# How to Calculate the exact amount of Gold reagent



## rohaneha (Aug 2, 2011)

Hi guys.. well i have a problem to discuss with you. i add hydrazine hydrate to precipitate gold. I could not judge how much of hydrazine hydrate should be used to precipitate the aqua regia solution. is there any calculation to know the exact amount of hydrazine hydrate for the AR containing filing scrap weighing 450gms of Gold(92melt)? i generally add 250ml of Hydrazine hydrate solution, but still i fell short by 15 gms in fineness. what could be the reason? I do certain things which, i think is not necessary but i still want to describe. I usually add 2 teaspoon of salt and some 5 - 6 gms of copper and heat it. And also add urea into the solution before filtering it. Is this where i make mistake?


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## butcher (Aug 4, 2011)

if you have the equation of the chemical formula, you can calculate the grams per mole of each ingrediant, using some math and the periodic chart.
but when done in reality usually a slight excess reagent is used.

and you would need to know how much gold was in solution.

karat gold can can be marked 14K even if it is only 13.5 K,
I do not know if this will help.


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## jimdoc (Aug 4, 2011)

Doesn't hydrazine precipitate all metals out of a solution?

Jim


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## goldsilverpro (Aug 5, 2011)

rohaneha said:


> Hi guys.. well i have a problem to discuss with you. i add hydrazine hydrate to precipitate gold. I could not judge how much of hydrazine hydrate should be used to precipitate the aqua regia solution. is there any calculation to know the exact amount of hydrazine hydrate for the AR containing filing scrap weighing 450gms of Gold(92melt)? i generally add 250ml of Hydrazine hydrate solution, but still i fell short by 15 gms in fineness. what could be the reason? I do certain things which, i think is not necessary but i still want to describe. I usually add 2 teaspoon of salt and some 5 - 6 gms of copper and heat it. And also add urea into the solution before filtering it. Is this where i make mistake?


I don't understand some things. What is 92 melt - 22K, I would guess? Why and when do you add salt and copper? That makes no sense at all to me. Same with urea?

I would think you don't need anything but hydrazine hydrate and stannous chloride (to test the solution to make sure all the gold has precipitated). If the stannous chloride tests negative and shows no gold in solution, you know you have collected it all. Therefore, what you got is what was there. If it tests positive, add a little more hydrazine hydrate, allow it to react, and then test again. Base everything on the stannous chloride test rather than how much hydrazine hydrate you have used. When I used hydrazine sulfate to drop gold, there was no way to predict exactly how much it would take.

Jimdoc may be right, under certain conditions. Gold dropped with hydrazine is often not as pure as when using a sulfite instead, such as SMB or sodium sulfite. The problem with these is that you must eliminate any (or, most) free nitric before using them, whereas, with the hydrazine hydrate, that is not usually necessary. There are several ways to eliminate nitric, all of which are described in detail on this forum. The best approach, however, is to not add more nitric than is needed to dissolve the gold. That way, there is no excess nitric to eliminate. That is my approach and I have explained how to do this, in detail, several times on the forum.


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## bhupesh17 (Aug 17, 2011)

hi,i m bhupesh mulik frm mumbai,india
generally i make 500ml hydrazine hydrate+4500 ml water solution.then i add slowly few quantity of HH+h2o solution to gold dissolved aquaregia solution.i had seen black colour on the surface with stirring(slowly)and when i saw a white salt start precipitating on surface,i will stop adding HH,


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