Problem with nitrate leeching

[kjavanb123]

All,

I processed PCI slots removed from a motherboard using a dilute nitric acid, but it seems the heat from reaction melted some of the plastic, and I don't see any gold foils. How do one avoid this mess? put the beaker before mixing the acid with slots in an ice bucket? I am filtering everything, then hcl/cl the remain.

Here are the pics,


side view


Thanks
Kevin

 

[maynman1751]

Some plastics don't like nitric, as you can see. Your gold is probably a fine black powder, there's not much gold on those pins. I would run all the solids with HCl/Cl, filter, eliminate the excess chlorine, test with stannous to see if there is any gold and if there is and drop your gold. Don't expect much from that quantity of material.

 

[kjavanb123]

I tried a new PCI slot with boiling dilute HCL, and after few minutes plastic started to melt like it did with nitric, it seems certain types of plastic bearing pins on motherboard are dissolving with acid no matter what the temperature is. Also some of the pin on slots are gold plated and yellow on the tip, while others are silvery color on tip.

Regards,
Kevin

 

[kjavanb123]

Also, tried one sample slot with dilute nitric acid and the plastic didn't get dissolved, so I assume the heat of reaction might be the cause of melting the plastic bearing. As you can see this slot contained a very small amount of low karat gold as it floats on top of surface as base metals dissolve in nitric.

The slot being processed in dilute nitric


The slot in the nitric acid and water with gold foils floating on top, the color of them are not the 24k color.


Regards,
Kevin

 

[kurt]

some plastic used in those type slots will be effected by acid & other plastics used in the same type slots wont be effected by acid so it does not mean that the plastic was not effected because the acid was dilute.

I tried doing a large batch of those type slots one time (about half a 5 gal bucket) & some plastic was effected by the acid while some was not - turned out to be a real mess which is why I just sell them for the $2.50/lb they go for now

Kurt

 

[Palladium]

I've found most black plastics hold up fairly well. Find some white ones and try them. Most times they turn to goo.

 

[kjavanb123]

Do all PCI slots or IDE connectors have gold? This one I have tested doesn't seem to have any gold foils or gold related items available after being in dilute nitric acid.

Palladium,
Yes most white plastic bearing components "melt" in acid.

Regards,
Kevin

 

[Geo]

Kevin, most do, if not all. the problem is gold is so thin and covers so little space that it takes a lot of material to see any gold. too, when you dissolve PCI slot pins in nitric acid, the pins are made of bronze instead of brass or plain copper. bronze is an alloy of copper and tin. most of the gunk in there is metastannic acid.you wouldnt be able to see the finely divided gold in all that with a microscope. well, at least it would be very hard.a better option for these types of pins is the stripping cell. it doesnt matter how much or how little, the cell will get it all without the mess.

 

[kjavanb123]

Geo,

Great idea, I just watched Steve's video on sulfuric cell, and I will try to test it with it. The only disadvantage to it is removal of pins from the plastic bearing slots, so I assume that can be done by melting the solders at the bottom of slots.

I will post pics as I proceed with sulfuric acid cell.

Regards,
Kevin

 

[kurt]

I've found most black plastics hold up fairly well. Find some white ones and try them. Most times they turn to goo.

I have had black plastic effected by acid as well. --- Did a bucket full a couple years back - all the same type pins all in black plastic - about 15% of the plastic went to heck in the acid - made a real mess out of the whole batch - thats when I decided I will only process "full" plated pins that are easy to remove from the plastic & sell the rest for $2.50/lb

Just saying type of pin &/or color of plastic is not an absolute indicator of what will or wont hold up in acid

Kurt

 

[kjavanb123]

All,

Per discussion about sulfuric acid cell, I tested the following.

I connected a PCI slot which i already tried with nitric and know it had gold foils to a copper rod, the rod was in the middle of the solders so that way electercity was going through all the pins.
another copper rod was used alone as cathode. I used a 12v 2amps AC-DC adaptor and connected the copper rod attached to PCI slot to positive, and other copper rod to negative. all inside a 100ml of concentrated sulfuric acid with a teaspoon of glycirite. Immidate reaction started and small amount of black cloud formed on the slot.

Is this adapter going to the job of a rectifier?

Thanks
Kevin

 

[Geo]

ive seen members use a flat piece of copper cut to fit the slot like a finger board. plug the copper piece in the slot to make contact with all the pins and your good to go.

on a side note, theres no need for the glycerin. as a matter of fact, it could be very dangerous if you were to add the littlest bit of nitrate to the mix. nitric acid + glycerin heated in a solution of concentrated sulfuric acid produces nitro-glycerin. very unstable stuff. Steve's video has it in there because at the time, he was following directions from someone he met on the internet (i believe). glycerin is used to help reduce metals from oxides, but its not necessary for the stripping cell.

 

[kjavanb123]

All,

I have finished processing most of the components from a Chinese made PCB, and PCI slots, memory slots didn't have any visible gold foils, however the USB ports, Ethernet port, and what seemed to be A/V ports the pins inside of them after dissolution in dilute nitric acid showed some gold foils.

CPU sockets, after dissolution in dilute nitric acid had some microscopic gold particles, but most of it is a grayish metallic which I am letting it dry out, to weigh then test it with AR and stannous to find it out what is it. I am guessing it might Pd.

Pictures are up soon.

Regards,
Kevin