ABSTRACT
Infrared spectroscopy is not always thought of as an inorganic analysis tool. It is true that most of the time it is organic molecules whose spectra we are interested in, but many inorganic molecules have useful infrared spectra also. There is no reason why infrared spectra of inorganic materials should not be obtained. Most inorganic substances are found in a crystalline state. Silicon is in the same column of the periodic table as carbon, and forms four bonds in a tetrahedral arrangement like carbon. Organic and inorganic carbonates have the structural unit CO3. In the organic form of carbonates, there is one C=O bond, two C-O bonds, and organic substituents attached to the singly bonded oxygens. Since an inorganic carbonate group is planar, there are out-of-plane and in-plane C-O bending vibrations. The important mid-infrared vibrations of the phosphate group are phosphorous-oxygen stretching and bending vibrations.
