# When and what is the best way to filter aqua regia?



## firedan525 (Apr 28, 2007)

Hello all. I am new to gold scrapping and refining. Being a firefighter I have alot of time off. I started investing in gold bullion and I came across refining and scrapping. This made alot of sense and seemed very intresting. Now I have a great source of gold pins, cpus, fingers for very cheap. NOW I'M HOOKED. I bought ishor's aqua regia products. Subzero (nitric acid substitute), Storm Gold percipitant, gold purity test drops, test for dissolved gold. I did my first batch but didnt take my time nor did I get any advice and I completly screwed up that batch. Learning my lesson I, I have a few questions for you more experienced w/ aqua regia. What's the best containers to use. What is the best way to decant my solution w/o disturbing the gold sediment after percipitating? Can excess urea affect the way gold percipitates? How do I filter my aqua regia acid, and do I use urea before Filtering? Can coffee filters be utilized. Thankyou very much and any thing I may need to know just post it on this forum.


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## Noxx (Apr 28, 2007)

Hello,
If I was you, I would add urea before filtering. This way, acid has been neutralised. But you can do both. Coffee filters will work perfectly.

Use platic buckets or pyrex vessel if you have more budjet.

Let it settle overnight then carefully pour the liquid. The gold should stay at the bottom.

Excess urea won't affect a thing unless you put a way too much ! Stop adding urea when it doesn't fizzle anymore.

I hope it helps


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## Harold_V (Apr 28, 2007)

An excellent way to decant solutions is to use a small length of vinyl hose. I preferred 1/2" OD hose with a 1/16" wall. Make the hose length long enough that it is slightly more than double the depth of your deepest container. Start with one that's too long, and trim it until you're happy after you've used it a few times. A hose that is too long is difficult to control, and serves no purpose aside from annoying you no end.

To get the solution flowing, all you have to do is fill it with water, holding the hose level, with the ends up. Once it's full, cover the end that will be the discharge (use your gloved finger) and lower it so the opposite end is higher. Move to your container that you wish to empty, and carefully place the open end inside, in the solution. Now raise the opposite end, the one that is the discharge side, so it's just slightly lower than the intake end. At this point, if you keep the discharge side below the pickup side, solution will begin to transfer when you remove your finger----all you have to do is follow the solution down the intake side, insuring that the hose never picks up air, and keep the discharge side lower than the intake side at all times. 

How low you hold the discharge side determines how fast the solution transfers. Armed with this idea, I think you can see that if you work carefully, you can slow way down as the solution nears the gold, so you don't pick up any of it in the hose. It stands to reason that it's important that you be able to see the contents. This system isn't quite as successful with opaque solutions----you have to work blindly. 

In order for this to work, you must be able to place your vessels at different elevations. A laundry sink works perfectly well for height differential, if you happen to have one at your disposal. I installed one in my lab expressly for that purpose. 

Accidents are bound to happen. Always transfer your solutions to a second vessel, not a drain. That way, if you happen to pick up values, they'll be waiting for you in the second vessel. 

Pouring from a beaker, or other container, that contains values is a terrible idea. You'll come to understand that whey you have your first unhappy ending. I recommend that you never pour from a container unless there is nothing of value involved. 

Harold


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## goldsilverpro (Apr 28, 2007)

Hi, firedan. Good to have you aboard. Most all of your questions have been answered elsewhere on the forum but, the info is spread out and is often hard to find. Use the search function for best results.



> I bought ishor's aqua regia products. Subzero (nitric acid substitute), Storm Gold percipitant,



It's becoming common knowledge that Storm is sodium metabisulfite and Subzero is sodium nitrate. Here's a guy on eBay selling them for much less money.
http://stores.ebay.com/Pacific-Resources

I prefer sodium sulfite. Here is a recent post I made about it:
http://goldrefiningforum.com/phpBB3/viewtopic.php?t=349&highlight=sodium+sulfite

Good questions. Anyone answering these questions will give different answers. Everyone develops their own system, depending on their own conditions, equipment, etc. One method is not necessarily the best, Try to pool everyone's ideas together and find the way that suits you. Keep in mind, however, the goals: don't lose any gold; do things to get maximum purity; think safety. Here's the way I do it.



> What's the best containers to use.


I prefer 4 liter beakers for dissolving and use a watch glass to cover it. In case of breakage or spillage, I place the beaker in a 5 quart, white, flat bottomed, Corning Ware dish and put the dish on the hotplate. For 5 ozs, or less, you can use a pyrex, 10 or 12 cup, replacement drip coffee pot. The best is the one with a stainless steel ring holding the short plastic handle, only at the top. Don't get the type where the bottom of the handle is attached. It will burn.

After dissolving, I transfer the solution to a clean, white, 5 gallon plastic bucket. I add 3 times the volume of tap water that I have acid plus about 60 mL of battery acid per each gallon of acid. These two additions will drop out any silver or lead that is dissolved in the acid and these will be removed by filtering. Stir the solution. The long straight part from a plastic clothes hanger works great.

I sit the bucket on a table or a bench. I place a piece of 2" X 4" underneath the back edge of the bucket. This tilts the bucket towards you and allows the solids to settle in one spot on the front bottom of the bucket. I put the lid of the bucket and allow the solids to settle overnight,



> What is the best way to decant my solution w/o disturbing the gold sediment after percipitating?


There are three ways to do this. I do all three, depending on what I'm dealing with. More often than not, I siphon. No matter which one I use, I always end up filtering the entire solution. Super clean solutions, before precipitating, is necessary for good gold purity. This goes fast, however, if you first use one of these methods to get a gross separation of the liquid and the solids. Decant, dip, or siphon off the liquid. Filter the liquid first and then filter the solids plus the remaining liquid last. If you were to try and filter the entire thing, without first separating the liquid and solids, it would take forever.

*(1) Decanting.* You can carefully pour off the solution into another bucket. This is the fastest way. When you tilted the bucket, the solids settled together in one pile. Before pouring, put the receiving bucket inside a plastic tray with about a 7 gallon capacity (WalMart), to catch drips and spills. Put the tray on the floor. When you pour, keep the pile nearest the bucket you are pouring into. In other words, try not to disturb the pile. Go slow and steady. Keep an eye on the solids. Just before the solids start to go over, stop. After pouring, there will be a slight film of solution, where you poured from, at the rim of the bucket. Either have a friend rinse this gold bearing film into the receiving bucket or, rinse it back into the bucket containing the solids. If there are drips remaining anywhere on the outside of the bucket, wipe them off with a piece of paper towel. Save this and any other paper towels you've used to wipe up spills that contain PM's. Eventually, you can burn the towels and recover the values. It's actually better to have 3 separate buckets to save PM laden towels - gold, silver, and Pt group.

*(2) Dipping.* I don't use this method much when working with buckets. I use it a lot when working with open plastic drums. Often, it is difficult to raise a heavy drum high enough to completely siphon it. So, I keep it on the floor and siphon it into an empty plastic drum sitting next to it. When half of the solution is siphoned, the solution level in the 2 drums will be equal, and, therefore, the siphon will stop working. I dip the other half of the solution out with a neat scoop that I cut from 1 gallon plastic jugs. 

With the bucket still tilted, carefully dip the solution out, and into the filter, with a 1 cup Pyrex measuring cup - the type with a handle. To keep from disturbing the solids, use this technique. Turn the cup sideways and slowly immerse it part way. As it fills, slowly turn it upright and, at the same time, bring it out of the solution. If you do it right, the solution surface will hardly make a ripple. As you get near the bottom, you have to be more careful and fill the cup less and less each time. To keep from dripping solution all over, hold a bucket lid under the cup, with the other hand, when moving the solution to the filter. When safely over the filter, remove the bucket lid. When finished, rinse off the lid and the cup into the filter. When the liquid is completely finished filtering, start filtering the solids. 

*(3) Siphoning.* Proper siphoning can remove the most liquid without disturbing the solids. This makes the filtering go faster because there are less solids to filter. And, the solids are what clogs the paper and slows down the filtering. I don't use gloves when siphoning because the tubing is harder to manipulate. Of, course, I always have purple hands. I do recommend that you use gloves. The thinner the gloves, the better, for this operation. Practice the siphoning a few times to get the hang of it. Put a little sand in a bucket of water. Tilt the bucket, let the sand settle, and siphon off the water.

This is a little harder to explain without pictures. Put a clean bucket inside a plastic tray and put the tray on the floor beneath the tilted bucket on the bench. Get about a 4' length of 3/8" ID clear, flexible, plastic tubing from the hardware store. With this size tubing, a full bucket will take about 5 minutes to siphon. 

These instructions are for a right handed person. Reverse them if you are left handed. Fold the tubing double so that the ends meet and are together. Fill the tubing with water to the brims of both ends of the tubing. Stand on the right side of the buckets. Hold the ends of the tubing together in your left hand. Keeping the ends at the same level, hold the right end in your right hand and put your left index finger over the left end, to seal it. Keeping the left end sealed, lower it to the bucket on the floor, until your hand is partway inside the bucket. And, here's the tricky part. At almost the same time, put the right end about an inch into the solution and release your left index finger. Actually. the left finger release should occur about a half second after you stick the right end into the solution. If the solution flows, release the left hand completely and allow the tubing to hang in the lower bucket. If it doesn't flow, start over.


As you're siphoning keep an eye glued to the end of the tubing that's in the liquid. Try to keep the tubing only about an inch deep in the liquid. This is hard to see if the liquid is dark colored. I usually color about 1-1/2" (measure it) of the end of the tubing with a red Magic Marker. Black is OK but you can see the red better. This enables you to determine how deep the tubing is in the liquid. The marker will wear off after a few times and you will have to redo it. It's hard to hold the tubing steady and keep from disturbing the solids. To remedy this, I put the very edge of the tip of the tubing against the front side of the bucket, while keeping it about an inch deep. As the liquid level goes down, slide the tip down with it, against the side of the bucket. As you approach the solids, reduce the depth of the tip in the liquid and, with your left hand, slowly tilt the bucket a little more towards you. . 

I repeat, keep your eyes on the tubing. If the tubing comes out of the liquid, for only an instant, the siphon will break and you'll have to start over. After siphoning, rinse the tubing, inside and out, into the top bucket along with the solids. The best thing to use for rinsing and, for filling the siphon tubing with water, is a lab type, plastic, squeeze type, squirt bottle with a long spout. The spout points sideways from the lid. I have also seen these in sporting goods stores. Joggers use them.



> Can excess urea affect the way gold percipitates?



With no urea, the Storm (sodium metabisulfite) reacts with the excess nitric before it starts dropping out the gold. With too little urea, the same thing happens. If you don't have any excess nitric to start with, you don't need urea. That is my approach and I've covered how to do it on several other threads. With a lot of extra nitric and no urea, you may have to add several pounds of Storm before anything happens. With way too much urea, the excess will sit on the bottom and won't dissolve.



> How do I filter my aqua regia acid.....Can coffee filters be utilized


There is a good discussion of filtering on several threads and this thread, especially. With coffee filters, lazersteve's setup would be best. With lab type filter papers, mine would probably be better.
http://goldrefiningforum.com/phpBB3/viewtopic.php?t=251



> do I use urea before Filtering?


Interesting question. I don't use urea any more and haven't really thought about this question. Either way would work, although most people do it after filtering. However, if you are heavy handed, add an excess, and have undissolved urea sitting on the bottom, it would be better to filter after adding. Of course, how do you know in advance that you will add too much urea? Were I to start using it, I would probably add it before filtering.


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