Oxidizable organic matter

In Procedure 11.10, step 1 is designed to extract soluble species, carbonates, and species on exchange sites. Step 2 is designed to extract reducible iron and magnesium oxyhydroxides. Step 3 extracts oxidizable organic matter and sulfides, while step 4 extracts any metals remaining after the completion of the previous extractions. Sequential extraction methods have also been used to extract and quantify the amounts of various arsenic species, primarily as As(III) and As(IV) in soil [21],... 

Here CH2O represents oxidizable organic matter. In reality the reactions with inorganic terminal electron acceptors, particularly Fe(lll) and S04 , should also be considered. But in the absence of a complete understanding of these processes (see Chapter 5), and for the sake of simplicity, we exclude them. 

The stability of solutions of the aminochromes is influenced by many factors such as the nature of the solvent, the pH of the medium, the nature of the buffer used (if any), the presence or absence of dissolved oxygen in the solution, the presence of traces of metal ions, traces of oxidizable organic matter, etc. In general, solutions of the aminochromes with a 3-hydroxyl group [e.g. adrenochrome (1)] are more stable than those without [e.g. epinochrome (27)].106 126,127 On the other hand, solutions of adrenochrome methyl and ethyl ethers were slightly more stable than those of adrenochrome.108... 

Sb, Sn, Ru and readily oxidizable organic matter Ti and readily oxidizable organic matter Difficult to oxidize organic materials Siliceous materials... 

The BOD reaction follows first-order kinetics. The reaction rate is proportional to the amount of oxidizable organic matter remaining at any time. Also, the reaction rate depends on the temperature. The population of microorganisms should be adequately large and stabilized. The BOD value for any incubation period may be theoretically determined from its ultimate BOD and the rate constant for the reaction from the following equation ... 

Trivalent chromium compounds, except for acetate, nitrate, and chromium(III) chloride-hexahydrate salts, are generally insoluble in water. Some hexavalent compounds, such as chromium trioxide (or chromic acid) and the ammonium and alkali metal (e.g., sodium, potassium) salts of chromic acid are readily soluble in water. The alkaline metal (e.g., calcium, strontium) salts of chromic acid are less soluble in water. The zinc and lead salts of chromic acid are practically insoluble in cold water. Chromium(VI) compounds are reduced to chromium(III) in the presence of oxidizable organic matter. However, in natural waters where there is a low concentration of reducing materials, chromium(VI) compounds are more stable (EPA 1984a). For more information on the physical and chemical properties of chromium, see Chapter 3. 

Caution Ionic perchlorate salts are not explosive in general. However, exposure of pure compounds to easily oxidiz organic matter at high temperature greatly increases the risk of fire or explosion (9). 

Eventually, enz5me systems developed that enabled organisms to mediate the reaction of waste-product oxygen with oxidizable organic matter in the sea. Later, this mode of waste-product disposal was utilized by organisms to produce energy by respiration, which is now the mechanism by which nonphotosynthetic organisms... 

Hydrogen sulfide is a commonly occurring decomposition product of organic matter. It is relatively water soluble at higher pHs where it is predominantly dissociated as and S ions. As the pH is decreased below 7, undissociated gas HjS begins to predominate and is released. Since its vapor density is > 1.0, HjS gas tends to settle in low places and creates a toxicity hazard. H S is readily oxidizable by a number of means to less toxic SO3" or 804 forms. 

A fraction of organic C oxidizable with 333 mM KMn04 is another measure of labile organic matter (Blair et al. 1995). This fraction encompasses all those organic components that can be readily oxidized by KMnCL including labile humic material and polysaccharides (Conteh et al. 1999). It commonly accounts for 15-20% of total soil organic C (Blair et al. 1998 Conteh et al. 1998). 

Most oxidation reactions are between specific metal cations or metal oxy-anions and cations. The problem that arises when applying oxidation-reduction reactions to soils is that all soils contain a complex mixture of oxidizable and reducible cations, anions, and organic matter, which means that it is impossible to determine which is being titrated. An exception to this is the oxidation of organic matter where an oxidation-reduction titration is routinely carried out. Organic matter determination will be discussed in Section 10.3. 

Many accidents have been reported involving the preparation and the use of this compound. The compound is sensitive to heat and shock. Reactions with organic matter, finely divided metals and other readily oxidizable substances can be violent to explosive. It is a strong irritant to skin, eyes and mucous membranes. 

Substances Oxidizable by Permanganate (Organic Matter, Nitrites, etc..). I lent lo boiling 100 cc. of tlm water with I re. nl li pvr ccol sulphuric acid, add 1 drop or potassium HiTinnugmmle solution (I KMX)), and main tain the. boiling for Hirer iiiiinilcs. The litpiid should not he decolorised. 

Properties Steel-gray in lumps, black when powdered. Sp, gr. about 4.8. Strong oxidizing agent evolves oxygen when ignited, therefore should not he heated or rubbed with organic matter or oxidizable materials. 

The following is an example of a typical chemical process (in a schematic form) used for the analysis of a wastewater sample in order to determine the presence of organic matter or oxidizable fraction through the measurement of the chemical oxygen demand (COD), a very common parameter in the evaluation of water pollution ... 

Step 3. Extraction of the oxidizable fraction (i.e., organic matter and sulfides) by H2O2 oxidation followed by extraction with NH4(CH3COO)... 

Oxidizable fraction of metals bound to organic matter (leaching with nitric acid and hydrogen peroxide, followed by ammonium acetate)... 

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