If there is only potassium and nothing like sodium etc in it I don't see why not. I did the same with some old iron pills.

Yes you can. And any old vitamins and minerals tablet that are to old for human consumption can be used for that purpose but with hard tablets I find it best not to ground them up because then they desolve all at once were if you leave them hole it becomes a time release.

thanks for your reply .

Bump! First I've heard of this idea - and I almost missed it.