I wasn't sure where to put this interesting piece of info, so I'm putting it here in the Pool Water Chemistry thread since it is related to the chlorine/CYA relationship. This link describes a patent where a fluid is initially viscous in order to carry particulate matter and then becomes less viscous (more fluid) over time in order to deposit or settle its particulate matter. The patent uses a thickener, a hypochlorite, and cyanuric acid. Differing ratios of the CYA to chlorine determine how quickly the thickener breaks down (which changes the viscosity of the water). It's interesting that this is a patent that DEPENDS on the chlorine/CYA relationship for its proper functioning in having only disinfecting chlorine (that is, chlorine not bound to CYA and probably only hypochlorous acid) break down the thickener and having that concentration (and therefore reaction rates) be dependent on the chlorine/CYA ratio.

Richard