The Merck index says "Potassium Sulfite is soluble in 3.5 parts of water", Though doesn't say if thats the anhydrous or the hydrate.
If you take that as Weight for weight,Thats a 28.5% solution . (or 285g/Litre)
So I would say 250g / litre should go together OK (And keeps the sums easier if you're making a stock solution for using in other stuff)
It also says that its Cathartic and Diuretic, so wash your hands afterwards before eating, unless you want to be fixing prints in the bathroom, sitting on a porcelain seat
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