Now, the second thing you need to use is called an acid based indicator. Acid based indicators are compounds that change color in solution when they convert to their conjugate acid based form. Now, what you do is you take your indicator, you take a very small amount of it and you place it into your solution before you begin saturation. And what the indicator does, it reacts with the H plus ions in the following way. When there is a lot of H plus ions associated in our solution, aka, when it's acidic, that means equilibrium will shift this way. Now, when there is very little H plus ions or our concentration of H plus ion is very low, equilibrium will shift this way.