SULFITE QUANTIFICATION ON DAMAGED STONES AND MORTARS

An analytical procedure was developed for the simultaneous identificat ion and quantification of the sulphite and main anions found in degrad ation patinas on historic buildings and monuments, as well as on stone s and mortars exposed in simulation chamber and field rests. The quant ification of anions was performed by means of ion chromatography (IC), after the stabilisation of sulphite with a D(-) fructose solution. Th e utilisation of two different chromatographic columns, connected in s eries, allowed the simultaneous determination of fluoride, acetate, fo rmate, chloride, nitrite, bromide, iodide, oxyhalides, nitrate, phosph ate, sulphite, sulphate and oxalate, in a time of approximately 25 min , without interference and with high reproducibility. Finally, the res ults show how in the majority of cases the formation of sulphite is an intermediate stage in the sulphation process affecting building mater ials exposed to the environment and needs to be measured together with sulphate, in order to obtain a correct interpretation of degradation mechanisms on such materials. (C) 1998 Published by Elsevier Science L td. All rights reserved.