Subject: Why does zinc metal turn black when exposed to hydrochloric acid?

Thank you for your try at my question (http://www.madsci.org/posts/
947350993.Ch.q.html)!  Unfortunately, the explanation is without validity.  Zinc
chloride is a white solid, quite soluble in water.  Recently I attended a
workshop for chemistry teachers and no one had an answer although they all were 
aware that zinc metal will turn black in hydrochloric acid.  A few years ago I 
contacted Flinn Chemical and they couldn't explain it either!  Someone out there 
must know and I'd sure appreciate knowing myself.  I hope you can find
that someone and bring this query to a close.

Thanks again.

L. Schroeder

Re: Why does zinc metal turn black when exposed to hydrochloric acid?