# foils disappeared in nitric



## DAVEEDO (Dec 14, 2011)

ok i got this purple-like powder. i had some foils in nitric that disappeared and this is what came out of it. is this my gold????


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## jimdoc (Dec 14, 2011)

Foils from what? In just nitric?
Do you have stannous chloride?

Jim


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## Geo (Dec 14, 2011)

purple is a good sign. if you had foil and now its gone, i would assume the purple sludge is the gold. did the foils come out of AP? if they did, did you incinerate the foils before you put them in nitric? AP is an hcl solution and you cant rinse acids off of your material. if the foils came from AP solution you created a weak AR solution.


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## DAVEEDO (Dec 14, 2011)

i had the foils from circuit boards and pins but i added nitric and distilled water to desolve the pins. after the reaction the foils were gone and the purple powder is what i was left with. the nitric solution turned blue. i assume its because of the silver. i had stannous but the rubber at the end of the dropper dry rotted out and crumbled


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## Geo (Dec 14, 2011)

ok. im sorry if i have to ask another question (i may be slow today) you was using nitric acid to strip gold plating off of some boards and pins and after the reaction the solution was blue and you had this sludge in the bottom of the container?


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## DAVEEDO (Dec 14, 2011)

oh no im sorry i wasnt clear. i stripped the foils with ap but there was still the metal pins so i rinsed the foils and pins and put them in a beaker. then i added a little nitric and distilled to desolve the rest if the left over pins and everything disappeared and left the purple powder


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## Geo (Dec 14, 2011)

ahhh, theres the problem. AP, like i said above is hcl acid, and you cant rinse it off no matter how many times you rinse. you can even boil in water and the hcl will remain on the material. finish dissolving whats in the filter with either AR or hcl/cl. just rinse the filter contents into a flask and finish the dissolution. the blue soltion will most likely contain some gold too. if you cant test just assume that it does and try to drop what will come out with a little SMB.


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## DAVEEDO (Dec 14, 2011)

so just add smb to the blue solution and the gold will drop out? thank you so much for your help. i was starting to assume thats what happened but we all know what happens when we assume right. again thank you so much


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## Geo (Dec 14, 2011)

a word of caution. there may not be that much left in solution. it looks like alot of material in the filter paper, remember, the purple is gold too.


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## jimdoc (Dec 14, 2011)

I had a bucket of gold turn purple on me by mixing another container into it. It surprised me, and I still don't know what happened for sure. I think there was solder in the second batch that made it like a giant stannous reaction. All I know is that I melted the purple powder into one of the nicest buttons I have made.

Jim


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## DAVEEDO (Dec 14, 2011)

thanks guys also i have a bit of "dirty foils " i call them cause, well theyre dirty. im going to post a picture in a minute maybe you can tell me what to do with them?


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## DAVEEDO (Dec 14, 2011)

i think theres filter paper that fell apart when i scraped the foils off of it


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## jimdoc (Dec 14, 2011)

I think you should incinerate it and process it separately. Or save it as is, until you get more stuff that needs incineration and cleaning up.

Jim


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## DAVEEDO (Dec 14, 2011)

im not too familiar with incineration. is that when i burn the filter paper with borax on top so the gold rises on top of the borax? do i need to do anything else to it? and how much borax do i use because i have many many dirty filters


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## Geo (Dec 14, 2011)

incinerate means to burn to ashes. in our case we would like to burn the ashes too but just make sure there's no black color left to the ashes. when you do it correctly all the ashes will be white. do not add borax to material you want to incinerate. find an old stainless steel pan, yard sale or thrift store type pan, something you will never cook in again. put all the material you want to incinerate (dry filter papers, bits of plastic with metal in it, etc.) and add a little, very little charcoal lighter fluid. place on a suitable spot that heat wont be an issue and light on fire. as the fire dies down shift the material around to insure all the material gets exposed to the air. after all the embers die and the ashes cool, collect and store or add to a beaker and process with hcl/cl.


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## butcher (Dec 15, 2011)

I feel Geo's method of incineration may work here, (if your just burning some dry paper) but I would not call it incineration, but maybe I would call it burning with lighter fluid.

Geo gives good advice but I wish he would not call this method incineration, as incineration is a different process.

Be careful with lighter fluid or cans of gas that fire can burn back to the can in your hand, or you may burn up more than what you wanted to.


I can pour lighter fluid in the palm of my hand and light it, (with my thick skin of my hands, I would hardly feel the heat as the lighter fume's evaporated off of my hand and burned in the air above my palm, with the fluid burned away so fast my hand would not even get burned.

Many things that need incineration need prolonged heat, getting everything (carbon based), that will burn consumed and converted to CO2 gas.

Powders (salts of metals), (any metal dissolved in an acid, becomes a salt of that metal and acid). 
We will also need prolonged high temperatures to convert the salt back into the metal oxide, of that metal, this heat drives off these as fumes of the acid we used to make the salt.

Example: say you dissolved tin in HCl with some gold, and then added nitric (dissolving gold and tin together) and formed some aqua regia, but the tin and gold and chlorides made a purple of cassius powder (tin chloride reduced gold),(same as stannous test reaction does), and I wanted my gold back from this mess, I would incinerate these powders, heating these metal chloride salts, to separate chloride (as gas) from the gold and tin salts or powders (this would take prolonged heating) (not just rising vapors of volatile lighter fluid burning fast off the surface), these salts once heated high enough long enough will change from being a salt of metal, back into the elemental metal, I still want to heat them longer till red hot until they no longer put off smoke or gases, this red glowing heated metal is crushed and exposed to air, this will oxidize the metal (making it easier to go into solution later), (in our case here tin will oxidize, so the HCl wash later will NOT make a gel (making it hard to separate gold from tin) and HCl will dissolve the tin-oxide easier).

(For some salts like sulfates made from metals dissolved with sulfuric you may have to heat 30 minutes to more than an hour to drive off all of the SO2 as gas and convert metal these salts into metal oxides).

Tin in HCl does not dissolve very well at all, and it makes a gel that gives trouble filtering, and it will also trap your gold in this gel, the incineration process converts the tin to tin oxide, so that HCl will dissolve this oxide of tin much better so you can wash tin from your gold (without washing away gold with it).

Many times we use incineration when changing acids (removing acidd salt previosly used.

When you dissolve a metal (or even wash a metal) in an acid you have the salt of previous acid, like when you make a chloride salt, (incineration drives off (chloride as gas) from the salt of the metal, changing it back into metal, or metal oxide.

Without incineration you have these chloride salts and when you add nitric on the metal (chloride) you will make some aqua regia, (from mixing metal chloride salt and nitric which would dissolve some or all of your gold), and then you have gold dissolved in the metal, (you were trying to wash away without dissolving the gold).

Incineration should be done with high heat.
For sulfates temperatures of greater than 700 degrees are needed, and these temperature's must be held for a long enough time to remove the SO2 gases, it could take an hour for these temperature to drive off all gases. Then heating these powders red hot in air to oxidize metals, these temperatures will usually take heat from a gas burner, torch,fire from coals, or electric burner with a torch, or other very high heat source.

Non-magnetic stainless steel, or white corning ware type casserole dish is what i would choose to incinerate in. depending materials what I was doing also would depend which one of these I chose.

Another thing to consider gold chloride salts (or even gold mixed with table salt) heating these you can evaporate off vaporizing the gold in yellow fumes (similar with silver chloride salts vaporizing in the white fumes).
To prevent this I will neutralize my Gold (or silver) chloride salts with sodium hydroxide, water and stirring well, this will take the gold chloride salt, and make sodium chloride (NaCl table salt) this Table salt water is easily washed out with several hot water washes, this prevents losses of values in fumes when I incenerate.

Another point some salts will need low heating to begin with (to dry), otherwise splashing and bursting gas bubbles will throw values all over the place, and then once these powders are dry, the heat can be raised (usually best to start crushing back to powder before completely dry, and continue to crush till well dried), now many times after you raise heat to high, on the dry metal salts, they will become wet again and form a thick syrup of fused metal salts, they will start fuming off acidic gases, keeping the heat high (but not bubbling and splashing), these acidic gases will escape and these metal powders will then dry again, we crush to powders again now we can bring these powders to red hot to oxidize these metal powders stirring the red hot powders well to get good exposure to air.

Inceneration sounds simple, it is, but this tool is one of the best tools in your tool box if used properly, it is very important if you want fine gold, keeps you from gold lose when changing acids, and is especially important when dealing with electronic waste with the tin involved.


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## Harold_V (Dec 15, 2011)

Geo said:


> incinerate means to burn to ashes. in our case we would like to burn the ashes too but just make sure there's no black color left to the ashes. when you do it correctly all the ashes will be white. do not add borax to material you want to incinerate. find an old stainless steel pan, yard sale or thrift store type pan, something you will never cook in again. put all the material you want to incinerate (dry filter papers, bits of plastic with metal in it, etc.) and add a little, very little charcoal lighter fluid. place on a suitable spot that heat wont be an issue and light on fire. as the fire dies down shift the material around to insure all the material gets exposed to the air. after all the embers die and the ashes cool, collect and store or add to a beaker and process with hcl/cl.


You're missing a golden opportunity here. 
Once the material has been properly incinerated, screen it, and check with a magnet to ensure there's nothing magnetic included. The resulting material should then be given a boil in HCl. It should then be rinsed well before dissolving the values. Tap water is perfectly acceptable for the rinse cycle.

This step is critical to successful filtering of the values. It's especially important if the material in question is the purple sludge that has been discussed, considering it tends to contain traces of tin, which really complicates filtration. 

Harold


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## oldgeek (Dec 15, 2011)

butcher said:


> I feel Geo's method of incineration may work here, (if your just burning some dry paper) but I would not call it incineration, but maybe I would call it burning with lighter fluid.
> 
> Geo gives good advice but I wish he would not call this method incineration, as incineration is a different process.
> 
> ...



Butcher, 

THANKS, for the great post, about incineration. You tend to explain things in a way I can understand. (i am kinda slow)  

I have been reading this forum almost daily for years now, and things are finally starting to click. 
Sometimes on this forum we are asked to do things, without clear directions how to do it. While a proper search of the forum will often yield directions for a particular process, sometimes it just brings up even more questions about what you are attempting to do. :lol: 

Anyways i sincerely appreciate your assistance, and the assistance of many others here.

Remember, it never hurts to "dumb it down" when possible (for my benefit anyway!)


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## butcher (Dec 15, 2011)

oldgeek, I just tried to explain what I have learned from others here and have seen.
I know that many times I do not explain things very well, now if I can draw a picture, some guys may understand what I am trying to say.


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## DAVEEDO (Dec 15, 2011)

i want to thank you gentlemen for the clearest answers to my questions ive ever recieved. thank you so much for all the help. i really dont know where i would be without all the fantastic help i get from all of you. i cant stress enough how gratefull i am that i found this forum.


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## Geo (Dec 15, 2011)

i agree that incineration is a prolonged heating and simple burning isn't the same and i really should have explained the difference but in this situation i gave the simplest directions i could think of to get what he needed to do done.

thanks Harold, it slipped my mind to mention the rinses even though i do them myself. sometimes i assume people are at the same level of knowledge as i am about certain things and the simplest things sometimes escape me. to be honest it didn't cross my mind to wash in hcl to remove the tin.


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## butcher (Dec 16, 2011)

Geo, I understood you, and the advice you gave, and considering his case, it was good advice.

I was afraid other new members may think that they can incinerate all powders or salts with just some lighter fluid, and a quick burn time, and wanted to clarify the difference.

Edit to add : Actually if it was not for safety concerns, the lighter fluid method may be good to remove light oils from some materials, (I use similar method with alcohol sometimes, but I will not recommend this on open forum, afraid some young fire bug may let this get out of hand). A torch is safer and that is what I recommend in this case, (heat from bottom so you do not blow away values).


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## glondor (Dec 17, 2011)

Butcher, that is a fantastic post about incineration. You did a great job of following through with your explanations. It is always better to know why things work the way they do rather than just doing something and not really understanding why you are doing it. You have done a great job with the "here's why" part. 

I love it when people qualify their statements and follow through with their explanations. Takes the guess work out. 

The one question I do have is when would you choose corning ware vs stainless. 

When I was half way through your tutorial I said to myself "I have got to find the books he is reading" I will be doing more incineration soon and I will have this post at my station for sure.


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## butcher (Dec 17, 2011)

I will use corning ware for salts that may eat (corrode the stainless) steel.

Incinerating in this dish allows me do almost the whole process in the corning ware dish without remove powders (or metals), so that almost the whole process, is done in the dish without moving powders from jar to jar, or removing corning ware dish from the hotplate.

The white corning ware dish, or the kind of vision-ware skillet pink, amber or white, these are very resistant to heat (but do not change temperature to fast), they are very strong to abuse, I have incinerated metals to red hot (even some metal melted with torch before), and not broke one yet.

example incineration done in corning dish to remove oil and carbon plastic, or convert salts to metals and oxidize metals, and so on, cool, add water, boil to wash the incinerated powders, let settle, siphon rinses,(repeat as needed) and continue with process, without removing materials from the corning ware dish (or dish from hot plate), I can go on and do a heated nitric acid leach, settle decant (siphon) nitric leach, boiling hot rinses, after settling, decant (siphon) repeat and then dry, re-incinerate, then an HCl wash (to remove tin oxide),settle, decant, boiling hot water washes (to remove lead),settle decant,(repeat if needed), then heated aqua regia (to dissolve gold), dilute solution and settle (silver chloride and other salts), then decant (siphon) solution into filter to get filtered solution into my clean jar ready for precipitating gold in.
This is not an actual process just an example.


Say I have a bunch of chips I want to incinerate, then since I always have pile’s of wood to burn or stumps, these provide my coal fire, here is where my stainless steel skillet is used pan filled with chips set on red hot bed of coals, incinerated till almost char, removed from fire and crushed while hot in skillet, returned to fire, powders stirred and exposed to air with heat, sometimes the pan will be removed from coal fire and a propane torch heats from above (we want to see the metal glow red but not melt). Now this is cooled sometimes panned, or screened and then processed in casserole dish as mentioned above.

I do have some fancy lab glass (put up clean and safe), but have not used it in my recovery or refining (yet) (call me funny but I do not want to break or scratch or get it dirty my pretty lab ware). Most of my lab is kitchen ware. It serves me well. Jars and such get used scratched or too stained they just get demoted to recovery, and a new pickle or canning jar is cleaned and ready to go onto the front line. Coffee pots (Pyrex or Mr. Coffee) I pay a quarter for, and get a heck of a lot of use out of one. Crock pots, blenders, coffee mug warmers. One of these days I may get some acids in one of those fancy lab glasses (maybe)?

Hoke's book is the one I suggest reading, even after you study it several times you will find things written between the lines, that give you ways to improve your processes.


Edit: I cannot remember for sure, but seems to me Hoke, recommended the cassarol dish to me in her book, along with my crock pot (not to be confused with the slow cooker I use), and some other tools I use.


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