Sciencemadness Discussion Board

Why is my mercury doing this?

itsallgoodjames - 15-3-2021 at 18:35

For no apparent reason, my mercury metal all seems to have formed tittle balls of metal about half a millimeter across that don't want to go back into one bead. Is this normal behavior for mercury? I'm dumbstruck as to what could have caused this.

link to video

Boffis - 16-3-2021 at 01:22

This is probably caused by a thin layer of oxide, try washing with a little very dilute nitric acid briefly. 1-3% is strong enough and less than 1 minute is usually long enough to fix the problem. If this doesn't fix the problem then you may have contaminated mercury which is harder to deal with.

itsallgoodjames - 16-3-2021 at 02:04

Ok, thanks. I don't have any good HNO3 currency. I guess I'll wait until my new acid arrives in the mail, then I'll clean it. As an alternative to that, would a HCl/KNO3 mixture work or does it have to be just straight nitric?

Bezaleel - 16-3-2021 at 04:45

It might become a strongly oxidising mix using HCl, although in low concentration it's probably not a problem. Maybe HOAc is a better idea?

unionised - 16-3-2021 at 04:52

It may just be oily, in which case a wash with acetone or something like that will work.
A rinse with alkali might strip the grease with less dissolution of the mercury.

itsallgoodjames - 16-3-2021 at 05:39

Quote: Originally posted by unionised  
It may just be oily, in which case a wash with acetone or something like that will work.
A rinse with alkali might strip the grease with less dissolution of the mercury.


I've run out of acetone just recently. Do you think that isopropanol or ethyl acetate could work instead? Also I think I figured out where the oil is from. I cut open 100 tilt switches to get the mercury, and the tools that I used almost certainly had some oil on them.

woelen - 16-3-2021 at 06:56

Use a solution of KNO3 in dilute H2SO4 for washing the mercury. The sulfate ions and potassium ions are just spectator ions. This solution works best as a substitute for dilute HNO3. I would not use HCl + KNO3. The chloride will increase solubility of the mercury (by complex formation) and may lead to excessive oxidation of the metal.

Boffis - 16-3-2021 at 06:57

Actually any dilute mineral acid should do the trick. Not too strong and no oxidizing agents like H2O2! You only want to remove the oxide film.

Like unionised said it could be oil in which case almost any organic solvent will do, pet ether, MEK, acetone, Perc etc.

unionised - 16-3-2021 at 07:52

Quote: Originally posted by itsallgoodjames  
Do you think that isopropanol or ethyl acetate could work instead?


I would try ethyl acetate first.

The advantage to using an organic solvent is that it will not dissolve so much mercury and thus be less of a mercury disposal problem (I'd probably say that, on a domestic scale, you don't need to worry about the solubility of Hg in EtOAC).
It's also less of a waste of mercury.

And, for similar reasons, if the stuff doesn't work, I'd try alkali before I tried acid and I'd use something like HCl before I added an oxidant.

Johnny Cappone - 16-3-2021 at 10:02

During the removal of mercury from the switches, did you allow it to come in contact with other metallic parts of the component? Did you store it during the entire process in glass jars? This behavior is familiar to me when I was dealing with some mercury amalgams.

itsallgoodjames - 16-3-2021 at 10:53

Quote: Originally posted by Johnny Cappone  
During the removal of mercury from the switches, did you allow it to come in contact with other metallic parts of the component? Did you store it during the entire process in glass jars? This behavior is familiar to me when I was dealing with some mercury amalgams.


I didn't let it touch the leads if that's what you're asking. The mercury did touch the pliers I used, but I can't imagine that causing any amalgams. I think what happened is some of the oil from the pliers came off onto the mercury.