Wow, 5 lbs of thiosulfate per gallon of fixer...I use 2 lbs and 4 ounces of sodium sulfite. I don't know how a person could get 5 lbs into solution. Even the Kodak F6 and F24 formulas call out 32 oz of Sodium Thiosulfate per gallon... the Kodak formulations do have additional ingredients apart from the plain hypo formula that I alluded to at the outset.