 Hello, in lesson 5 we will pick up the second part of the separation processes. Remember in lesson 4 we've talked about distillation as perhaps the most significant separation process. In this lesson we will start with the light ends unit. You know that the light ends unit process, the lightest fraction of crude oil, we call it the overhead from the distillation column, ends up as LPG, that is propane and butane, and the NAFTA fractions that are very important for producing gasoline. Now since this is the lightest fraction of crude oil, it's simpler in its molecular makeup, so we can begin actually to see individual compounds. So we can use analytical data, like vapor, liquid, equilibrium, and we could use analytical expressions, equations, like Fansky equations, to make calculations about the separation of these components, like propane, from butane, and so forth. Now distillation is of course one and most important separation process, but there are other processes that would use other physical properties, like the solvent power of compounds, of chemicals. Now one such technique is called solvent extraction. We could use solvent extraction to fractionate the residue that comes from distillation, whether it is atmospheric or vacuum distillation residue. It is more common to have the vacuum distillation residue that goes into the solvent fractionation processes. One important solvent technique is the asphalting, which is done to remove asphalt, the stuff that you put on the road for a route for pavement, and the function, the principle objective of the asphalting is not to make asphalt, really, it is a byproduct, but it is to remove asphalt, so what remains after removing the asphalt from the visit could be used for producing more fuels and other more valuable products in downstream processing. Here you see a sample of asphalt that is produced by the de-assaulting process by rejecting it from the crude oil using the anti-solvent behavior or anti-solvent phenomenon in the de-assaulting process. You can see this is pure asphalt, you need to mix that with aggregates to pave the roads. So the bottom of the barrel is solid form here. Another solvent extraction process is called de-waxing that removes wax. This is the candle wax, the paraffin wax that we know. Again, the purpose here is not to make candle wax, but to remove wax from this heavy fraction of crude oil so that what is left over is a good base stock to make lubricating oils or engine oils.