Flux for Making a gold bar

[tvanasetta]

Hi all,

I got a powder from a supplier which they give no information on what chemical it is.

It is white powder, use as final flux when melting to make gold shinny. What I believe is it is some kind of arsenic. The supplier claim it is illegal to obtain (I'm in Thailand)

Anyone know about this kind of chemical?

 

[Harold_V]

A white powder covers so many chemicals that it would border on the impossible to make a safe prediction on what it may be, but there's a few things you need to know that may help you understand what it may be.

It most certainly shouldn't be arsenic. I don't see any reason for anyone to use that for the purpose. What I expect is that your supplier doesn't want you to buy the powder from other sources, where it would likely be far less expensive.

What is commonly used is boric acid, or borax. Borax absorbs oxides, and boric acid, if I am not mistaken (I may be) reduces oxides, so they are returned to the parent metal. In either case, neither of those chemicals are illegal, at least not here in the US. Each of them can be procured from any of the larger stores that deal with washing powders (borax) and have a pharmaceutical section, where you'd find boric acid. If you have no luck finding it, ask the druggist.

I'd like to add a comment. If you have done your refining properly, you should be able to melt your gold without losing the shine. All that should be required is that you coat your melting dish with a light covering of borax, so the molten gold glides across the surface easily, without sticking. If your gold requires flux as a brightener, it is not pure. Pure gold melts without discoloration, and fluxing only disguises the problem, it does not improve the gold quality, although a method for doing so is known. I tried it with less than good results.

Harold

 

[tvanasetta]

A white powder covers so many chemicals that it would border on the impossible to make a safe prediction on what it may be, but there's a few things you need to know that may help you understand what it may be.

It most certainly shouldn't be arsenic. I don't see any reason for anyone to use that for the purpose. What I expect is that your supplier doesn't want you to buy the powder from other sources, where it would likely be far less expensive.

What is commonly used is boric acid, or borax. Borax absorbs oxides, and boric acid, if I am not mistaken (I may be) reduces oxides, so they are returned to the parent metal. In either case, neither of those chemicals are illegal, at least not here in the US. Each of them can be procured from any of the larger stores that deal with washing powders (borax) and have a pharmaceutical section, where you'd find boric acid. If you have no luck finding it, ask the druggist.

I'd like to add a comment. If you have done your refining properly, you should be able to melt your gold without losing the shine. All that should be required is that you coat your melting dish with a light covering of borax, so the molten gold glides across the surface easily, without sticking. If your gold requires flux as a brightener, it is not pure. Pure gold melts without discoloration, and fluxing only disguises the problem, it does not improve the gold quality, although a method for doing so is known. I tried it with less than good results.

Harold

It is not borax I can get hold on borax easily and cheap too. But this powder is different, it throw a little in before pouring unlike borax this powder will burn and produce white stinky smog. Nothing stick on melting disk unlike borax. I try this with my 99.9 surface X-ray test refined gold. The different is the color, one using this powder is shiner and brighter.

Another clue I need to find is that this powder might import from Australia.

I got my hand on both industrial grade and lab grade. The industrial grade is cheaper and the powder is similar to salt. The lab grade is similar but the powder grain is more fine.


Main Difference between borax and this powder

1. When melting to a nugget and using borax when it cool down it seem to create gluey stuff, once it cool completely it seem to be a silicate dot on the nugget which can knock off with hammer or other tool.

But the powder I said, nothing is left behind only smog on melting pan.

I believe that major gold refining company use this powder when making a fine 99.99 1kg bar.

 

[teabone]

Sounds like salt peter , a strong oxidizer , but as Harold said there are many things with the same characteristics.

 

[tvanasetta]

as I browse through the web two think that point out are;

1. Arsenic trixoide
2. Sodium Cyanide

The people whom using this chemical without protection most of them get heart problem.

I can get the chemical but at hefty price, the seller call in special "Chinese name", so everyone know as that, but no actual chemical name or it property. Anyone know how to check out?

Also my fellow friend use it in jewelry making. He mix this mixture with water and boil the gold jewelry in it to make better color. - -"

 

[patnor1011]

I dont understand how one want to use chemicals which he is not sure about their composition and origin. Specially if they are "illegal" and hard to get. In my opinion its safer to get a ride on coastal drive with brake fluid drained out.

 

[Harold_V]

My limitations, due to not having an education, are now showing nicely. I don't have a clue what the powder might be. I do expect that it is a strong oxidizer, which is commonly used in the melting of gold to help eliminate traces of base metal. GSP has talked often of bringing gold fine in the melting process. It's a process I've tried, but with less than acceptable results. I attribute that to my approach, not that the method doesn't work. GSP has far more experience in the refining arena than do I.

Harold

 

[4metals]

I'm with teabone, it's salt peter, often called niter, and chemically called potassium nitrate. It works best in small quantities dropped on the molten gold in the crucible when the surface has a slight haze to it. A trick is to also add a pinch of borax before the niter so the oxides will collect on the sticky borax bead which always stays on the crucible wall when you pour. When you add salt peter a white smoke comes off and the niter sizzles on the gold surface.

Harold, your perceived lack of education didn't stop you from assuming correctly. I believe niter is what GSP is talking about as well.

 

[lazersteve]

I have recently tried sodium nitrate when melting my gold after it was discussed here.

When a pellet of niter was added to the molten gold button it danced and fizzed on the surface of the gold with several wisps of 'smoke', then rolled off of the button to the side of the dish.

The cooled dish displayed an unusual (compared to what I usually see when I don't use niter) yellow brown tint to the borax flux. I also noticed that after cooling it left a hard white 'salt' ring crusted on top of the transparent borax layer.

If you already have 99.9% gold why do you need to add a 'brightener' to it? As Harold pointed out, pure gold always cools with a bright finish for me. You can remove borax from a button with a dilute sulfuric acid boil and not harm the finish of the button.

Maybe your gold is not bright because the dish or your torch (assuming you melt with one) is contaminating the molten gold?

Steve

 

[goldsilverpro]

If you have 99.9% gold, the addition of a bead or two of niter can easily bring it to 99.95%.

 

[4metals]

I believe some of the old textbooks referred to adding niter to clean up a melt as toughening. Don't know why but maybe some of you may come across the term.

 

[qst42know]

I believe some of the old textbooks referred to adding niter to clean up a melt as toughening. Don't know why but maybe some of you may come across the term.

I had read once a reference to 1 part in 5,000,000 of lead can make gold brittle enough for the bench-man to detect. From an old text but I haven't relocated it yet.

 

[4metals]

I don't know about 1 in 5,000,000 but a slight lead contamination can cause a dip sample to crumble when you roll it. Guys who make alloy are scared to death of lead getting in their alloy.

It would be interesting to know the source of that reference.

 

[qst42know]

I don't know if this is the exact place I read it but here it is:

http://books.google.com/books?id=zi5VAAAAMAAJ&pg=PA907&dq=gold+brittle+lead

The fraction changes depending on where you find it. This one sites 1/1920.

http://books.google.com/books?id=AXsGAQAAIAAJ&pg=PA199&dq=gold+brittle+lead


The oldest texts are possible sources of misinformation as well. They don't often site the source of the science behind each statement.

 

[4metals]

Thanks, I doubt the older texts would reference a number of less than 1/4 PPM, not exactly detectable back in the day!

 

[qst42know]

I just re-read what I wrote it should have been 500,000 not 5,000,000. One too many zeros. One in five hundred thousand is 2ppm correct?

 

[qst42know]

I found this text referring to toughening gold. In which they use sal-ammoniac (ammonium chloride) and bi-chloride of mercury.

I think I would avoid the part about vaporizing mercury salts though. :roll:

Perhaps the illegal chemical additive your source is trying to sell you is a compound of mercury?

Full text is from here http://www.goldledge.com/history/docs_html/mineralogists_report.html



"In making a bar of cleaned skimmed metal it is necessary to throw a little powdered charcoal into the crucible before pouring into a mold, which insures a free flow of the metal from the crucible; it furthermore prevents spattering in pouring.
Gold bars received from the chlorination works are more or less brittle, therefore rendering this otherwise fine gold unfit for coinage, and this brittleness is generally ascribed to the presence of very small quantities of such metals as lead, antimony, arsenic, and bismuth, which metals have to be removed from the fine gold in order to render it "tough.”

These kind of bars are remelted in black lead crucibles, in which no fluxing had been done. When in a state of fusion repeated additions of sal-ammoniac is sprinkled on the metal, which exerts its influence on the lead principally, after which repeated additions are made of small quantities of powdered corrosive sublimate (bichloride of mercury). Care must be taken that upon the application of the latter the furnace door be at once closed, as dense and highly injurious fumes are immediately evolved. The corrosive sublimate is found to effect the complete toughening of the gold, by which the base metals are converted into volatile chlorides, and although the corrosive sublimate is only thrown on the surface of the molten gold (be there even two hundred to three hundred pounds of gold in a crucible), yet the whole mass is toughened by its action. When the gold is supposed to be toughened, a small portion of it is poured into a long, flat, iron mold. When set and cold it is folded back upon itself by hammering, and if not the slightest fracture is sustained the gold is considered tough; a little powdered charcoal is then sprinkled into the crucible, the mass well stirred, and poured into an iron mold. Silver bars are often very brittle, this condition being caused by the presence of antimony, arsenic, etc., rendering the silver unfit for coinage. In this case the bars are remelted with gold for subsequent parting."

 

[4metals]

I was taught that ammonium chloride was put on top of a gold bar which was poured with NO flux other than a possible niter use discussed earlier. A thin blanket of ammonium chloride covering the entire bar will easily fall off the bar and it is yet another tool to clean up a melt. The gold shines brilliantly from this treatment.

Right about now Harold may pop in to tell us that if you've refined it right to start with all of this is unnecessary. AND HE IS RIGHT!!!!! These are just a few tricks refiners have used over the years to further clean up gold in the melting process. If you refine it right, the gold will be bright!

 

[Harold_V]

I was taught that ammonium chloride was put on top of a gold bar which was poured with NO flux other than a possible niter use discussed earlier. A thin blanket of ammonium chloride covering the entire bar will easily fall off the bar and it is yet another tool to clean up a melt. The gold shines brilliantly from this treatment.

Right about now Harold may pop in to tell us that if you've refined it right to start with all of this is unnecessary. AND HE IS RIGHT!!!!! These are just a few tricks refiners have used over the years to further clean up gold in the melting process. If you refine it right, the gold will be bright!

Thanks for saving me the trouble! :lol:

The ammonium chloride process appears to be a variable of the Miller chlorine process. I would think that it would not be in anyone's best interest without an adequate fume handling system.

Harold

 

[tvanasetta]

Thank you 4metals

I had use ammonium chloride, it work as that unknown powder I used to use. Also ammonium chloride is cheap. All I do is sprinkle on the metal I use then pour the gold in it. It come out nice and clean without any discoloration. The slight discoloration could cause by small trace of other base metal. as image below

one on the right is using ammonium chloride on the cast.

It seem to be clearer than another one. It is from same batch of refining, I melt it to larger bar then separate in to two.