 And now I'm going to prepare to pH my solution. So this is my pH meter which is here. And this, the important thing to look at on this pH meter is the on and off button that I'm going to turn on. So when I press the on and off button, it brings up whatever you were doing the last time before your pH meter was turned off. And I'm in the measuring mode. That's a mode that you use to measure the pH of solutions. So I don't have to make any other adjustments. And in your lab, most likely your pH meters will be in the measure mode. So what I need to do, this is the pH electrode. This is what I'm going to place into my solution so that I can record the correct pH reading. So I'm going to remove this small container. This actually contains the buffer in which the electrode is stored to keep it safe and to prevent it from corroding. So I wash it. This is water. I'm going to wash it also using my water bottle. So I make sure I wash the pH electrode before I put it in my solution. So that whatever was there will not contaminate my solution. And then I'm going to use chem wipes to gently wipe the electrode. So note I'm using it to gently wipe the outside of the electrode. Don't go into the electrode to wipe it. Just wipe on the outside of it. And then I'm going to put the electrode into my solution. So I make sure I insert it into my solution but not down to the bottom because you do not want it to contact the stir bar because that could damage the electrode. So you put it in and now the pH meter took a reading. It's now at 7.24. So I'm going to actually use sodium hydroxide in order to bring the pH up. Because remember that sodium hydroxide is basic. So if your solution is reading at a pH 7.26 and I want to bring it up to 7.7, that means I have to add sodium hydroxide which is more basic which will bring it up to a higher pH. So now I'm adding my sodium hydroxide. So this is actually one molar sodium hydroxide solution. So I don't want to add too much because it could change my pH to way above what I want. So I add, I'm going to start off by adding one drop to see if it makes a difference. So it's at 7.31. Add two drops. Now it's at 7.38. I'm going to add two more. So you continue doing that adding a drop or two at a time until you get up to 7.77. You don't want to add too many drops at one time because you could go above the 7.7 and then you have to adjust using hydrochloric acid which you don't necessarily want to do because that would alter your buffer that you're making. So I add another drop and another one and if you notice the pH meter is now at 7.71. So I'm just going to add it drop by drop now. It's 7.557.6 between 7.9 and 7.5. So now it's 7.64. I'm going to just add one more drop and now it's at 7.7 exactly. So we have successfully corrected the pH of our PBS solution. So right now we have a solution that is 300 mils PBS and it's at a pH of 7.7. That is how you make up a solution using different ingredients and how subsequently you pH that solution to get the correct pH.