Probem Dry heat Gold Aqua Rigia solution to get all 18k gold

[Pareshthesia]

Hello friends pls help me I am Jeweller and my aim is to remove stones like Diamonds ruby suffire emerald from studded 18k gold scrap I prepare Fresh Aqua Rigia 3:1 ratio resolve the gold then filter the stones and the dry heat the solution in Pyrex glass vessel over a hot plate so that I get gold in better purity but when I check the ratio with 18k gold that I originally dissolved I loss some gold does the gold evaporate with the acid I take care that the solution particles don't boil so that I lose the valueable gold particles I scrap all the gold carefully and add a little water to the container and with tissue wipe all the gold and place in the crucible In following formate first i place the powder mixed with backing soda and Some kind of salt then place the tissue with which I viped gold and then say some solid gold on top of it and then place in fernes to heat it . Now my problem is I am having gold loss like origal weight 143.500 of 750 purity and procesed gold 132.600 gms of 786 purity which is 138.650 gms of 750 Lose of 4.850gms why is this so pls help if anyone knows a better and faster process

 

[nickvc]

I must admit I couldn't fully follow your processes but I think that your evaporating your gold chloride down to crystals and then melting them. If you have dissolved all your metal I would use a precipitant and recover your gold as fine gold, there are several choices of precipitants depending on where you are in the world. The melting of the crystals could be the source of your losses as I think they would vaporise in the furnace if not covered, the clever chemists on the forum will correct me if I'm wrong The other thoughts I have are what weight of stones are you recovering,have you allowed for them in your calculations? Stone set jewellery that's been worn is usually caked in dirt behind the settings so put them in your ultrasonic and then dry them before weighing them to calculate your gold content. The other possibility is that your starting material isn't as marked,not actually 750 that's not uncommon.

 

[butcher]

Chlorine gas can evaporate off gold at roasting temperature.
Research forum you will find a lot to help you.