# Cleaning precipitated gold powder



## Renaldas (Dec 18, 2010)

I read advices to boil precipitated gold powder in hydrochloric, nitric, sulfuric acid, wash with ammonia and use more substances. What do you think about boiling precipitated gold powder boiling in HCl, where several drops of nitric are added (such a very weak AR)? 
Till this moment I boiled the powder in HCl, but after some thinking decided, that very weak AR is better to use, as HCl, because HCl have no deal with copper, palladium, platinum and much more materials, which could be captured precipitating gold from not very clean solutions.
What do you think about this?


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## Barren Realms 007 (Dec 18, 2010)

Not a very good idea. Follow the washing procedures laid out in the forum.

3 Boils in water
3 boils in HCL
3 boils in water
3 boils in ammonia
3 boils in water
3 boils in nitric
3 boils in water

And don't forget about your incineration during the process.

then refine your 2nd time= pure, pure gold


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## philddreamer (Dec 18, 2010)

My personal opinion, after practicing what I've learned here, is never to add nitric after going to the "trouble" of getting rid of it. You would be dissolving some of the gold again, & now you'll have to drop again; to add more nitric on & on & on. 

After AR reaction is over, most of the silver would be on the bottom; now I add some sulphuric to the solution so any lead in the solution drops. Filter the solution & drop with SBM. Wash as recommended, 3 boils in water; 3 boils in HCL; finally 3 0r 4 boils in water & dry. I see the difference in how much lighter the color of my gold got. (A wash in ammonia, added to this, if you suspect ag still in the gold powder.)
I learned here that HCL DOES deal with copper, that's why its use for the wash; & most of your PGM's should still be in solution to be dropped...

pHIL


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## lazersteve (Dec 18, 2010)

I agree with Phil, no nitric.

I use three hot water rinses-settle-siphon, then 1 boil in HCl-settle-siphon-test liquid with stannous, then three more hot water rinses-settle-siphon-dry. Refine a second time in AR-cool with ice-filter clear and repeat wash cycles.

Steve


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## samuel-a (Dec 18, 2010)

precipitated gold have some impurities that mechanically dragged down with it, and they will be gone after HCL boil.

gold powder do not act as melted piece, and even might dissolved in HCL boil, test it next time you wash gold with HCL.

always test acid washes


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## Anonymous (Dec 18, 2010)

samuel-a said:


> gold powder do not act as melted piece, and even might dissolved in HCL boil, test it next time you wash gold with HCL.
> 
> always test acid washes


If you have completely neutralized,expelled,or used up,all of the nitrates in the AR then there should be no problems with gold being digested with a clean Hcl boil.
I have never had a wash come back positive,unless there was a mistake on my part before I started washing.


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## samuel-a (Dec 18, 2010)

mic

I'm referring to only minute traces of gold, probably nano-scale particles.

i do wash properly with water before HCL boil, and still it is faint positive color.
To proof that, I've tested different levels of contaminated dropped gold that have been washed well with water, and it seems, that the dirty the drop is, the more tendency of the gold show up as well in the test...
can't explain it though....


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## Oz (Dec 18, 2010)

I have said this before, always test your washes and rinses, plain HCl can digest gold. As part of my gold refining routine I take my once refined gold powder (after washing) and place it on a hot stir plate in HCl to re-digest it for precipitating a second time.


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## Anonymous (Dec 18, 2010)

Oz said:


> plain HCl can digest gold. As part of my gold refining routine I take my once refined gold powder (after washing) and place it on a hot stir plate in HCl to re-digest it for precipitating a second time.


In 6 years I have never once seen common muriatic acid digest refined gold,whether its boiling or not.
Do we need to rewrite Hoke and the forum handbook?


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## samuel-a (Dec 18, 2010)

mic said:


> Do we need to rewrite Hoke and the forum handbook?



maybe... 8)

Edit:

here is the stannous test of the HCL washes from my last inquaration :



it's hard to tell by the picture, but trust me, this is purple, and the powder washed well with platy of water.


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## Anonymous (Dec 18, 2010)

Considering my personal experience and the experience of others I know,and the forum handbook,and Hokes,which all contributing members swear by,I think I stick with what I know.No offense.


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## Anonymous (Dec 18, 2010)

samuel-a said:


> it's hard to tell by the picture, but trust me, this is purple, and the powder washed well with platy of water.


Then you still had residual nitrates on your powder.This is why harold preaches to incinerate.You can wash it with boiling water a thousand times and still have residual nitrates.


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## qst42know (Dec 18, 2010)

Certainly worth a stannous test.

I have experienced positive tests in the HCL rinse. Powders from dirty solutions being the worst offenders. I wouldn't recommend skipping the rinse by any means, just know it needs to be saved, perhaps used in the next AR batch.


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## Anonymous (Dec 18, 2010)

qst42know said:


> Certainly worth a stannous test.


I agree whole heartedly.
but as I stated before I have never experienced a positive result unless it was my fault.


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## Platdigger (Dec 18, 2010)

Even still, can't you see how that using the method Oz does would save a few steps, time, and chemicals?
Notice he said with a stir plate. That means he probably has a stir bar.
Well, actually I know he does. The rapid stirring must introduce enough oxygen from the air to oxidize the gold.


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## qst42know (Dec 18, 2010)

Whip in some air to make oxygenated HCL?


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## Platdigger (Dec 18, 2010)

looks like


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## Anonymous (Dec 18, 2010)

Actually we have had this exact conversation before,and you may be correct about the stir bar,though I highly doubt it introduces that much oxygen,however it does not have any bearing on the former conversation.


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## Barren Realms 007 (Dec 18, 2010)

Could be using tap water with chlorine in it.. :!: :?: :arrow:


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## Platdigger (Dec 18, 2010)

Mic, why do you doubt him (Oz)?
The guy does more refining than you may realize.
You should try it. I don't have a sutible stir bar at the moment.

If you are worried about straying from the original posters question we could delete all the posts after Steves. 
He gives his method and He mentions testing the washes.


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## Anonymous (Dec 18, 2010)

Thanks but the old saying "if its not broke,don't fix it"works for me.
I have no problems with the way I process.If that works for him,and it must or else he wouldn't do it, then that is great.This is about Hcl dissolving/not dissolving gold,not superoxygenated Hcl.


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## Oz (Dec 19, 2010)

Mic,

You are absolutely correct, if what you are doing works for you there is no reason to change it. 

Now let me explain why I said what I did. As you have pointed out, most anyone you talk to, or any respected book or reference on refining says that HCl alone will not digest gold. Because of this many people when washing gold in HCl will toss the solution as having no value without testing first. They are tossing out gold sometimes when they do so. Not every time perhaps depending on their procedures, but often enough. 

I do much of my gold digestions with HCl and Cl2 gas (chlorine gas), as such there is no nitric to be carried over in the process. If I precipitate this gold with SMB from a dirty solution and need .9995 gold I will decant and wash it in hot water. After decanting again I add HCl and put the beaker on a hot stir plate with a stir bar included. I set the temperature to about the same as a hot cup of coffee and set the stirrer to high. The stirring action chops significant air into solution (the air we breath is roughly 21% oxygen by volume). This gives enough oxidation potential to the solution to digest finely divided gold in a reasonable time frame. I then re-precipitate my gold. 

Now it is fair of you to say that since I do this intentionally it has no bearing on the subject at hand. Let me give you this to consider. Platinum is far more difficult to digest in HCl and the oxidizer of your choice than gold is. Cold temperatures also slow down chemical reactions. One winter I had cemented some Pt from a chloride solution with zinc. I decanted it and washed in HCl to remove any excess zinc, then decanted again and added some water and a little HCl to prevent freezing since I was setting this aside until I had more Pt to add to it (it was only about a quarter of an ounce). This Pt ended up setting for 2 months in weak hydrochloric acid with only exposure to the air with no agitation or stirring. In that 2 months enough of the finely divided Pt had gone into solution to significantly color it. I decanted this and cemented enough Pt out of the solution for it to be worth the trouble.

I am not out to sell what it is I do to others, it works well for me. Neither am I just some armchair refiner, I have more than a slight clue as to what I do and see when I refine. You will find that when I post direction on the forum I speak from my own experience with repeatable results, if not of my own experience I say so. I am not a fan of unfounded idle speculation. Nor am not out to rewrite Hoke or anything else that has been written by others. I am here to say however that the books are not always right or do not always tell the whole story. 

Would you wish I only tell people what is in the books, or is it more beneficial for me to tell them what is not in the books? Some of the most valuable things I have learned on this forum came from experienced members that were teaching something from their own experience that is not found in the books. I believe in giving back.

If you still doubt me, follow my procedure and then come back and tell me if I am wrong. 

My intent here is only to educate members that they should test their wash solutions before discarding them. They work hard for their gold, I would like to see them keep all of it. It would be a shame to discourage such a simple precaution as a stannous test.


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## Harold_V (Dec 19, 2010)

mic said:


> Oz said:
> 
> 
> > plain HCl can digest gold. As part of my gold refining routine I take my once refined gold powder (after washing) and place it on a hot stir plate in HCl to re-digest it for precipitating a second time.
> ...


No, no need to rewrite Hoke. I am of the opinion that HCl is NOT dissolving gold. I've had a similar experience, which I found not to be dissolution at all. 

I experienced gold chloride when washing gold on rare occasion. Finally isolated the problem as _*drag down*_, where I had precipitated a large volume of gold (this occurred when I re-refined) which had trapped some of the gold chloride---to be exposed when I started washing. 

Solution?
Piece of cake. I learned to stir the precipitated gold well, and to add a little more ice if the solution was hot (often very hot), which immediately precipitated the residual gold. Note that I had SO2 running through the entire operation. 

I can honestly say that in all my years of refining, I never, once, knowingly, had a problem with HCl dissolving gold.

Harold


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## Harold_V (Dec 19, 2010)

Renaldas said:


> I read advices to boil precipitated gold powder in hydrochloric, nitric, sulfuric acid, wash with ammonia and use more substances. What do you think about boiling precipitated gold powder boiling in HCl, where several drops of nitric are added (such a very weak AR)?


What do I think?
I think you need to lose that idea and pay attention to what has been proven to work reliably. Part of that is losing the notion that gold, after precipitation, should be washed with nitric in any way. It's not necessary, and can be the source of one hell of a lot of frustration. You can achieve gold above industry standard (9995) by simply washing properly, and using good, clean handling practice. 

There's no way in hell you should be washing gold with AR---regardless of how dilute it may be. What's the point? 

Harold


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## Renaldas (Dec 19, 2010)

mic said:


> samuel-a said:
> 
> 
> > it's hard to tell by the picture, but trust me, this is purple, and the powder washed well with platy of water.
> ...



Maybe there are not nitrates, but air oxygen? I also have positive test for gold after boiling in HCl. As you know, combination of oxygen and HCl act as a weak AR.


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## samuel-a (Dec 19, 2010)

Oz

I couldn't have said it better... use your own experience, and test acid washes as well, that's it, sometimes it's positive, sometime it isn't...
I didn't spoke about the "why gold may be present in HCL wash" , only the "if it is there, then..."

the main point again, test with stannous...

Good luck to all


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## Lou (Dec 19, 2010)

Gold will certainly dissolve in hydrochloric acid that is open to air. It will not be quick at high temperatures, but in a cold agitated solution, I can promise you that some gold will dissolve. This would only be significant if it were really cold out and the vessel were open with stirring. We have members here using compressed air and HCl to dissolve gold. 

Leave HCl open to air, when it starts to yellow then that is chlorine gas being produced that is dissolving in the acid. HCl is not an oxidizing acid, but the chloride counterion itself can easily be oxidized to elemental chlorine by oxygen in the air (which becomes water), just as Oz said.


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## dtectr (Dec 19, 2010)

samuel-a said:


> mic said:
> 
> 
> > Do we need to rewrite Hoke and the forum handbook?
> ...



IMHO, I think we're apples & orange-ing here ...
Sam is not dissolving & then precipitating gold - he is inquarting, if his terminology is correct. 
Inquartation seems to be ALMOST a mechanical process (i know its chemical, officially; but follow me here)- 
The silver & base metals ARE dissolved, but gold is not, & is therefore NOT precipitated, as it never goes into solution to begin with; it merely remains behind as an INSOLUBLE. If the remaining gold particles are small enough, they would TEST as 
gold in solution, when in reality, they are really just really tiny insoluble PARTICULATES, not PRECIPITATES.

I think we're ALL accurate (obscure "Absence of Malice" [Columbia Pictures, 1993] reference),

Again, if terminology is correct ...

if I'm missing something, let me know ...
just my dos centavos


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## Harold_V (Dec 20, 2010)

Lou said:


> Gold will certainly dissolve in hydrochloric acid that is open to air. It will not be quick at high temperatures, but in a cold agitated solution, I can promise you that some gold will dissolve. This would only be significant if it were really cold out and the vessel were open with stirring. We have members here using compressed air and HCl to dissolve gold.
> 
> Leave HCl open to air, when it starts to yellow then that is chlorine gas being produced that is dissolving in the acid. HCl is not an oxidizing acid, but the chloride counterion itself can easily be oxidized to elemental chlorine by oxygen in the air (which becomes water), just as Oz said.


Interesting comment. I trust that the fact that I never worked with cold chemicals was the chief reason I had no problems? I would expect that the heated solution drove out any free oxygen, thus I had no problems. 

Harold


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## Anonymous (Dec 20, 2010)

Lou said:


> This would only be significant if it were really cold out and the vessel were open with stirring.


This may be why I have never experienced this.I've never used a stir bar,most of my soultions are heated ona hotplate,and even if they are not........I live in florida,we do not know the meaning of "really cold".


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## Lou (Dec 20, 2010)

Chlorine is well soluble in cold water. Once upon a time I worked on water sterilization--you'd be surprised how much chlorine will go into cold water. 

Funny thing is that the rate of dissolution will be less with the cold, but the solubility of the chlorine is higher.

You know it is the truth because HCl will gradually go from clear to yellow with oxygen absorption (which results in a reaction). Metals like iron promote this.

Lou


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## patnor1011 (Dec 20, 2010)

Now I am starting to be worried. 
I left fingers in AP outside for about 5 weeks now. Last time when I checked a week ago they were stripped clean but I did not had time to remove them 
We had very cold weather last few weeks sometimes up to -15`C so now my foils may be dissolved. Ill check that tomorrow.


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## Barren Realms 007 (Dec 20, 2010)

You should be ok.


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## adam_mizer (Dec 20, 2010)

Newbie here, reading this thread thought I would add in some of my small experience.

I have or had 25-30LB's of good high grade boards mix a little low most hygrade or thicker foil plate.
Removed the components with a heat gun.
Soaked these boards in HCl crock pot method. Earlier on I tested some small boards in a coffee pot and HCl to see reaction of old solder.
Some of the boards must have flash plate because when I pulled the samples out I saw the discoloration from Gold to nickel, I guess nickel under the flash plate.
The sample was done in approx 45 degree. (Lowes Muriatic 31.45%) HCl removed some flash plate.

The other day I ran several pounds of boards in the crock pot with lid and set on low/warm outside maybe 35 degree's. It did better as the flash plate withstood better this time but it still was noticable ever so slightly.
Most of the boards have heavy plate so I could not tell if any gold went into solution from them. But the gold does go into solution because the flash plated missing gold. Not much but it does!

So from reading I'm concluding that it appears that the small amount of oxygen striking the surface of the HCl bath does get into the solution but in my case only very slightly not bothering me (yet).
Somehow I don't think thats what I'm looking for.
But Harold say's the HCl won't pull the gold out and it is contamination of some sort then the circuit board with the lead, so the lead/tin is the contamination, (other than copper/nickel/gold/traces). 
It was nice to see solder lead was cleaned off very good to the surface (now very flat). After stashing the HCL away for another use I saved the bottom debree also for another day.

These boards are then run in AP. Added air-pump to the AP bucket after waiting many days of slow production. Wow now I'm cleaning out foils almost everyday. Solution is working great.
When I find out the solution won't work anymore then I'll test for gold in solution. Meanwhile I'm getting out all I can get. A few pounds of boards and also 1/2-1lb fingers at the same time constantly.
Boards put on their side standing up so to speak and air bubble flow between them with fingers spilled between them also. 

Funny that some of my foils are in tiny tiny pieces but I'm not complaining just learning to deal with it since its a hobby.


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## qst42know (Dec 20, 2010)

Harold. 

Did you use tech grade HCL from a drum or hardware store muriatic from a thin plastic bottle?

I wonder if that would be part of the difference?


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## Harold_V (Dec 21, 2010)

qst42know said:


> Harold.
> 
> Did you use tech grade HCL from a drum or hardware store muriatic from a thin plastic bottle?
> 
> I wonder if that would be part of the difference?


For general processing and washing I used tech grade, purchased in 55 gallon drums. However, when washing my re-refined gold, I used reagent grade. I used to buy it in 5 gallon lots. I understand the chance of re-dissolving gold, but I have to say, it simply was not an issue for me, even washing with tap water, which was my routine. I attribute that, chiefly, to the fact that I did everything at high temps---never cold. I expect that traces of gasses were evaporated quickly, thus avoiding any problems. And yes----I did test with stannous regularly. I learned, early on, how valuable testing is. 

I am of the opinion that if washing gold is producing gold chloride, there's something more at play than gasses that are being absorbed from the atmosphere.. such as contaminated HCl. 

I might also note that I was never stupid enough to mix acids----I was faithful to incinerate if I had need to go from HCl to nitric-----and never, ever, washed with nitric. In spite of what you may hear, you can rinse precipitated gold time and again and still not remove all HCl, so washing with nitric will always present risk of dissolution. It is expelled upon extended heating-- when drying, or by melting. 

Harold


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## Palladium (Dec 21, 2010)

Lou said:


> Gold will certainly dissolve in hydrochloric acid that is open to air. It will not be quick at high temperatures, but in a cold agitated solution, I can promise you that some gold will dissolve. This would only be significant if it were really cold out and the vessel were open with stirring. We have members here using compressed air and HCl to dissolve gold.
> 
> Leave HCl open to air, when it starts to yellow then that is chlorine gas being produced that is dissolving in the acid. HCl is not an oxidizing acid, but the chloride counterion itself can easily be oxidized to elemental chlorine by oxygen in the air (which becomes water), just as Oz said.



I've mentioned several times that i have been processing pins in my 15 gallons plastic barrel setup using ap and compressed air. I have a 5 micron polypropylene filter bag fiberglass resin glued to the hose that i use for bubbles. I process outside under a building that is open and temp right now is around 40-50 deg F. I've talked about the gold that will go into solution because the amount of air that i am putting into the system. There is only about 5 gallons of solution in the barrel and when i hit it with the air it increases the volume of the liquid 2 fold. Once i have filtered the ap solution the gold that is there is so small from being agitated that it is hard to filter and deal with. I have noticed that once the ap solution is filtered for any undissolved gold that i am still recovering gold ( dissolved ) from the spent ap solution in the next step. So yes gold does dissolve in hcl but it is a function tied to the amount of oxygen present and will increase exponentially as such. I love the cold for my processing. It just seems to work better for me than heat with my setup. 8)


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## Anarchy618 (Mar 13, 2018)

I have been adding small amounts of powder together untill I had a decent amount. When I tried to clean it with hcl to remove impurites before melting (due to dark discoloration of powder mixed with impurities ) what would make the solution turn so violently blackish & appear oily?


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## g_axelsson (Mar 13, 2018)

You should really invest in some proper beakers, it is so much easier to pour from to avoid spilling our precious gold. And using a beer glass is sending the wrong signals to your brain, it only takes a split second of confusion to make a mistake.

Göran


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## Shark (Mar 13, 2018)

To add just a bit more to Goran's advice. Those narrow bottom glasses make a nice visual when precipitating your gold, but they sure are easy to tip over when filled to the brim (I know they are weighted on the bottom, but accidents do happen). I have used all kinds of glassware and still use some, but my selection is shrinking constantly because of the faults I have found from actual usage. At a minimum use a decent glass coffee pot, and then, only if you restrain the amount of heat applied to it. Buy a beaker or three and be glad you did. They will take heat better than the average coffee pot by a large amount, and they have premeasured marks that help a lot. They also come in sets that really keep the costs down. I wish I had bought them sooner than I did.


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## 4metals (Mar 13, 2018)

I think we need to back up a bit. Maybe quite a bit. The acid turned that color from putting gold powder that was precipitated from solution in Hydrochloric Acid? Maybe we need to talk about what you did to get the powders that you attempted to wash. 

There is something you’re not saying going on here.


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## g_axelsson (Mar 13, 2018)

Anarchy618, Does this have anything to do with this thread? If it does, try to keep everything in one thread to make it easier to follow what you have done.

Göran


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## g_axelsson (Mar 13, 2018)

Anarchy618, Does this have anything to do with this thread? If it does, try to keep everything in one thread to make it easier to follow what you have done.
http://goldrefiningforum.com/phpBB3/viewtopic.php?f=49&t=15183&p=283801#p283801

Göran


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## Palladium (Mar 13, 2018)

Iron!


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## Anarchy618 (Mar 15, 2018)

Yes sorry Goran, I will pay more attention to not doing that. My apologies. I will reread the way the site operates. I'm just not used to using social forums (I don't even have or use a Facebook account) and im not used to communicating in this manner, especially when it comes to asking for help. But hey we all got our own issues. And I happen to value you guys & ur awesome unencumbered free help & advice. So plz do let me know if I do anything else unconstructive, for good constructive criticism will ALWAYS remain a good & helpful thing.


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## FrugalRefiner (Mar 15, 2018)

Anarchy618 said:


> And I happen to value you guys & ur awesome unencumbered free help & advice. So plz do let me know if I do anything else unconstructive, for good constructive criticism will ALWAYS remain a good & helpful thing.


OK, do not use text lingo here. We have members from around the world, and many of them have to use translators to read the forum. Things like "plz", and "ur", do not translate well.

You'll find a link to the forum rules at the top of every page. I also recommend reading the Tips for Navigating and Posting on the Forum thread to help you get off to a good start.

Dave


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## Anarchy618 (Mar 15, 2018)

No text lingo, got it. Luckily I never usually do so this rule will be an easy one to follow


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