Organic substances which fluoresce are anthracene, fluorescein, and other fused ring structures, used in fluroescent dyes and as tracer materials. The formula weight of a substance is the sum of the atomic masses of all atoms in a formula unit of the substance expressed in amu . Formula unit The smallest unit of an ionically bonded substance. For example, the formula unit of sodium chloride is NaCl. A method of separating volatile mixtures by utilizing the fact that the vapour phase above a liquid mixture is richer in the more volatile component.
Fractionation is the fundamental process for producing petroleum from crude oil.
Gallium arsenide A dark-grey crystalline compound, GaAs, is a material that is used as semiconductors. One of the factors limiting the efficiency of computer chips is the speed with which electrons can move. Through GaAs, electrons move 10 times faster than through silicon -based chips. GaAs chips also have optical properties such as absorbing light to create a current. When a current is supplied, the diode emits light.