Iron concentration

In hydrochloric acid at temperatures up to 100°C, the corrosion rate decreases with time and ferric iron concentration . The presence of air does not affect the general corrosion rate but in IOn acid it promotes pitting attack, which also arises in chloride-containing methanolic solutions in the absence of sufficient water to effect passivation . Alloying niobium with 2.5% or more of tantalum significantly decreases corrosion rates in hydrochloric acid . 

Duncan and Frankenthal report on the effect of pH on the corrosion rate of gold in sulphate solutions in terms of the polarization curves. It was found that the rate of anodic dissolution is independent of pH in such solutions and that the rate controlling mechanism for anodic film formation and oxygen evolution are the same. For the open circuit behaviour of ferric oxide films on a gold substrate in sodium chloride solutions containing low iron concentration it is found that the film oxide is readily transformed to a lower oxidation state with a Fe /Fe ratio corresponding to that of magnetite . 

Fig. 12.1. Effect of iron concentration on yield of citric acid by A. niger.

Iron salts, such as ferrous sulfate or ferrous gluconate, are used in the treatment of iron deficiency anemia, which occurs when there is a loss of iron that is greater than the available iron stored in the body. Iron preparations act by elevating the serum iron concentration, which replenishes hemoglobin and depleted iron stores. 

Iron concentrations are extremely low in these regions (Johnson et al, 1997). The main source is probably particulate iron associated with atmospheric dust (Duce and Tindale,... 

Johnson, K. S., Gordon, R. M. and Coale, K. H. (1997). What controls dissolved iron concentration in the world ocean Mar. Chem. 57,137-161. 

Figure 1.4a. Iron concentration in raw and cooked foods. For braked foods, comparisons are between dough and baked product. For stew ingredients, raw foods are compared to foods cooked together in an iron pot.

Park, C.H. and Recknagel, R.O. (1983b). Hepatic lipid peroxidation in vivo in rats with chronic dietary overload is dependent on hepatic iron concentration. Trans. Assoc. Am. Physicians 96, 146-154. 

Iron concentrations expressed as negative log of Fe(IlI) buffered by HEDTA. Plants grown at pFe I6..S were green, whereas those grown at increasingly lower iron concentrations became increasingly chlorotic. 

High iron concentrations may result in fouling when conditions alter the valence state and convert soluble species to insoluble species. 

Iron transport agents may belong to the protein or non-protein class. In the former group are found the animal proteins transferrin (25), lactoferrin (26) and conalbumin (27). The low molecular weight iron carrying compounds from microorganisms, the siderochromes, may occur with or without a bound metal ion. Typically, severe repression of biosynthesis of these substances can be expected to set in at an iron concentration of ca. 2 x 10-5 g atoms/liter (28). Most, but not all, of these substances can be described as phenolates or hydroxamates (4). 

Walsh, K., G. J. Jones et al. (1998). Effects of high irradiance and iron concentration on pigment and fatty acid composition in the cyanobacterium Microcystis aeruginosa. Mar. Freshwater Res. 49(5) 399 107. 

Schneider, 1984 Schneider and Schwyn, 1987 Schneider, 1988 Cornell et al., 1989). Perchlorate solutions that contain the dinuclear Fe2(OH)24+ to about 10 % of the total iron concentration can be kept unchanged for several weeks. This is by no means trivial, because it was recognized many years ago that solutions containing Fe2(OH)24+ to a significant degree are supersaturated with respect to solid phases such as FeO(OH) (Biedermann and Schindler, 1957). The low molecular species interact to produce species with a higher nuclearity (equation 7) ... 

Recently, another interaction was reported between an intracellular pathogen and the key regulator system of intracellular iron concentration, i.e. the degree of binding of the IRPs to IRE (see Chapter 7). In extracts from Leishmania tarentolae, a protein has been detected that binds specifically to the mammalian IRE. However, the exact nature and function of this protein is unclear up to now. In contrast to mammalian IRPs, the L. tarentolae IRE-binding activity was not induced by growth in iron-depleted medium (Meehan et ah, 2000). 

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