John, in case your question is more basic (plus, Ed's stuff shows up in really tiny type on my system), the tech is more than likely just making a commercial mix. For example, the developer is probably from Kodak or Ilford, etc. It's probably either a plastic-lined bag containing a powder or a plastic botttle of concentrate; either is mixed into a certain quantity of water (say 1-gal) at a certain temp (maybe room temp for the liquid mixes). Ditto for fixer.(posted 8528 days ago)BTW, developers ususally need to be alkaline (ie, pH higher than 7) to work. The stop bath halts development by dropping the pH.
PS, at the bottom of the question page is a list of archived questions in categories. I see there is a category for both chemistry and developer; you might want to spend some time browsing through there.