I read somewhere if you measure specific gravity of the Pre-mixed ( koh+distilled water ) u can measure KOH percentage but for that you need hydrometer and in india there are two types of hydrometer used one for aquarium and one for battery but both cannot use to measure SG of KOH :(
Response From by: Hydrogen-Generators-USA.com
Deepak,
If I understand your question correctly -I don't know how to measure the % of KOH if it is pre-mixed. It would be easier just to flush and start with a new batch of catalyst.