This standard establishes a reduced molybdenum silicate photometric method for determining the total silicon content in leather. As it is not possible to determine the chemical identity of the siliceous compounds present in leather, the results are expressed in the form of silicon oxide S?O2. The organo-silane compounds existing in leather are also determined by this method. Organosilanes are extracted almost quantitatively from leather with tetrahydrofuran or dichloromethane and this property constitutes the basis of a method that allows their determination (Elliott, JSLTC, 1964, 48, 105; SLTC-Method SLC/16). Therefore, a more reliable estimate of the inorganic compounds containing silicon can be obtained by previously subjecting the leathers, which are assumed to contain organo-silane compounds, to a prior extraction with dichloromethane.