Reaction of atmospheric pollutants with calcite and marble

Reaction of atmospheric pollutants with calcite and marble 

Deterioration of ancient stonework appears to have accelerated very markedly in many places in the present century Winkler [109], whose treatise on the durability of stone is the major source for the material in this section, shows photographs of early eighteenth century sandstone statues in places close to the Rhine—Ruhr industrial region. After two hundred years, at the beginning of the present century, these statues had clearly delineated features of faces, hands, etc. Sixty years later, they appeared rough outlines, faceless and handless. If this deterioration indeed owes nothing to the military activities of two world wars, it is a remarkable illustration of the effects of industrial pollution of the atmosphere. 

Since the deterioration of stone generally requires water, it might be thought to be essentially a solid—liquid reaction and hence outside the scope of this article. There are, however, many indications that the water for these processes is picked up by the solid from the gas phase, at relative humidities often well below 100%, so that the water is itself a gaseous reactant. 

Quantitative data on stone decay seem rather scarce. Winkler [109] indicates that measurements of the rate of decay were made in Scotland by Sir Archibald Geikie [115] and in New York by Julien [116] in the 1880s and that work of this type was not resumed until after the Second World War. Fundamental knowledge of the kinetics and mechanisms is equally scarce a single paragraph in Winkler s book speculates about possibilities ranging from autocatalytic acceleration to retardation by transport across a product layer, i.e. the usual general topics of solid—gas kinetics, with no detail at all. There seems to be an important field for future work here and another in the matter of gas—solid interaction in the aerosol particles themselves. 

Manning and W.O. Philbrook in J.H. Strassburger (Ed.), Blast Furnace, Theory and Practice, Gordon-Breach, New York, 1969, Chap. XVII. 

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