Ferric and manganous ions

However, the ability to act as a builder encompasses much more than so far been mentioned. Builders influence the coagulation of solid soil, often form a buffer system, and promote the soil suspending activity of washing liquors. They are further able to reduce the catalytic effect of ferric and manganic ions. Thus they support the stabilization of peroxides in detergents. Similarly, rancidness caused by catalytic processes of soap and fragrances can be avoided. 

In recent years, the effects of acid rain on lake water, heavy metals contaminated soils and structural materials have been widely discussed (1). Sulfur and nitrogen contained in fossil fuels are released into the atmosphere by combustion. Sulfur and nitrogen oxides dissolve in rain drops as bisulfite, sulfite and nitrite ions. These components are further oxidized into sulfate and nitrate ions. Since these species lower pH, it is important to accurately determine them in rain water. However, these ions are difficult to analyze because they rapidly oxidize in the presence of catalysts such as ferric and manganous ions. Light, temperature, and pH also affect the oxidation rate of S(IV). 

The oxidation of S(IV) is a first order reaction with respect to S(IV) (2,3). This reaction is accelerated by the presence of metallic ions such as ferric and manganous ions which act as catalysts (4-8). Therefore, the effect of the metallic ions on the oxidation of S(IV) was investigated by using test solutions. Table I shows experimental conditions for the oxidation of S(IV) in test solutions. The pH values of synthetic rain water samples were adjusted between 3 and 6. S(IV) concentration in the test solutions was adjusted to 12.5 yM most of S(IV) existed as bisulfite at pH 3-6 (9). The rate of S(IV) oxidation was measured using ion chromatographic analysis. The pH of each test solution was adjusted by using a buffer. 

The result of measurements of the rate constant and half life of S(IV) in the test solutions are shown in Table II. The rate of oxidation of S(IV) in the solution without a catalyst was 0.4-5.9 x 10 3 hr 1. The rate increases by 2 to 4 orders of magnitude in the presence of metallic ions, and a significant catalytic effect of ferric and manganous ions was found in these experiments. In the test solution containing both ferric and manganous ions, the rate enhancement was additive. 

In urban areas like Yokohama, Japan, the concentrations of ferric and manganous ions in rain water are generally in the range of 0.2-2.0 yM and 0.02-0.2 yM respectively, and the pH value of rain water is between 4 and 5. Therefore, a high S(IV) oxidation rate in rain water is expected from the data in Table II. A half life of several minutes to an hour is predicted. Furthermore, S(IV) in rain water is oxidized during sampling, making the measurement of S(IV) in rain water difficult. This fast oxidation rate must be one of the reasons why few reports are found on the measurement of S(IV) in rain water. 

The oxidation reaction of S(IV) in both test solutions and rain water was found to be a first order reaction. Metallic ions such as ferric and manganous ions strongly catalyze the oxidation of S(IV) in rain water. A correlation was found between the concentration of metallic ions and the rate of S(IV) oxidation. The rate constant for the oxidation of S(IV) was found to be 0.12-3.3 hr A (half life ... 

Use oxidation numbers to balance the reaction between ferrous ion, Fe+2, and permanganate ion, MnOr, in acid solution to produce ferric ion, Fe+3, and manganous ion, Mn+2. 

The yeast ADH is very sensitive to various metal ions 1.14 X 10 M Cu", 1.52 X 10 M Kg, and 2.28 X 10 Hg result in 50% inhibition of yeast ADH. Ferric iron and zinc ions were also found to inhibit, but much less so. Ferrous iron and manganous ions did not inhibit at all (von Euler and Adler, 1935). The copper inhibition could be reversed by tenfold excess concentrations of glutathione and cyanide (Wagner-Jaueregg and Moller, 1935). The copper inhibition was confirmed by Negelein and Wulff (1937). It must be kept in mind, however, that the assay system of von Euler and Adler measured oxidation rates of both the flavoproteins and ADH. 

The oxidation of aromatic hydroxylamines with peracids in the presence of cupric ions produces nitroso compounds. In the rigorous absence of metallic ions, azoxy compounds are formed [32]. On the other hand, the air oxidation is strongly accelerated by metals, the approximate order of activity based on a kinetic study being cupric s ferric > manganous > nickel chromic > cobaltous ions. Silver and stannous ions appear to have no effect [33]. 

Although metal ions do not catalyze the decarboxylation of monocarboxylic acids in solution, a variety of metal ions catalyze the decarboxylation of oxaloacetic acid anion, leading to the formation of pyruvic acid (27). The metal ions involved were cupric, zinc, magnesium, aluminum, ferric, ferrous, manganous, and cadmium, approximately 10-2 to 10-3 M (27). Of these, the aluminum, ferric, ferrous, and cupric ions were the most efficient sodium, potassium, and silver ions were inactive. This process involves the decarboxylation of a / -keto acid, which undergoes a relatively facile uncatalyzed decarboxylation. However, not every decarboxylation of a / -keto acid is catalyzed by metal ions—only those... 

Other typical reagents generated for coulometric titrations are hydrogen and hydroxyl ions, redox reagents such as ceric, cuprous, ferrous, chromate, ferric, manganic, stannous, and titanous ions, precipitation reagents such as silver, mercurous, mercuric, and sulfate ions, and complex-formation reagents such as cyanide ion and EDTA [8-10]. 

Figure 6 Effect of electron acceptors on the reduction of arsenate (O) to arsenite ( ) in estuarine sediment slurries incubated (a) without additions, (b) with sulfate ions, (c) with phosphate or manganic ions, and (d) with nitrate or ferric ions. (From Ref. 39.)...

Manganous sulphate5 and ferric salts in general accelerate the decomposition of hydrogen peroxide.6 The sulphate is less active than the chloride or nitrate. With dilute solutions of the salts the effect is proportional to the concentration of the peroxide and that of the iron ions, whilst in the presence of acids it is inversely proportional to the hydrogen-ion concentration. The temperature coefficient of the reaction is 3 25 for ten degrees. ... 

Where two salts that form solid solutions are to be separated, it is far better to use chemical methods of separation where possible. Suppose it were necessary to prepare pure MnS04 7H20 from a quantity of the salt contaminated with ferrous sulfate. Rather than to attempt a direct recrystallization it would be better to dissolve the salt in water, oxidize the ferrous sulfate to ferric by means of chlorine water, neutralize carefully to pH 5 with ammonia to precipitate all the iron as hydrated ferric oxide, and then recrystallize the manganous sulfate. Other separation methods that can be used in such cases are the fractional distillation of volatile compounds and ion exchange both of these methods have been used in separating the rare-earth elements. ... 

IRB are capable of making the environment suitable for SRB. In a mixed population of micro-organisms in a biofilm, as oxygen is consumed, the redox potential starts to decrease so that nitrate, then manganic and ferric ion and the sulphate are reduced [112] this consequence can be seen in Table 4.2. 

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