I know that’s not quite how synthetic diamonds are actually made, but for the sake of this hypothetical: you have an unlimited amount of ordinary wood ash, and the magical ability to just squeeze it down to a diamond. How much ash do you need to use per carat?
I think first you’d have to extract only the pure carbon from the wood ash, or you’ll get something other than a diamond? Probably a blob of slag?
A carat is a measure of weight, so you’d need 200mg of pure carbon.
“a unit of weight for precious stones and pearls, now equivalent to 200 milligrams.”
Maybe throw in a little Boron to get a blue diamond.
I don’t know about wood, but supposedly the cremated remains of one person can produce up to fifty one-carat gems.
This depends very strongly on the quality of the ash, and to some extent the wood. Most of the carbon burned to CO2. The rest is largely in carbonates; calcium and potassium. This page does not give a direct carbon content figure, but it lists calcium as 29% (by weight) and potassium as 16% for pine burned at 600 C. By my math, that puts carbon at 11% by weight, counting just those two. Let’s round up to 15% to account for other carbonates, potash, etc.
So you need about 7 times as much ash as final diamond. 200 mg * 7 = 1.4 grams of ash. Of course, you need to extract the carbon to a pure form first.
If you want to stretch the definition of “ash”, we can include charcoal (which is after all the solid byproduct of burning wood in a particular way). Charcoal may be up to ~80% elemental carbon, so you need barely more than the final weight.
As I understand the question, you want to know how much wood charcoal is needed to make a carat of diamond (assuming that is possible.) Ash from a wood fire should have little or no carbon left, so you’re even farther from producing diamond than with charcoal.
When you burn diamond, all the carbon becomes CO2 and you get practically no ash.
Okay, I didn’t know that. I guess I am asking about charcoal, then.
Even charcoal, as mentioned above, is at best 80 percent carbon–which would result in a very poor quality diamond. Definitely not gem quality, maybe not even drill-bit quality. Probably look something like carbonado
(Superman III–not a documentary.)
Some portion of wood ash consists of potassium carbonate & calcium carbonate (as noted by Dr. Strangelove), so it’s not strictly true that a wood fire leaves behind no carbon. That said, high-quality charcoal has a lot more carbon in it than wood, and combusting it leaves behind very little ash; so you’re definitely better off trying to make diamonds out of charcoal than out of the ash it leaves behind.
In fact, the cremation should produce white ashes, and have no carbonate at all.
The issue is that the recently cooked and powderised calcium phosphate will be able to absorb CO2 and so contain carbon atoms. So it depends on the precise treatment during and after cremation as to how much Carbonate and CO2 is in the ashes, but its not meant to be much, and it won’t be the persons original Carbon, it will be carbon from CO2 in the air.
Ooh, now that would be one swanky campfire.
“Man, it costs a fortune to heat this place.” (Sylvester Stallone in Cliffhanger, as he throws another handful of $10,000 bills on the fire.)