Fig. 12From: Recent progress in instrumental techniques for architectural heritage materialsComparison of the Raman spectra obtained from Sal1 and Sal2 samples. The first efflorescence showed an intense peak due to the potassium nitrate (P.n.), while the major signals of Sal2 are attributed to the presence of sodium sulfate (S.s.) and sodium nitrate (S.n.) [142], copyright (2014) John Wiley and SonsBack to article page