Quote Originally Posted by nutpie View Post
You are saying dental x-ray machines have precious metals in them? I have picked up 3 so far and have been breaking them down and just scrapping the parts. I have one in sitting in my back yard right now. And I will probably receive more in the future. I will have to investigate this one. Maybe I will take a picture and post it.
The silver is in the film, as it being developed silver leaches out of the film into the developer leaving an image behind.

In the electromotive series of metals iron reacts with metals below itself in the periodic table. Some of you may have heard the term Pig Iron, yes a pig will eat most anything placed before it.

Ferrous sulphate is somewhat selective and is sometimes used to precipitate gold from a leach. Used in excessive amounts is known to drag down other precious metals and its recommended a second refining be carried out using a different precipitant on the second refining.

Something like oxalic acid could be used the second time to improve purity.



Photo and x-ray labs that use developers will have a canister could be a pail with a lid on it that they pass the spent developer through, the canister is filled with steel wool the pig.

As the silver laden solution passes over the steel wool an ion exchange take place, iron molecules exchange for the more noble silver which is deposited as a black sludge.

My Saskatchewan buddy also had his fingers into the demolition of the old Melville hospital, from the lab that processed the film the old cast iron pipe was half full of black sludge. And this sludge carried from the second floor lab right down to the utility room in the basement.

I noticed this when Bill was giving me the tour of the old building, told him to scrap out the sludge then save it in pails to send out for refining. Never got further involved in this project as I was visiting to get some old planks from the old pig barn on his farm to deck a trailer I was building at the time.

Must have been a good haul for Bill as he later gave me a lot of stuff from the Dental Clinic, not sure what happened with the clinic but it was as if the dentist went on vacation leaving everything behind. The building came up on a tax sale and Bill grabbed it up for a song.

I got the heavy metal traps, centrifugal casting machine, small electric gold and silver melting furnace, air compressor hand held high speed dental drills and boxes upon boxes of caps and crowns that I sold with most of those going to buyers in Mexico.

Dental labs have to pay to have the heavy metal traps taken away as hazardous goods and they receive no money for the precious metals inside.