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Hi Steve: Thank You.

I have gone to your site, but unfortunately I am still running Windows 98se. (don`t like XP. eventually I guess I`ll be forced into it.) Media player 11 doesn`t support 98se.

On the HCl- Cu-Peroxide process, I have used this successfully many times, already, to dissolve the base metals and leave the gold intact. I just use enough peroxide to start the process and as the Cupric in solution builds up, just enough peroxide to remove the Cuprous. The HCl is only about 2-4 molar. My solution is heated to near boiling and this works on a batch of unpopulated pc boards in about an 30-60 minutes. Basically its a Copper leach and anything below Copper in the EMF series should not be dissolved.

Some Gold does dissolve, because of the peroxide, but I believe I have recovered most of it it by cooling my excess solutions to room temp. and adding a small amount of Zinc. All I see is traces anyway. There`s a Patent online that describes this similar recovery method and his work shows around 95-99% recovery.

What I don`t know is were Palladium lies in the EMF series, If its below Copper, it shouldn`t dissolve. My Chemistry books don`t list it. I`m going to try to Google it now.

Al
 
Irons,

I agree with you totally in the dangers that these chemicals possess. This forum greatly profits from your reminders of the dangers involved. I, for one, appreciate these reminders and learn from them.

However, I see my function in another light. Almost everything on this forum is dangerous and potentially polluting, if you don't know what you're doing. I see, as one of my jobs, keeping people safe and legal, no matter what they're doing. I also want to spell out every option available. I do 100% advise against, and won't discuss, the use of such things as mercury, HF, or combinations that can create explosions. One day, when I give my treatise on the wonderful selective cyanide stripping of gold plating, you'll probably go ballistic. Just joking, kinda.

You can read my posts and find nowhere that I advocated the use of chromic acid. Quite the contrary. I said it was the most dangerous chemical combination I had ever used. But, I don't agree that just mentioning something advocates it. If anyone has clipped Pd points and is thinking about trying the chromic acid, I will post the complete safety, handling, dangers, waste, and usage instructions, in great detail, as I know them. All one needs to do is ask. A trick, as in all setups, is to always start small - 200 to 300 mLs, in this case? Learn before leaping. Don't get it on your skin, don't breathe the fumes, and don't eat it. Your set up and technique must protect against these things.

A problem with chromic acid usage is the waste. You might convert it from the hexavalent to the much less toxic trivalent form, although all of that sulfuric might not allow the conversion. Chromic acid might precipitate out if you could evaporate all of the water off of the H2SO4/chromic. But, no matter what you do, you still have toxic waste that has to be legally disposed of - but probably only slightly more critical than the common heavy metals acid wastes being generated by all.

And, finally, there are probably other more genteel ways to selectively dissolve the copper without hitting the palladium. When I found the H2SO4/Chromic acid, I stopped researching - it worked so damned well. You probably could substitute potassium or sodium dichromate for the chromic acid. It's on Ebay:
http://tinyurl.com/2v85kr

Looking back, the inherent dangers and the subsequent conquering of them, is one of the things that attracts me to this profession. I'm a "green" refiner, also.
 
The chart on my website comes from a Viginia Tech science website.

I've seen one other detailed chart, but I can't seem to locate it at this time.

Steve
 
Yea, chromium compounds have fallen out of favor. Time was when glassware was cleaned with chromic acid. CrO3 is nasty stuff indeed, not just from the toxicity and carcinogenic standpoint either; it's very aggressive towards organics, hence its use as a cleaning agent. Nowadays, ammonium persulfate in sulfuric is used for cleaning, while CrO3 and dichromate really only for plating. Regular chromate is used for the yellow line on roads. AFAIK, it's only the +6 valence that's truly nasty.


GSP, I'd like to hear more about the cyanide stripping process. Cyanide is easy to work with and very easy to dispose of (bleach).

I agree though, leave HF alone, I hate working with it, it makes me paranoid.


It's all how you use it.
 
Steve, I also found it in Google books, just above Gold.

Ok, since GSP pointed out the Palladium points from relays are considered pure, my idea is to use the Copper leach on cut off Palladium points. The Palladium should not dissolve, while any attached base metals will.

Then, on other materials where Palladium is alloyed with Silver or solders or those mono caps use the AP method or Nitric acid.


Jim is concerned about what to do with the dissolved Palladium and Silver in solution. Precip the Silver first as you described, then I believe the reagent of choice would be Sodium Chlorate to precip Palladium.

Hey, if I could suggest, on your website allow Real player to be used along with Media player. Real Player supports Win95 & 98 and plays anything Media Player can!

Al
 
GSP, I'd like to hear more about the cyanide stripping process. Cyanide is easy to work with and very easy to dispose of (bleach).
Click to expand...



Chris has mentioned the topic several times but not really in depth.
I would be interested myself.
 
Lou said:
Yea, chromium compounds have fallen out of favor. Time was when glassware was cleaned with chromic acid. CrO3 is nasty stuff indeed, not just from the toxicity and carcinogenic standpoint either; it's very aggressive towards organics, hence its use as a cleaning agent. Nowadays, ammonium persulfate in sulfuric is used for cleaning, while CrO3 and dichromate really only for plating. Regular chromate is used for the yellow line on roads. AFAIK, it's only the +6 valence that's truly nasty.


GSP, I'd like to hear more about the cyanide stripping process. Cyanide is easy to work with and very easy to dispose of (bleach).

I agree though, leave HF alone, I hate working with it, it makes me paranoid.


It's all how you use it.
Click to expand...

When I began to take Chemistry classes back in the early 60's, Chromic acid was the standard procedure to clean all lab glassware. It makes me cringe to think about all of it we flushed down the drain.
I'm not trying to get on anybodys' case about process or procedures. I'm still surprised I made it this far. My first week of classes, I took a 500 ml beaker and filled it with Sodium chips, then walked over to the sink and filled it with water. That was my first lesson in not to mix thing you can't get away from before they go off.
 
eagle2 said:
Irons, you cracked me up! :lol:

Where in the world was the instructor?
Click to expand...

This is what happens when you leave a 20 pound block of Sodium Metal under a bell jar, sitting next to a sink on the classroom lecture table and beakers within arms reach, then walk out of the lecture room, leaving a bunch of crazy newbies alone.
 
I am not sure on this one....just asking. But, isn't it true, that some (if not all) of the palladium will be precipitated when adding sodium chloride to a mixture of silver and palladium in nitric?

Also, I believe, that the sodium chlorate will only work to drop palladium from nitric....after.....amonium chloride is added first. Yes?
Randy
 
Randy said:
I am not sure on this one....just asking. But, isn't it true, that some (if not all) of the palladium will be precipitated when adding sodium chloride to a mixture of silver and palladium in nitric?
Click to expand...

I think that only the silver chloride will precipitate. Some Palladium may be dragged down with the silver.

Randy said:
Also, I believe, that the sodium chlorate will only work to drop palladium from nitric....after.....ammonium chloride is added first
Click to expand...

Correct. The solution will also need to be warm, nitric free, and concentrated.

Steve
 
Yes.

Before precipitation of precious metals from solutions contianing nitric acid you will need to evaporate the solution down until nearly dry. Do not completely dry out the solution.

After evaportion add some HCl to convert the nitrates to chlorides and repeat this process three times or until no more nitric (brown) fumes are evolved.

Using this method on auric chloride solutions eliminates the need to use urea after dissolving Gold with AR. If you dissolve your Gold with HCl-Cl this step is not necessary.

If you dissolve your Palladium with AP this step is not necessary, but concentration of the solution is still required.

Steve
 
And you wonder why your metals won't precipitate according to theory...

Lou can pipe in on this because he's familiar with using Palladium as a catalyst.

http://tinyurl.com/2ojl2p

As regards hydrogen, it is to be remarked that the general
behaviour of that element shows that it must be looked on
as a metal, especially as large quantities of it can be taken
up by certain metals, particularly by palladium,* and the
products of these actions behave like alloys. Now, if a
small plate of palladium is saturated, electrolytically, with
hydrogen, and is then immersed in a solution of copper
sulphate, the plate is very soon covered with a lustrous
layer of copper. In a similar way, gold, platinum, silver,
and mercury are precipitated ; but lead, iron, cadmium, zinc,
and magnesium are not precipitated.
The following facts are in accordance with these observations :
metals of the lead, iron, etc., class dissolve in acids with,
evolution of hydrogen, whereas metals of the class which
contains gold, platinum, etc., do not evolve hydrogen from,
acids (overlooking such secondary reactions as those which
occur with nitric acid). Hence the value of the solution-
pressure of hydrogen occluded by palladium must lie between
those of the solution-pressures of copper and lead. Experiments
with a palladium-hydrogen plate and a normal
sulphuric acid solution, at 17°, showed a difference of
potential equal to — -26 volt, putting the potential of the *
Palladium is capable of occluding 936 times its own volume of
hydrogen.
 
Irons.

I hate to be a jerk, but could you please shorten that link? You can use tinyurl.com or the way spelled out here - see Steve's post:
http://goldrefiningforum.com/phpBB3/viewtopic.php?t=368

I spent 3 years near Caribou, ME. Where are you located? I loved it up there and hope to re-visit that area some day. The land of Maine-iacs.
 
Jim:

Steve wrote:

think that only the silver chloride will precipitate. Some Palladium may be dragged down with the silver.


I handle co-precipitation by redissolving the precip. In the case of Silver Chloride, dissolve it in Ammonia and separate the traces. Then precip the AGCl again, with just enough HCl. Do this right away, don`t delay (there`s the possibility of forming a fulminate)!

Incidentally you will be purifying the silver. You will get rid of a lot of Copper, Lead, Arsenic, Silica, etc.

Co-precip. is a problem all refiners face. In Gold solutions with a lot of Iron in solution I find its best to get rid of it, first, by gradually increasing the PH to 3-4. This also drags down some gold, so I reprecip the Iron Hydroxide too. The problem is worst in concentrated solutions.

When You read some Chemistry Book or Paper describing how to precipitate something, you will mostly see them working in a beautiful pure solution, containing only one metal in solution, then they add their wonderful reagent and come up with perfect results.

We are working with a mess of base junk in solution, So don`t expect perfect results. Do the best you can and experience will make a big difference.

Al
 
eagle2 said:
We are working with a mess of base junk in solution, So don`t expect perfect results. Do the best you can and experience will make a big difference.

Al
Click to expand...

My experience in refining even relatively clean gold, a product of processing by the inquartation method, was that the quality of my gold was always questionable. As a result, I started re-refining my yields on a regular basis. The second precipitation, along with what I consider to be good washing procedure, yielded gold of exceptional quality.

It's unreasonable to expect gold of high quality when it comes from dirty solutions. Drag down is a problem, and not always addressed well by extended washing alone.

Harold
 

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