In this screencast we are going to use a simulation to help explain how to read ternary phase
diagrams that you will see in problems where you 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 will pull up the following simulation.
You will see we have component A, that's green, component B in green and component C in the
dark red.
There are two main ways we can interpret these diagrams.
When you see these typically the compositions are going to be reported on the axes 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 that
point then we draw a line down and at the other end, the line between A and C, we have
0%.
So any lines perpendicular to the line I've just drawn are going to be our reading lines
for component A. So you can see the point we are at right now, if we go across following
that line, that is going to give us our reading for component A.
In this case we are at 0.31 which you can see up here in the simulation.
Following the same logic for 100% component C we draw a line downwards from C to get to
the line between A and B where we have 0% on that line.
And now any lines perpendicular to this line are going to give us our readings.
So if we do that you can see the dashed line that takes us to 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 going
to give us our readings.
So you can see, going this way, we get a reading of 0.32 for our mass fraction of B. So you
can play around with this simulation to test yourself and also see how things change.
So as I drag this dot within the diagram, I'm changing the composition between our three
components.
Of course this does imply that all three components are miscible because we have a single phase
with this composition.
So let's pick a point where we have an equal mass fraction of A, B and C. As you expect,
this will fall right in the middle of this triangle.
So we have about 33% of A, B, and C to make it 100% we have a 0.34 mass fraction of A.
So if we want it to be 100% A we will be on that apex.
If we want 100% C we will be on that apex and so forth.
So if I was dead center at the bottom here, again reading this way, We get 0.43 mass fraction
of B, and reading this way we get 0.1 mass fraction of A and we could either calculate
the difference or read off the third axis and see that we have 0.47 mass fraction of
C. So this is one way to read these ternary diagrams.
An alternate to read them is the following with component A.
We know the apex up here is 100% A or mass fraction 1 and at the bottom is 0.
So anywhere in between is going to give us a distance upwards to component A. And that
distance, or that fraction of the total, is our mass fraction of A. So one way to interpret
is if we have a line that goes from the bottom to the top and that's equal to 1, then this
distance from the bottom to this point is 0.29 of that full distance.
So again, for component C we go to the other line, we draw a 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 a
mass 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 that
diagram.
So let's say we have a mass fraction of C of 0.2.
If we want to keep that we move parallel to that base and what has to change is we increase
A, and then our mass fraction of B must decrease, as we see in the simulation.
Same thing goes on for A. If we have 50% A we have to move horizontally to maintain that
50% A. And what changes is the amount of B and C. So hopefully this gives you an idea
on how to read these phase diagrams.
Do go to the simulation and play around with it.
It will definitely help.
Thanks.