1. Thanks for all of your input and i will research more into all your suggestion and find the best and safest way to do it.
2. How poison is the nitric acid gas formed with a very small amount of work, may be 5 ml at one time. I read on the internet, when use nitric acid to dissolve copper, the poison gas may cause endema, and possibly death? How do the school exhaust the poison NOx gas form, into the air? will the gas formed dissolve in anything, like water to form something that is not poison any more? besides, the poison gas form, I do not know if nitric acid will dissolve nickel alloy.
3. Member Borek, Member Chenberier, how danger if i put little may be 5ml 30% sulphuric acid and 5ml 3% hydrogen peroxide and a small piece 0.3mm thick X 5mm diameter sleeve X 7mm height nickel copper in a closed glass container work in a open air backyard? Is this process even more dangerous than the piece to be put into a nitric acid solution?
4. Member Anthrax, I am not in a hurry, I want to find an easy and safest way to this. The glass i want to save is very cheap and do not worth to risk my life to save them but i have many thousand peices so i cannot afford to throw them away. I can wait 2 weeks or 3 weeks to let it happen as long as the investment is not too much and it is a safe method. I am not sure if the nickel copper will dissolve like the copper alone. Can i use the baking soda as the Sodium bicarbonate? it is hard to connect the piece of rivet to a graphite electrode. May be i will found a electrode that is round and fit loosely into the sleeve rivet. what if there are some piece that do not contact well with the electrode, only result is copper do not dissolve?
5. Member Borex, i do find Sodium persulfate online, it is used for etching copper. it is not too expensive, i do not know how long it will take to dissolve the nickel copper alloy to a point that i can deform it easily mechanically to take it out safely. i will give it a try. thanks.