# caustic soda



## superten67 (Nov 24, 2012)

could someone tell me please that not in my wildest dreams will caustic soda a disolve gold?
i must be the unluckiest person where buying chemicals is concerned but as you know here in the uk we're not allowed to have so much as a sharpened stick as a private individual.
but i dont understand how i can clean my drains if the chemicals are so weak i could wash my face in em.
i have put some touch pad boards in a saucepan with 500grams of caustic soda(as we call it)and after boiling it for ten minutes its just about comming off.
but the gold is very discoloured and looks to be gone.
but not like in laser steves video.
im at a loss does the stuff come in different strengths?if so ive never known it in all he years ive used it for drains and dissolving hair blockages etc.
any ideas guys?


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## nickvc (Nov 24, 2012)

To be fair it's easier to get chemicals here in the UK than in the USA or Canada, you just have to search for suppliers in your area, use a google search I'm sure you will find someone.
As to losing your gold in caustic no it won't happen but it will attack zinc and aluminium and perhaps if it's lost it's strength then it's plating back out of your solution and coating your gold.


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## superten67 (Nov 24, 2012)

cheers nick i think thats whats happened its stripped lots of it but there are large patches that are un stripped im getting well fed up of it.
i bought it from a bargain shop in burton so as you say chances are it might be past its sell by date.
i know some chemicals degrade i know explosives do so i suppose everything must have a life but just never crossed my mind.
where in brum you from mate?


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## butcher (Nov 24, 2012)

Caustic soda, Lye, sodium hydroxide, NaOH, is a very strong base the opposite of acid, it will not dissolve gold, some base metals can react with it to form oxides and hydroxides of these metals, or the metals may break down like solder.

Caustic soda can react with oils, and other organic material, like oils in your skin or hands making soap out of your skin, this is why when getting it on your hands they feel very slippery, and come so clean, dissolving your skin making soap, in the old days when it took many months at sea to travel, if someone died on ship they could dump the mans body over board into the sea, to prevent disease on the ship, but if they wished to keep the man and bury him on land, they would pack his body in a wooden barrel of caustic soda, the caustic soda would make soap out of his flesh, they could dump this soap overboard and take his bones to land for burial, caustic soda made from leaching wood ash, and animal fat (hog fat) was how soap was made it makes a very good soap when just slightly caustic, I have used wood ash caustic soda when making leather out of animal hides, the hide soaked in caustic soda make's the hair and fur very easy to remove from the raw hide, it also breaks down the fat and scarf skin making scraping the raw hide clean an easier chore.

The caustic soda can get under the solder mask (green coating) on circuit boards and loosen it.

The gold discolor you see is most likely just base metal oxides, or some other material, from the circuit board coating the gold not dissolving the gold, I suppose with very thin plating the base metal under the gold could oxidize and discolor the metal and make the gold look different, or even dislodge some gold as fine powder into the solution, but the gold would not dissolve into solution.

For a metal to dissolve into solution it must lose electrons, sodium hydroxide cannot take an electron from gold, the gold is too un-reactive.

Sodium hydroxide (caustic soda) if you get it in your eye, will easily dissolve, or cook the eye, and blind you, eye protection is a must.

Caustic soda NaOH the opposite of an acid a very strong base, which can burn your skin making it into soap by dissolving the oil out of it, if mixed with a strong acid like HCl in correct proportions until the solution becomes neutral pH7 will make sodium chloride NaCl (what we eat as table salt).

NaOH + HCl --> NaCl + H2O

Since the gold will not dissolve but some of it may loosen as fine powder, I would stir the boards in solution and rinse them off with a spray bottle back into the caustic solution, let your caustic solution settle well, decant the solution (use or save this solution to treat your acidic waste with), now carefully adding acid to the remaining powers and materials in the bottom of the bucket neutralizing the powders to salt pH 7, let settle decant salt water, then use boiling water to dissolve salt, and any water soluble oxides, or chlorides (like lead chloride soluble in hot water, not very soluble in cold water), this would leave some of the less reactive metals, any gold or silver that may have dislodged mixed with solder mask flakes or other trash, these can be incinerated, cooled, boiled in HCl, to help remove tin and other soluble chloride metals from these powders, boiling hot water washes will help to clean these up further removing lead chloride, and other base metals, letting the solution settle well before decanting but keeping solution hot (silver chloride is not soluble in hot water, but is fluffy and easily floats around, so keeping the water wash as hot as possible and letting silver settle before decanting the lead chloride), if washes were colored strongly I would repeat acid and water washes, this should leave you with any of the more valuable powders if they were dislodged from the original material. 

Some times there are ways to make your own acid or chemical you need, if you cannot get it, from chemicals you can get. 
Just a few examples:
HCl acid can be made from salt and sulfuric acid.
Nitric acid can be made from sulfuric acid and nitrate fertilizer or stump remover.
Ferrous sulfate (copperas) to precipitate or test for gold can be made from Iron and sulfuric acid.
Poor mans aqua regia made from HCl and nitrate fertilizer.
Ammonium chloride can be from ammonia and HCl.
Actually sulfuric acid can be made from rocks :lol: , but most countries use batteries and sell sulfuric acid.

The work around methods are very useful and can sometimes be preferred for some materials, like the copper II chloride leach for copper, or the HCl sodium hypochlorite to dissolve gold.


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## nickvc (Nov 25, 2012)

Many processes are slow to complete especially work around ones but take advantage of that by reading about your next steps and getting them fixed in your mind so your prepared to get to the end without problems. For many finding material containing values to work with is the biggest problem these days especially as a hobbyist or home refiner where there's no economy of scale, to make it pay at best or at least cover costs at worst, so if you have that covered your lucky.
Getting all the chemicals you need is fairly easy here in the UK especially if you explain to the suppliers exactly what your doing with them and many can be very helpful about other supplies such as lab glass, filter papers and the other pieces of equipment that we use that they might not sell, some sell all the items you need.
One good supplier of various chemicals and equipment is Scientific and Chemical 01902 402402 they are in the midlands and have a counter service where you can collect your materials or free delivery depending on a minimum order of around £100 if I remember correctly.
Melting dishes, crucibles and other refactory materials are eaily available here in the jewellery quarter in Birmingham during the week but most offer a postal service, Cousins and H.S.Walsh are two that leap to mind.
Hope this helps and keep at it and do your studying here on the forum, if it was easy everyone would be refiners.


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## superten67 (Nov 25, 2012)

tell me about it,ive done a few cock ups but managed to pull it back so im a bit more carefull now.
where are you from nick ?i used to live in erdington and walmley and how do you do your refining is ita hobby or do you do it for a job?


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