In this screen cast we are going to use a simulation to help explain how to read ternary phase diagrams that you will see in problems whereyou have three components that may or may not be miscible with each other. This does come up when you are doing liquid liquid extraction type work. If you go to this website you willpull up the following simulation. You will see we have component A, that's green, componentB in green and component C in the dark red. There are two main ways we can interpret thesediagrams. When you see these typically the compositions are going to be reported on theaxes such that as you move toward that point you are going to get to 100% of that component.So one way to think about this is if this apex is 100% component A if we are at thatpoint then we draw a line down and at the other end, the line between A and C, we have0%. So any lines perpendicular to the line I've just drawn are going to be our readinglines for component A. So you can see the point we are at right now, if we go acrossfollowing that line, that is going to give us our reading for component A. In this casewe are at 0.31 which you can see up here in the simulation. Following the same logic for100% component C we draw a line downwards from C to get to the line between A and Bwhere we have 0% on that line. And now any lines perpendicular to this line are goingto give us our readings. So if we do that you can see the dashed line that takes usto 0.38 shown here.
So try this with component B. Draw a line away from component B's Apex.We get to 0% B on the line between A and C and any lines perpendicular to this are goingto give us our readings. So you can see, going this way, we get a reading of 0.32 for ourmass fraction of B. So you can play around with this simulation to test yourself andalso see how things change. So as I drag this dot within the diagram, I'm changing the compositionbetween our three components. Of course this does imply that all three components are misciblebecause we have a single phase with this composition. So let's pick a point where we have an equalmass fraction of A, B and C. As you expect, this will fall right in the middle of thistriangle. So we have about 33% of A, B, and C to make it 100% we have a 0.34 mass fractionof A. So if we want it to be 100% A we will be on that apex. If we want 100% C we willbe on that apex and so forth. So if I was dead center at the bottom here, again readingthis way, We get 0.43 mass fraction of B, and reading this way we get 0.1 mass fractionof A and we could either calculate the difference or read off the third axis and see that wehave 0.47 mass fraction of C.
So this is one way to read these ternary diagrams. An alternateto read them is the following with component A. We know the apex up here is 100% A or massfraction 1 and at the bottom is 0. So anywhere in between is going to give us a distanceupwards to component A. And that distance, or that fraction of the total, is our massfraction of A. So one way to interpret is if we have a line that goes from the bottomto the top and that's equal to 1, then this distance from the bottom to this point is0.29 of that full distance. So again, for component C we go to the other line, we drawa straight line, and the distance from zero to that point is a fraction of the whole,in this case its 0.39 so we have 39% of C on a mass basis of a mass fraction of 0.39.We do this for B and this fraction from the base to the point is 31% of the whole or amass fraction of 0.31.
So sometimes you will see the actual numbers within the triangle.So this is one way to interpret the composition at any given point if you are looking at thatdiagram. So let's say we have a mass fraction of C of 0.2. If we want to keep that we moveparallel to that base and what has to change is we increase A, and then our mass fractionof B must decrease, as we see in the simulation. Same thing goes on for A. If we have 50% Awe have to move horizontally to maintain that 50% A. And what changes is the amount of Band C. So hopefully this gives you an idea on how to read these phase diagrams. Do goto the simulation and play around with it. It will definitely help. Thanks.