steve breslin - 2003-08-26

For our purposes there may be two main types of separation: sedimentation and creaming.

There are two parts to a suspension, the continuous phase and the disperse phase. The disperse phase is the material suspended in the continuous phase. An example of this is the snow-globe toy, which you can shake up and suspend the "snow" in the liquid. The glitter-snow is the disperse phase.

I suppose it might be possible to ignore the distinction between disperse and continuous phase, and simply treat the two or more liquids in a suspension equally, and base the separation on their density and that's it. But in case you see a need to complicate this, here's "sedimentation and creaming"....

In the snow-globe toy, the disperse phase settles to the bottom eventually. That's sedimentation.

When the disperse phase is lower in density than the continuous phase, the disperse phase rises to the top of the liquid, or "creams". (Milk is a suspension; the butter or cheese or cream or whatever that rises in milk "creams" -- I guess that's where they got the name from.)

I guess this might be useful if the disperse phase is a non-liquid object. However, if the object is a powder, it can be treated almost the same as a liquid. Once the object is a managable size, it can be treated as a normal object, which suspends (floats midway) in the liquid, floats to the top or sinks.

It's only particles and other liquids where we need to be talking about disperse phases, if we need to use this distinction at all.