"Karats" measured by weight or volume?

Dear Sir,

normally 1 karat is equal of 0,2 grams. Doesn't matter of gold or brilliants/diamonds. IMHO :-))

Best regards Nick

"Don A. Gilmore" ÓÏÏÂÝÉÌ/ÓÏÏÂÝÉÌÁ × ÎÏ×ÏÓÔÑÈ ÓÌÅÄÕÀÝÅÅ: news: snipped-for-privacy@uni-berlin.de...

Huh?? So a 22 karat gold coin only has 0.2 g of gold in it regradless of size? NONSENSE.

Don Kansas City

24 Karat gold = 100% gold by weight

12 Jarat Gold alloy = 50% gold by weight

) Karat Gold Alloy = o% gold by weight

What the prior poster told you -- before you copied this over to this newsgroup, was quite correct.

You can actually look the darn thing up by just typic Karat into Google and clicking the definition.

Are you an engineer, by any chance?

Pay attention!

1. Karat with a "K" is a measure of purity.

1. Carat with a "C" is a measure of weight.

2. Carrot is a vegetable.

Diamond Jim

Correct!

24K(arats) gold means it's 100% pure gold. 18K(arats) means it is only 75% pure, 12K(arats) means it's only 50% gold by content,...and so on..

True! Carats is a measure of weight used for gems or precious stones. One carat is one-fifth of a gram. So if if you have a diamond weighing 1 gram it is designated as a 5-carat diamond.

I believe so too. :)

SNIP

When two materials are combined the new volume is almost never the sum of the original volumes, be it copper with gold or salt with water. The resulting volumes are not necessarily linear with the percentage of the components. That's why gold purity is based on the mass of the metals combined and the old system used Karats which are parts gold per 24 parts of total alloy by wieght.

KC

Settles the issue:

I notice that in niether of your references does the term Karat get defined as to whether it is by wieght or by volume. I am not criticizing you but do believe that such definitions confuse some people. Is the word "part" always supposed to mean a wieght? Perhaps we technical people accept that wieght is understood in discussions of percent unless told otherwise. Medical and chemical solutions are sold as w/v %, i.e. 5 grams per 100 ml. If the original question was posed by a chef I can see how he would think in terms of volumes of ingredients.

KC

I think, "a karat has nothing to do with weight, but instead refers to the quantity of gold contained in a particular item. The measurement uses a base of 24 units. Pure gold is twenty-four twenty-fourths (24/24ths) gold, and is called 24-karat gold" means volume, although it is not 100% obvious. If one assumes that a karat is not a measure of weight, as cited above, then he next assumption would be that all 24 units have to be equal in some unit. What other unit is there besides volume that could be used to measure a unit of gold?

Moles?

Don Kansas City

The problem with "karats" and weight-percent for "solid state" folks, is that you are being ripped off. The atomic weight of Au is almost three times that of Cu, and twice that of Ag.

1 atom of Au to 1 atom of Cu, would be 50-50 atomic percent. However, by weight percent it is closer to 78% or 19 Karat. That means you buy 3/4 Au and only really get 1/2 Au.

For Ag it is a bit better, 50-50 atomic percent is closer to 65-35 weight percent. Hence, 16 Karat Au/Ag is 1/2 Au.

JQuinn

WIEGHT

Read the whole post. He said, "*If* one assumes that a karat is not a measure of weight". Oh, and he spelled "weight" correctly, too.

Don Kansas City

You could count the atoms.... for the ultimate measure.

One way to calculate the number of atoms is to use the atomic weight, Avogados number and then the WEIGHT of the substance added.

So, with effort one could then come up with the atomic fraction.

But, isn't weight about the easiest measure for a lumpy, perhaps powdered solid constituent/

You could melt it, and then measure the molten volume, somehoww, to eliminate the complexities of particle size and shape.

Or you could pour it into a graduated flask of water and wwatch to see how much water is displaced.

I highly recommend that you not begin this practice with Lithium, or Sodium,

This is turning into a weighty subject, trying to avoid weight.

In pure gold all atoms are gold atoms. So 24-karat gold is 100% atomic percent gold. Now the gold atom has an atomic weight, so weight can be a suitable measure. Now depending on its state (crystalline solid, liquid or gaseous) gold will have a molar volume, so volume can be a suitable measure. There is a connective between the two, because when one specifies weight one must say weight of how much: a milliliter, a teaspoon, a volume unit common in the precious metals trade, etc. As molar volume is the inverse of density (specific gravity) one feasible tool for the measurement would be the Jolly Balance.

The main problem with the volume approach for gold mixtures is that it is only for ideal solutions that the volume of mixing is zero, meaning you could add individual molar volumes to get the volume of the mixture. In some cases the deviation from ideality can be very small - examples would be where the second metal has the same crystal structure as gold. Both silver and gold are face centered cubic and the volume of mixing is small. The same could not be said for gold and aluminum, for example.

Let's get practical and have some common sense here, guys. Who's going to go to a jeweler and ask him to count the number of gold atoms and copper atoms so that you can know what the "karats" are?

Paul

Not quite sure what your converting weight to molar quantities has to do with the commonly used term of karat. And, if you really want to be scientific, John, it's not the weight that is used but the mass of gold and the atomic mass. Else you'd get different values on the moon.

Paul