 Okay, so now we're going to talk about how to make a particular buffer. This time you're given the different components of a buffer. So this is a solution and this is an example of a solution that's made up of different components. You have KH2PO4, you have sodium phosphate dibasic, and you have sodium chloride. All of these are going to be combined to give you PBS, and if you notice here, there's a particular pH that you have to make this buffer solution to. The pH here is 7.7. So here you're going to learn about how to actually put your components together to make your solution, and importantly, how to make sure that you have the correct pH of your solution. So if you look in your lab manual, you'll notice that there is a recipe for phosphate buffered saline, that's what PBS means. And this is the recipe here, and this recipe is for one liter of solution. But we're making 300 mils. So we will have to adjust the grams of the different components that we need in order to make our 300 mils of PBS. So if you notice here, for example, we have our potassium phosphate monobasic, and this normally should be 0.2 grams. So you're supposed to add 0.2 grams to water to give you the final volume of one liter. So how much of your potassium phosphate will you need in order to make up your three mils of, 300 mils of PBS? So you do the same cross multiplication like I showed you previously, where you know that you require 0.2 grams of K-H2PO4 in one liter of solution. So how much do you need in 0.3 liters of solution? You do your cross multiplication as shown here, and it gives you the answer here, 0.6 grams. And that is how I calculated how much sodium phosphate diabasic I need and how much sodium chloride I need to give me my final solution of PBS at 300 mils. So that is how you would come up with adjusting the quantity of ingredients that you need to make up a particular buffer.