The effect of ammonium iron (II)-sulfate hexahydrate [(NH 4 ) 2 Fe (SO 4 ) 2 Á6H 2 O] as a nondurable finish on the flammability of 100% cotton fabric, (woven construction, weighing 144 g/m 2 ) has been investigated. The laundered bone-dried, weighed fabrics are impregnated with suitable concentrations of the above-mentioned salt solution by means of squeeze rolls and drying at 110 C for 30 min. They are then cooled in a desiccator, re-weighed with an analytical balance, and kept under ordinary conditions before the fulfilment of the vertical flame test. The optimum add-on values to impart flame-retardancy expressed in g anhydrous ammonium iron (II)-sulfate hexahydrate per 100 g fabric are about 23.62-25.82%. Thermogravimetric analysis (TGA/DTG) of pure cotton, treated cotton, and the salt is fulfilled and their thermograms are compared and commented. The results are in compliance with 'Gas theory' and 'Chemical theory'.