Oh, I forgot to ask: About your used ferric chloride, what was used for? I mean what other things are dissolved in it besides Fe+3, and Cl-? If it was used for etching copper-clad circuit boards, then it is full of dissolved copper. BTW, since you are wondering about how to dispose of used etchants, I think there are processes for recycling/regenerating the etchant that are maybe even easy enough to accomplish at home... For example I think you could pull the copper out of your used etchant through electrowinning.http://en.wikipedia.org/wiki/Electrowinning Oxidizing the spent Fe+2 back to Fe+3 may be more challenging. But there are other etchants, like cupric chloride, CuCl2,http://members.optusnet.com.au/~eseychell/PCB/etching_CuCl/index.html that are easier to regenerate. Also, Youtube chemistry guru, Nurdrage, made some videos on the subject of homemade circuit board etchants.Make 10 Etchants for Copper Printed Circuit Boardshttp://www.youtube.com/watch?v=Q4tWEse2rDIMake Ferric Chloride (for etching printed circuit boards)http://www.youtube.com/watch?v=43Xsh9J7S-g Anyway, what I was originally going to say is, if your used echant does not contain anything more toxic than dissolved copper,then it's probably OK to dump it on the lawn. However, if for some strange reason, your etchant has more toxic metals, like lead, mercury, arsenic, plutonium, etc, then you DO NOT want to dump it on the lawn. For those kinds of dissolved metals you probably want to take it the place that takes accepts car batteries, and other kinds of batteries, for recycling. If necessary, label it as "battery acid", if that's what it takes to get them to take it from you.