Techniques useful for the separation of mixtures include the following:
DISTILLATION is the purification of a liquid by heating it to its boiling point, causing
vaporization, and then condensing the vapors into the liquid state and collecting the
liquid. Separation of two or more liquids requires that they have different boiling
temperatures. All boiling temperatures can be reduced by decreasing the pressure
on the liquid.
EXTRACTION is the removal of one substance from a mixture because of its
greater solubility in a given solvent.
FILTRATION is the process of removing or "straining" a solid (the chemical term is
precipitate) from a liquid by the use of filter paper or other porous material.
DECANTING is the pouring of a liquid from a solid-liquid mixture, leaving the solid
behind.
CENTRIFUGING is the process of separating a suspended solid from a liquid by
whirling the mixture at high speed.
SUBLIMATION is the physical property of some substances to pass directly from
the solid state to the gaseous state without the appearance of the liquid state. Not
all substances possess this characteristic. If one component of a mixture
sublimates, this property may be used to separate it from the other components of
the mixture. Iodine (I2), naphthalene (C10H8, mothballs), ammonium chloride
(NH4Cl) and dry ice (solid CO2) are some substances which sublime.
CHROMATOGRAPHY is the process of separating a mixture by the distribution of
its components between two phases, one phase being stationary and the other
phase moving. Some examples of chromatography are gas chromatography, paper
chromatography, and thin-layer chromatography.
