armymp1 said:
Yes I dropped 5 or 6 pieces into HCL after the reaction started boiling into poured an equal volume of water to slow it down. Any idea what the yellow to white residue on the edge of the bowl might be?
I put a gold plated PCB in nitric acid to flake the gold off but ended up with gold flakes in a gray sludge.
armymp1
I see a pattern here - one that is a "common" mistake among people wanting to get into the recovery of gold from electronic circuit boards (including me when I "first" started)
That mistake is --- "I can just throw it ALL in some acid & the acid will dissolve everything except the gold leaving me with nothing but the gold to filter out
Sounds easy enough - BUT - it doesn't work that way :!: - as you are finding out :!:
First of all (as you are finding out) different acids react different with different metals
For example - nitric acid will react to dissolve "some" metals - but wont react "at all" with other metals - & then again it will react with other metals, but not actually dissolve them & in stead change there chemical composition to a complexed salt of the metal (a state of oxidation that is in a solid form)
Example - if those CBs in the picture ( CB on top of the aluminum blocks) are the same ones you "first" put in nitric - & then put in HCl - you learned that the nitric dissolved copper - did nothing to the aluminum - & turned the tin to the sludge you ended up with
On the other hand - if you had put them (CBs) in the HCL first - it would have dissolved both the tin & the aluminum - but not the copper - AND - if you did not dissolve ALL of the aluminum in the HCl - the aluminum would cause the tin to cement (or precipitate) back out of HCl solution as a fine powder of tin metal --- that is due to where on the reactivity series different metals are & we use that (reactivity series) to recover metals from solutions by using one metal to displace another metal from a solution
The point being - you cant just throw stuff (CBs) into some acid & expect to have nothing but gold left --- doing so will result in nothing other then a BIG mess - &/or you asking - "where did my gold go"
You need to learn what acids are the right acid to target "particular" metals - & as well the right order in which to target the different metals
There is a book available here on the forum (for FREE) by C.M. Hokes that does an excellent job of explaining this along with small experiments you can do to become familiar with acids, metals & reactions
You will find the book for down load at the "bottom" of FrugalRefiners post here
:arrow: http://goldrefiningforum.com/phpBB3/viewtopic.php?f=54&t=19798#p201558
Now then - just for the sake of discussion - lets say there was an acid you could just throw the boards in that would dissolve everything & leave you with nothing but the gold - you would NOT want to do that anyway because ------------
1) you would use up a HUGE amount of acid - so much acid that the cost of the acid would be greater then the gold you would recover
2) AND - you would also produce a HUGE amount of waste --- TOXIC waste that you can not just dump down the drain - "toxic" waste that FIRST needs to be properly treated to dispose of it in a safe manner
That is why we FIRST "harvest" the gold bearing "components" from the CBs before doing any chemical work with them - that way we keep our chemical waste to a minimum - which in turn makes treating the waste for safe disposal much more manageable
Bottom line - there is a LOT for you to learn BEFORE you actually start playing with the chemicals - the good news is you have come to the right place to learn about this - GRF is the BEST source of info you will find
anywhere in the world :!:
So I suggest - for now - put the chemical aside - start doing some research "here" on the forum & when you have questions ask them & we will be glad to help answer them - & in the mean time keep collecting & saving CBs
You may find that the chemical part of this is not for you - but all is not lost because the CBs them selves a worth good money & there is "always" a market for them
And as a final note - the gold plating you see on the boards is not all of the gold CBs have to recover - there is more gold that you do not see - such as bonding wires inside the IC chips
Kurt