A week, or two ago the question was fielded where do I go to get a good density controller for my nitric acid based solder stripper. I am aware of what I consider to be the premium source for this piece of equipment, and indeed, some of the chemistry vendors are buying this unit, and relabeling it, and selling it as their own, at only a modest markup. So, I went to find the information on who/what/where, and simply could not find it. I initiated a total search and destroy mission, and simply could not come up with the information. I was terminally frustrated. Today, I was cleaning my desk for important visitors tomorrow, and Lo! there, in the middle of my desk, in a pile of junk was the information I thought had vaporized. At any rate, contact, Optrol Inc. about their model 131 controller. They are located in Raleigh North Carolina, (830-G Purser Drive) Raleigh NC 27603. Phone (and fax) is 919-779-3377. And when you need the chemistry, contact me. Rudy Sedlak RD Chemical Company