is .6969 +
.0975
= .7944 lbs. So the percentage of gold by WEIGHT would be

.6969 / .7944 = 87.7%

Gold accounts for 87.7% of the total weight of the alloy. This results
in
a
karat of

.877 x 24 = 21.05k (by weight)

which is nowhere close to the "volumetric" karat of 12k.

Now, let's say I mix one cubic inch of gold with one cubic inch of
copper.
Volumetrically I still have half gold, or 12k. But a cubic inch of
copper
weighs .3210 lbs. So the total weight of the alloy is .6969 + .3210 =
1.018
lbs. and the percentage of gold by WEIGHT is

.6969 / 1.018 = 68.5% = 16.4k

So by changing the alloying metal I have considerably changed the karat,
if
indeed we are to use weight to determine karat, even though the size of
the
resulting alloy (2.0 cu. in.) is the same.

Now do you get what I mean?

Don
Kansas City