Clays, chemical analyses

Usual calcination Can be used as temperature, °C calcined aggregate (1450°C- -) or as raw clay Chemical analysis, % Not calcined 1450°C >1750°C... 

Most likely, the chemical system remains closed, as far as the other components in the silicate phases are concerned, as diagenesis or low grade metamorphism becomes more evident. Although there may be transfer of calcium, it seems, from bulk chemical analysis, that there is no systematic increase in potassium nor decrease in sodium content of argillaceous sediments. The transfer of Na and K is between the two size fractions—clay and coarse fraction—or between phyllosilicates and tectosilicates. Albitization of argillaceous rocks should be a common phenomenon where mixed layered phases are predominant in clay assemblages and especially evident in the illite-chlorite zone. 

Trioctahedral clay chlorite is an abundant constituent of soils formed by the weathering of basic volcanic pumice and tuffs in North Wales (Ball,1966). The adjusted chemical analysis (29.35% Si02, 16.82% A1203, 4.42% Fe203, 15.08% FeO, 0.25% MnO, 21.54% MgO, 12.00% H20+, 0.54% H20 ) produces the following structural formula ... 

Kaolinite seldom occurs interstratified with 2 1 clay minerals although Sudo and Hayashi (1956) described a randomly interstratified kaolinite-montmorillonite in acid clay deposits in Japan. On the basis of the chemical analysis (Si02 = 41.94, A1203 = 30.12, Fe203 = 2.42, FeO = 0 21, MgO = 1.52, CaO = 0.32, Ti02 = 0.40, H20+ =... 

Mossbauer spectroscopy may be used for semi-quantitative or qualitative determination of Fe2 /Fe3 ratios Table II shows that a rather good correlation exists between Mossbauer and chemical analysis for Fe2 /Fe3 ratios in clay mineral samples, but these measurements must be obtained at lower temperatures (< 150 K) in order to maximize the recoil-free fractions of both valence states in the sample ... 

It must be recognized that the description of the average chemical formulae by the chemical analysis of clay minerals is not a simple matter. Sheets of the same clay from the same deposit are likely to be heterogeneous with respect to composition and distribution of lattice elements. The charge distribution, as a consequence, is heterogeneous as well. 

Quantum-chemical analysis provides a wide array of powerful tools that have been underutilized in deciphering the complex reactions affecting warfare agents. The computational approach secures development of extensive knowledge of such processes without exposing researchers to their deadly outcome. Therefore, this review is mainly devoted to summarize the results of the theoretical studies of organophosphates interacting with catalytic surfaces (clay minerals and metal oxides). 

Early potters selected materials that were rich in clay, but in some cases, they separated coarser components from the sediments. In other cases, they added temper. In Chapter 4, Bishop and Neff discuss the effect of temper on the chemical analysis of pottery. They point out that the concentration of an element measured in a ceramic artifact can be represented mathematically. Bishop and Neff show that the analysis of pottery sherds... 

In Chapter 5, Olin and Blackman explain that differences in the chemical compositions of pottery are caused by both the use of temper and by chemical and mineralogical differences in the source of the clay. Olin and Blackman report on the continuation of their studies of majolica (a common earthenware pottery) from the Spanish Colonial period in Mexico. They used INAA as well as microscopic examination of the minerals to show that majolica produced in Spain could be distinguished from that produced in Mexico. Volcanic temper was present in the ceramics produced in Mexico, and the chemical analysis of these local ceramics suggested different production centers in Mexico. The discovery of a chemically distinct group of sherds added to the typological classifications of this pottery. 

Any given analyzed sample of pottery is a small subset of a larger ceramic system. Pottery is formed from clays and nonplastic constituents according to shared customs of the local pottery-making group as well as idiosyncratic or stochastic effects. The compositional profile that is derived from the chemical analysis of a ceramic sample, therefore, is a weighted expression of both natural and cultural constraints. 

Thirty-two sherds representing five different examples of Kayenta Anasazi Pueblo II pottery (Tusayan Corrugated [TC], Medicine Black-on-Red [MB], Tusayan Black-on-Red [TB], Dogoszhi Black-on-White [DB], and Sosi Black-on-White [SB]) have been analyzed for the elements As, Ba, Co, Cr, Cm, Fe, Mn, Ni, Pb, Se, V, and Zn by using the techniques of flame atomic absorption spectroscopy (.FAA) and electrothermal atomic absorption spectroscopy (ETAA). Analytical procedures for the chemical analysis of ceramics afford accuracy and sensitivity and require only a modest capital investment for instrumentation. The sherd samples were collected at two sites, one in southern Utah (Navajo Mountain [NM]) and the second in northern Arizona (Klethla Valley [KV]). These sites are approximately 60 km apart. Statistical treatment of the data shows that only three clay types were used in the 32 sherds analyzed, and that only three elements (Fe, Pb, and Ni) are necessary to account for 100% of the dispersion observed within this sample set. 

C. Breen, M. Last Philip, S. Taylor and P. Komadel, Synergic chemical analysis - the coupling of TG with FTIR, MS and GC-MS 2. Catalytic transformation of the gases evolved during the thermal decomposition of HDPE using acid-activated clays, Thermochimica Acta, 363, 93-104 (2000). 

Eight ceramic samples from the Early Jomon occupations at Yagi were also analyzed as part of a continuing project involving both miner-alogical and chemical analysis (30). Basal units at Yagi appeared to have adequate amounts of clay to manufacture pottery, and hence may have... 

Bain, D.C. Smith, B.E.L. (1994) Chemical analysis. In Wilson, M.J. (Ed.) Clay Mineralogy Spectroscopic and Chemical Determinative Methods. London Chapman and Hall, pp. 300-332. 

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