Aqua Regia method with 12-13% Ag _inquart_

[giahylxag]

This can be good for the aqua regia digestions but there are a few things to keep in mind. First is the small holes in the top. For solutions and reactions that dissolve well, they are fine but for reactions where there are insolubles that need to be removed from the vessel that is a problem.

Let's start by discussing volume, based on the acid used to digest gold and gold alloys, a 12 liter has an effective operating volume of 7 to 7.5 liters. This depth leaves enough room for the solution to rise without risk of shooting out the condenser. (Yes I have seen that happen with overfilled vessels!) So a 12 liter flask will digest 50 ounces of the powder you get from first inquarting and parting in nitric. The flask is light enough to lift and pour the contents into the funnel to filter it. since the yield is 99%+ fine gold to start, your yield should be close to 50 ounces per reaction. Another spherical reactor standard size is 22 liter which can refine 100 ounces per load. Also small enough to lift and pour by hand. Both are also available with 4" conical heads which allow you to put your hand into the vessel once it is rinsed free of the acid to collect any diamonds that were in the gold. both sizes are available with both hard heat mantles and soft heat mantles.

Should I manually pour the liquid, or I suck the liquid (including the gold) by using a vaccum system?
In the previous test, I did it manually, most of the fume got sucked in the cone and to the fume scrubber, no problem. But then whenever I lifted the beaker, wether to pour the liquid out or add more chemical, fume leaked. The smell was not that bad, but sure not so good for long term health.
As you said: On closer look what I do not see is the hood exhaust. When a refining hood is set up the preferred method is to have 2 actual forms of exhaust. The first is considered fugitive emissions by the EPA. What that means is any fumes that escape your scrubber. That can be the fumes when you filter a solution or when you open and pour your acids or any other refining task. These fumes are minimal and with an acceptable flow rate passing through your hood they never cause an issue. But without that constant exhaust of air, those fumes will build up as you noticed.

For parting I would forego the heat band and place the pot on a large electric hot plate to get the heat from the bottom. My reason is 25% of the material you put in will not dissolve because it is gold, so heating from the bottom will likely penetrate the gold better during the process and result in higher purity. The funnel draws up into a fume scrubber and effectively exhausts the NOx. This setup was done without a hood because when the reaction stopped they let it cool and never handled hot acid. You will be decanting and rinsing and it will leak fumes. It should be done in a hood to keep the shop air much more liveable.

These pots come in many sizes typically 5 gallon but as high as 25 gallon. You need to consider 2 things. 1. how much you can easily lift. and 2. how much pure gold you want to refine in a single lot in a glass vessel. Matching the 2 volumes will make for efficient processing.

If you choose to start with a 12 liter vessel for aqua regia, a 5 gallon stainless pot should give you room to process 50 ounces of fine gold content inquarted 3:1 with silver. You should be able to inquart and part 2 lots a day and refine 2 lots a day in aqua regia. Maybe Mondays half that because you won't have a parted lot of powder to put up first thing in the morning. But I don't see a capacity of 450 fine ounces out of range per 5 day week for this system once you are comfortable with the process. I believe, without going back and looking, that is double of your weekly refining load which was 6 kg.

I will try with stanless steel pot, how many refine that a good pot can endure before it rust?
A stanless pot with a glass lift would be nice because I want to remotely monitor the process (by camera), I don't whan to be in the room the whole day. Cause there is not many things to do when the reaction is happening right?

 

[giahylxag]

I know we are not talking about chemical stone removal but if your typical customer is a jeweler who sets stones, it is a valuable service to provide for your customers. But if you cannot get your hand in the vessel it will not work. This is all I'll say about stone removal now but if it were me, and the local market has the potential for that type of work, I would be having at least one vessel with a 4" conical head. You can always start another thread to discuss this further if you decide to try it once you are up and operating.

High value stones like diamonds or natural stones are remove by hand.
Most of the stones from my scrap are synthetic stones. Value so little that I can throw them away.
Honestly I don't really know how to remove stones effectively using an induction furnance.
Traditional method that I know is melting stone jewlery by using a torch. Add some borax and let the stones stick to the borax.

 

[4metals]

I will try with stanless steel pot, how many refine that a good pot can endure before it rust?

A good quality stainless steel pot will last a long time. The nitric acid actually passivates the stainless so the acid will not attack it.

 

[autumnwillow]

The specific type of stainless steel you need is 304L.

 

[4metals]

The moderators would like to thank all of the members who contributed to the original thread that this post was based on, as well as those who asked questions showing what was missing. Because of the extra length and interest in this thread we have created the above, consolidated version making for an easier read. We encourage all members to read, comment, and ask questions in the original thread, Aqua regia method with 12-13% Silver HERE


The moderators have edited some posts in this thread that made reference to posts that were deleted. We strive to make these Library threads as concise as possible by deleting posts that do not add information to the original topic. All of the original posts are still preserved in the thread listed above.