i need to devise a method to seperate grains of gold from grains of quartz sand by using the differnce in specific gravity between gold and quartz.
2006-12-08 16:51:15 · 4 answers · asked by Super 5 in Science & Mathematics ➔ Earth Sciences & Geology
Find a liquid that has a specific gravity somewhere between gold and quartz. Then the gold will sink and the quartz will float.
One such liquid is mercury but it has the added property that it amalgamates with the gold so then you would have to separate the gold from the mercury. This can be done by heating and causing the mercury to evaporate. This is not something to be done casually since mercury is poisonous.
2006-12-08 17:27:08 · answer #1 · answered by rethinker 5 · 1⤊ 0⤋
The "old prospector" above me is right -- basic gold panning relies on the fact that gold is MUCH denser (has much higher specific gravity) than water so it stays sunk well to the bottom of the pan while you slosh the water around in it, but the quartz is only slightly more dense than the water so is much more easily washed away by the water's movement.
Sluices also work on the same principal -- water flows over a mixture of gold and sand/quartz, and over a corrugated "washboard" type surface. The gold sinks into the valleys while the other stuff is carried by the water up and over and eventually washed away.
However, there is a more direct solution -- the sort of thing rethinker is suggesting:
Quartz has a density (specific gravity) of 2.67 grams per milliliter, while gold has a density of 19.3 grams per milliliter. If you could find a liquid that is between these two values, the gold would sink in it and the quartz would float on it.
There is such a liquid -- it is called bromoform, a.k.a. tribromomethane. Quartz will just barely float in it while gold will sink quite well. You would want to be wearing protective gear while working with the stuff though as it is kind of nasty. But it is a great "thinking outside the box" type of solution for a classroom! It used to be used in geological assaying, I don''t know if it still is or not (Hawley's Condensed Chemical Dictionary, 11th edition, 1987).
2006-12-09 01:28:36 · answer #2 · answered by Mustela Frenata 5 · 1⤊ 0⤋
Old prospector is right. Panning is the right and cheapest method. Only you need to practise a lot - it took me more that 3 months to be a reasonably successful panner. And another problem is that you will never be able to separate all the gold present in the mixture - some coated gold, flour gold etc. will be missed.
I would not suggest you to use mercury. Although it amalgamates all the gold and it is easy to separate again (just by heating), the mercury vapour is a bit too hazardous. If inhaled, it may be fatal even. Bromoform is a better choice. Bromoform separation is still extensively used in petrology labs for manual grain size analysis, and can be used in your case.
2006-12-09 13:34:45 · answer #3 · answered by saudipta c 5 · 1⤊ 0⤋
This old prospector is appalled that you don't know about panning.
2006-12-09 00:53:38 · answer #4 · answered by Pseudo Obscure 6 · 1⤊ 2⤋