All these bands indicate that wool fiber is made of the complex polyamide chains that are formed from the carboxylic group and the amino group of different amino acids by crosslinking. The S-O stretching bands near 1040 cm_1 may result from the oxidation step in the chlorine-Hercosett treatment for wool fabric. When the fabric was coated with the silica, several very pronounced bands appeared at 1100, 930 and 790 cm_1.