Emine N. Caner-Saltık

Effect of airborne particle on SO2–calcite reaction

In modern urban atmosphere, sulphur dioxide (SO2) attacks calcite (CaCO3) in calcareous stone-producing gypsum (CaSO4·2H2O) which forms crust at rain sheltered surfaces and accelerates erosion at areas exposed to rain. The airborne particles collected on stone surfaces have always been considered to enhance the gypsum crust formation and thus it is believed that they should be removed from the surface to decrease the effects of SO2. In this study, our aim was to investigate this event by carrying out a series of experiments in laboratory using pure calcium carbonate powder to represent calcareous stone. Sodium montmorillonite, activated carbon, ferric oxide, vanadium pentoxide and cupric chloride were mixed in the pure calcium carbonate powder as substitutes of the airborne particles in the polluted atmosphere. The samples have been exposed at nearly 10 ppmv SO2 concentrations at 90% relative humidity conditions in a reaction chamber for several days. The mineralogical composition of the exposed samples were determined by X-ray diffraction (XRD) analysis and infrared spectrometer (IR). Sulphation reaction products, calcium sulphite hemihydrate, gypsum and unreacted calcite, were determined quantitatively using IR. Exposed samples have also been investigated morphologically using a scanning electron microscope (SEM). Experimental results reveal that calcium sulphite hemihydrate is the main reaction product of the SO2–calcite reaction. It turns out that airborne particles play an important catalytic role in the oxidation of calcium sulphite hemihydrate into gypsum, although their presence does not very significantly affect the extent of sulphation reaction. This behaviour of airborne particles is explained by the presence of liquid film on the calcium carbonate surface where a series of reactions in the gas–liquid–solid interfaces takes place.

Weathering of Dolomite in Industrial Environments

To the exclusion of other major atmospheric pollutants, sulfur dioxide is mainly responsible for attack upon dolomite. This article characterizes Laurel Dolomite on the basis of composition, texture, and porosity; describes the mechanism of the SO2 reaction with dolomite; and develops two equations for the prediction of the rate of decay of dolomite. Over a period of 120 yr nearly 3.57 mm surface reduction at protected areas and 0.915 mm surface reduction at unprotected surfaces of a building in Louisville was calculated. However, these values could not be verified because measurement of these quantities in the field cannot be made.

Raw Material Characteristics and Technological Properties of some Medieval Glazed Ceramics and Tiles in Anatolia

Byzantine and Seljuk cultures are two important overlapping periods in Anatolia during medieval times. Both cultures had special significance in the production of glazed pottery. In architecture, Seljuk culture had further expanded the use of ceramics as glazed tiles in the buildings. The Seljuk glazed tiles were mainly of mosaic and plain tile types. Only monochrome opaque turquoise and monochrome transparent violet-black coloured tiles were examined in this study. The pottery pieces studied represent the deep bowls with fine sgrafitto decorations coming from three archaeological sites namely Ephesus-Byzantine, Iznik-mixed and Korucutepe-Seljuk sites. The potsherds and tiles were analysed to determine the characteristics of body, slip and glaze parts in terms of raw materials composition and firing temperature using various analytical techniques. In addition, the physical properties and the ultrasonic velocity values of the body parts were examined. The results show that tiles are more porous, less dense and have lower ultrasonic velocity values than those of pottery bodies. Tile bodies have moderately vitrified matrix with large sized (~500 μm) particles of quartz added as temper and composed of low-calcareous clay. Temper aggregates do not seem to be used in the potteries.In the tiles, there is no slip between glaze and the body. Monochrome black glaze is alkaline glaze. Manganese and iron are the efficient elements in the development of violet-black tones. The monochrome turquoise glaze is tin-opacified leadalkali glaze, copper being the efficient element in turquoise colour. The potteries were all glazed over a slip having an illitic clay composition together with quartz. Potteries from Ephesus Byzantine site are high lead glazes, while the ones from Korucutepe Seljuk site are lead alkali glazes. Iron is the efficient element in the colouring of yellow, honey and brown coloured glazes while iron and copper are the efficient elements in the colouring of green glazes.