 We're going to determine the KSP of calcium hydroxide and magnesium hydroxide. We're going to use a pH probe to determine the hydrogen ion concentration solution, which in turn will allow us to calculate the hydroxide ion concentration and in turn the calcium and magnesium ion concentrations. We're going to standardize the pH probe. We're going to take the pH probe out of its storage solution and rinse it with water. We're going to place it into a pH 4 buffer solution. We're going to wait till our CBL reading becomes stable. We're going to press trigger on the CBL and enter a reference value of 4.0 on our calculator. We're going to rinse the probe with distilled water and we're going to then put it into a pH 10 buffer solution. We're going to wait till our CBL reading becomes stable. We're going to press trigger on the CBL and we're going to enter a value. We're going to take the pH probe out of the buffer, rinse it off and put it back in the storage solution. We're now going to read the pH of the calcium hydroxide solution. I'm going to take the pH probe out of the storage solution, rinse it with some distilled water and I'm going to place it into a saturated solution of calcium hydroxide. I'm going to read the pH from the CBL screen. I'm going to rinse off the probe and return it to the storage solution. We're going to take our pH probe out of the storage solution. We're going to put it into a saturated solution of magnesium hydroxide. We're going to read the pH off the CBL. We're going to remove the probe from the solution, rinse it with distilled water and put it back in our storage solution.