Outlines of English and American Literature: an Introduction to the Chief Writers of England and America, to the Books They Wrote, and to the Times in Which They Lived by Long, William Joseph, 1866-1952 - Free ebook download as Text File (.txt), PDF File (.pdf) or read book online for free. Name; udp://tracker.opentrackr.org:1337/announce: udp://tracker.zer0day.to:1337/announce: udp://tracker.coppersurfer.tk:6969/announce: udp://tracker.leechers-paradise. Free iron is one of the major analytical items for soil basic properties. It is also an important indicator for understanding the genesis of soil, soil classification, and soil distribution behavior. In this study, an alternative analytical method (chemisorption) based on thermodynamic knowledge was proposed for measurement of total free iron oxides in soils. Several representative soil samples belonging to alfisols, ultisols, inceptisols, and entisols were collected from Taiwan and tested by the chemisorption, and the estimated total free iron oxides were compared with those measured from the traditional citrate bicarbonate dithionite (CBD) method. Experimental results showed that the optimal operating temperature was found to be at 773 K and the carbon monoxide (CO) is the best gaseous reagent to promote the formation of FeS. ![]() The estimated total free iron oxides for soil samples determined from the chemisorption in the presence of CO were very close to those from the CBD technique. The result of regression indicates that the estimated total free iron is strongly correlated with the CBD-Fe content ( R 2 = 0.999) in the presence of CO. Introduction Iron is the third greatest metal element in soils. The iron content in soils may vary between one and several hundred grams per kilogram depending on the type of parent materials. There are sixteen iron oxides, oxide hydroxides, and hydroxides known in the environment to date. Among these iron oxides, Fe 2O 3 ( α and γ form), Fe 3O 4, and FeOOH ( α and γ form) are of interest and attracted the greatest amount of attention due to their well distribution in soils and industries. Hematite, α-Fe 2O 3, is the oldest known iron oxide and is widespread in soils and rocks. Hematite consists of layers of octahedral FeO 6, which are connected by edge and are face-sharing and stacked perpendicular to c direction. Magnetite, Fe 3O 4, is one of the spinel structural groups. This type of iron oxide differs from most other iron oxides in that it contains both divalent iron and trivalent iron. Its formula is written as Y[XY]O 4, where X = Fe(II), Y = Fe(III), and the brackets denote octahedral sites. The structure consists of octahedral and mixed tetrahedral/octahedral layers stacked along (1,1,1) direction. Goethite, α-FeOOH, consists of an HCP array of O 2− and OH − stacked along the (1,0,0) direction with Fe(III) ions occupying half the octahedral interstices within a layer. It is the most common iron oxide in soils due to its high thermodynamic stability. Lepidocrocite, γ-FeOOH, is a layered compound. The structure consists of arrays of CCP anions (O 2−/OH −) stacked along the (0,5,1) direction with Fe(III) ions occupying the octahedral interstices. Like goethite, lepidocrocite consists of double chains of Fe(O,OH) 6 octahedral running parallel to the c-axis. In soil science, iron species can be generally classified into several groups, including organically bounding iron, amorphous iron, free iron, and total iron. Free iron is defined as the iron coated/adsorbed on the surface of soil but not counting in the lattice structure of the soil. For the basic soil analysis, free iron is the major analytical item because it is an important indicator for understanding the genesis of soil, soil classification, and soil distribution behavior [, ]. Ppsspp game files download. For example, the ratio of the amorphous iron and free iron is an important indicator to distinguish the weathering extent of soil horizon. Deb was among the first to use sodium dithionite to measure the free iron oxide content of soils []. More recently, a series of modified procedures were presented and reported in the past decade [–]. Among the reported extraction procedures, the citrate bicarbonate dithionite (CBD) method has been recognized as the most commonly used procedure for determination of total free iron oxides in soils or sediments []. Additionally, hematite, goethite, lepidocrocite, ferrihydrite, and noncrystalline iron as well as organic-complexed iron can be exacted by the CBD procedure. Unfortunately, the high sodium salt content in the CBD extracts not only causes severe carry-over effect but also tends to clog the burner head during atomic absorption spectrometry (AAS) analysis. Aspiration of deionized water or dilute acids for a longer period between samples is thus needed for accurate analysis. To overcome these shortcomings, an alternative analyzed method was developed and assessed for the determination of total free iron contents of soils in this study. On the other hand, a series of the reactions between iron oxides and H 2S were experimentally performed at high temperature and results showed that the high reactivity between iron oxides and H 2S was observed in our previous literatures [–].
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