A simple and portable instrument was constructed, based on the energy-dispersive X-ray fluorescence, for the analysis in situ of sulfur in lapideous materials such as frescoes and stone monuments. Sulfur is generally an index of pollution, and the detection of sulfur is of great importance. The instrument for sulfur analysis is characterized by a mini X-ray tube (10 kV, 0.1 mA, Ca-anode) and by a thermoelectrically-cooled Si-PIN detector, of very small dimensions and with an energy resolution of 250 eV, at 5.9 keV. The apparatus was first tested with standard samples, and then employed to measure the S-content of the frescoes of the church of S. Stefano Rotondo in Rome.
