A speculation.(posted 8168 days ago)Anchell and Troop says PF version is based on FX-2 but with proprietary modification to improve consistency and gradation. Based on this statement, the most obvious thing that comes to my mind about what they have done to original FX-2 is to replace potassium carbonate crystalline with a mixture of carbonate/bicarbonate buffer of a certain fixed ratio. Having observed Troop's experimental formulae, he might have taken bisulfite path to the slight buffering effect, but the end effect is pretty much the same.