Filtration is not the best way to separate liquids unless there is such an obvious difference in the physical properties of each liquid that the one with less density can pass through the filtration system while the denser liquid cannot. In such circumstances, though, the liquids are likely to separate themselves, with the denser one concentrating at the bottom of the container and the less dense one accumulating on the top.
A better way of separating liquids is with a centrifuge, which is a cylinder into which liquids, gasses or other substances are inserted and then spun extremely quickly. The high-speed spinning process forces the different substances -- in this case, the liquids -- to separate according to density. Centrifuges range from relatively simple and inexpensive to extremely sophisticated and very expensive. The better the centrifuge, the better the results one will receive, but for simple experiments, simple centrifuges will suffice.
Another way of separating liquids is through the freezing process. We know that water freezes at 32 degrees Fahrenheit, but many other liquids freeze at higher or lower temperatures. By subjecting the liquids to extremely cold temperatures, they will, again, separate according to density, salinity and other physical properties. If freezing is not an option, then boiling can attain the same results, as, again, liquids of differing physical properties will boil at different temperatures. We know that water boils at 212 degrees Fahrenheit, but other liquids will vary according to their composition.
A mixture can be seperated into pure substances by physical methods. Remember that a pure substance is one with constant composition. One of the most important methods for seperating the components of a mixture is distillation. Distillation is a process that depends on differences in volatility, which is how readily substances become gases. In distillation, a mixture is heated in a device and themost volatile component vaporizes. The most simple forms of distillation include distilling seawater, and separating a mixture of water and sand by boiling off the water.
Another important method is filtration, which uses filter paper when a mixture constist of a solid and liquid. The liquid passes through the paper, and the solid is left behind.
A third method of seperation is called cromatography. The seperation process occurs because the components of the mixture have different affinities for the stationary and mobile phase. The simplest type of cromatogrpahy is paper cromatograhpy.