Because a new synthetic method produces a mixture of products, it is important to be able to identify and characterize specific solid-state materials. Chemists try changing the stoichiometry to find which stoichiometries will lead to new solid compounds or to solid solutions between known ones. A prime method to characterize the reaction products is powder diffraction, because many solid state reactions will produce polycristalline ingots or powders. Powder diffraction will help the identification of known phases in the mixture. If a pattern is found that is not known in the diffraction data libraries an attempt can be made to index the pattern, that is to identify the symmetry and the size of the unit cell. (If the product is not crystalline the characterization is much more difficult.)