clean up corroded mercury oxide batteries

[crazyhog]

Hi all,

I have an old Keithley 502A from the 1970s that I'd like to repair.  It contains a bunch of large mercury oxide batteries.  Some of these batteries are the size of D cell batteries.  I am guessing these old batteries are the original batteries from the 1970s.

These batteries are badly corroded and the content of the battery has leaked.

I am concerned since mercury is poisonous.  What is a safe way to clean up all the old mercury oxide batteries? 

[bdunham7]

That's a serious problem.  Wear gloves, mask and goggles, dispose of them immediately after.  You can take the batteries themselves to your local city hazardous waste operation (although ours is closed right now for Covid19) but be sure and label them and put them in heavy, clear bags so that whoever works there realizes they are different.  You can buy a 'mercury cleanup kit' from industrial or lab safety supply warehouses, but they are expensive.  They will contain either sulfur or iron-zinc powder that will react with the mercury to form a much less toxic compound. 

Frankly, as much as I like fixing up old equipment, you might want to pass on that project.  If you do just put the whole thing in a clear bag and explain what you've got to the hazardous waste people.  That's a LOT of mercury in there, many thousands of times as much as in the old alkaline cells.

[David Hess]

Mercury cells convert mercury oxide to elemental mercury and the electrolyte is sodium or potassium hydroxide which is the same as with a NiCd, NiMH, or alkaline cell.  The elemental mercury (and mercury oxide) is very insoluble so should have remained inside the cell.  The leaking sodium or potassium hydroxide electrolyte will react with all kinds of metals and also produce carbonates from atmospheric carbon dioxide making a real mess which is probably what you see.

I would wear gloves but otherwise use the same procedures for cleaning up a leaking NiCd cell which includes lots of hot water and scrubbing.  If necessary, a weak acid can be used to dissolve any hydroxides and carbonates.

[amyk]

Organic mercury compounds are amazingly toxic, inorganic/metallic ones not so much.

[crazyhog]

Hi guys, thank you very much for your feedback!  This is very helpful!

[jogri]

If you have never worked with mercury compounds before you really shouldn't mess with them. Yes, elemental mercury isn't really toxic, but the oxide can and will be metabolized when it enters your body: It is insoluble in water and most organic solvents, yet it is highly effective at killing lab rats-> It probably isn't the HgO that is doing the damage, but some compound that got created by your body is. You are working with a substance that has a LD50 dose in the same range as most cyanides, that's not something to mess with. And it can get absorbed by your skin rather well, i wouldn't want to use an instrument that may or may not has toxic dust on it.

[Syntax Error]

STOP - Not wanting to sound melodramatic but can I ask, what is the chemistry inside those leaking batteries? Are you dealing with Zinc Mercuric Oxide batteries, or Cadmium Mercuric Oxide batteries? Both are hazardous (and banned) substances, but if mercury is bad, then cadmium is very bad. If not for you, then for the low wage slave at the recycling center.

I remember dealing with some ancient rusting ex-navy radio equipment that had to be wrapped and certfied a hazmat due to the cadmium-mercury power cells.