how to dispose of 22k testing solution?

I have a little 22k testing solution in a dish because I was told that
it was a suitable silver etchant. (It actually did not etch my
silver, but perhaps I did not leave it in long enough or my image was
too thin.) In any case, I need to dispose of it because it can't go
back into the little squeeze bottle and I'm moving. It is a pretty
small amount...does anyone know of the proper way to dispose of it?

thanks in advance,
-stacy