Richard you're absolutely right about makers of trichlor not being straightforward. I use the stuff when necessary and usually every few years I'll get a bucket, usually at Sams Club. There are two flavors, one is plain, the other is labelled as multi-purpose or something like that. The ingredient labels are virtually the same. Does one have copper or other junk in it? Would never know from the label. I would think they would HAVE to tell you but guess not. I always opt for the plain vanilla variety. Thought it worth mentioning again.
Al