Notes on Survival practical reactions to climate change

Lye, caustic soda or sodium hydroxide is hard to make. You have to use electrolysis on a sodium chloride (salt) solution. Sodium hydroxide builds up on the cathode, but then you have to find a way of stopping it reacting with the chlorine. From what I can make out you have to get a special membrane to separate the cathode and anode reactions. I can't see a low-tech way of doing this. Once produced, the lye is stored as a water solution.