This is a good thread. One pound of Caustic/ Sodium Hydroxide Beads or flakes (99% strength) in one gallon of water will make the solution about 11% Sodium Hydroxide. Three pounds of Caustic in one gallon of water equals about 32% Sodium Hydroxide Solution and Five pounds of Sodium Hydroxide equals about 54% Sodium Hydroxide. Most NaOH sold in drums contains 50 % Sodium Hydroxide so yes 5 pounds can be dissolved in one gallon of water. In my opinion and experience if you are using more than one pound in one gallon, it is not only overkill but dangerous. If by some chance you get this solution in your eyes or on your skin the burns are horrible not to mention blindness can occur. Some of us have experienced this type of burn and I promise you it isn't a nice one. Just be safe and wear proper PPE when handling chemicals. PLease PLease read the MSDS's for the chemicals you use. Some chemicals do go straight to the bone such as Hydrochloric acid and will "eat" the calcium in your bones and body. A friend of mine died about 18 years ago while circulating 10% hydrochloric acid solution through a 6000 gallon heat exchanger at a refinery. The hose busted and soaked him because he was not wearing PPE. Once he got to the hospital, he died. An Autopsy revealed his bone mass was greatly dissolved by the chemical. So just be safe out there!!!! We all need to come home to our familieseveryday.