Carbonic acid aggressiveness

Additionally, potable water should not exceed pH values of 9.5 or fall below pH values of 6.5. 

Consider these technical requirements when checking if the potable water extracted from the drinking water well B3 in the model area (chapter 3.1.1.1, Fig. 40) can be used without further treatment. 

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The corrosion of lead in natural waters depends on the hardness of the waters, as evidenced by the data in Table 4.56. The natural waters of moderate hardness (i.e., less than 125 ppm calcium carbonate) tend to be less aggressive due to the formation of a protective film, which is also aided by the presence of silicates. On the other hand, nitrate ions disrupt the protective film and increase the corrosion rate. Corrosion of lead occurs in waters containing carbonic acid due to the conversion of carbonate in the film into... 

Archaean weathering profiles. Further evidence for a C02-rich Archaean atmosphere comes from indications of an aggressive weathering regime in the late Archaean sedimentary record, driven by a high content of carbonic acid in the weathering environment. Two different arguments are used to support this claim. First, first-cycle sediments are much more refractory than their modern... 

I mentioned an example of how CO2 becomes concentrated in steam systems (see Fig. 12.6). Anytime CO2 starts to dissolve in water, carbonic acid will form, which has a relatively high pH as compared to other common minerals acids (sulfuric, hydrochloric, nitric acid). Actually, carbonic acid is aggressively corrosive to carbon steel at a pH of 5.5. Sulfuric acid at a pH of 5.5 is otrly mildly corrosive to carbon steel. 

Higher acidity caused greater corrosion but contamination by sulphur dioxide or carbon dioxide inhibited attack. By contrast, chloride ions were found to have a mild aggressive effect. 

Rainwater is essentially free of mineral solutes. It is usually slightly acidic due to the presence of dissolved carbon dioxide, or more highly acidic because of acid rain-forming constituents. As a result of its slight acidity and lack of alkalinity and dissolved calcium salts, rainwater is chemically aggressive toward some kinds of mineral matter, which it breaks down by a process called chemical weathering. 

Obtained carbon materials are characterized by high stability at increased temperatures (temperature of testing should not exceed the temperature at which the material is produced, though), as well as in humid and aggressive (acidic and alkaline) media and under hyperbaric conditions. 

Boron-doped diamond is electrically conducting and has found applications as electrode material in waste-water treatment, ozone generation, electroanalysis, and trace metal detection [ii]. Due to their exceptional chemical inertness and mechanical strength, diamond electrodes have been proposed for applications in extremely aggressive media such as strong acids or plasmas. See also -> carbon electrodes. 

Normally, nitration of deactivated compounds (and therefore polynitration of toluene) is carried out using aggressive nitric acid - oleum mixtures. Dinitration of toluene with mixed acids produces a 4 1 ratio of 2,4- and 2,6-dinitrotoluenes, from which the former is isolated for manufacture of toluenediisocyanate (TDI) and toluenediamine, both of which are used in the manufacture of polyurethanes. Zirconium and hafnium derivatives catalyse nitration of o-nitrotoluene, but ratios of 2,4- 2,6-dinitrotoluene are modest (66 34).12 Dinitration of toluene using Claycop (copper nitrate on K10 clay), acetic anhydride and nitric acid in the presence of carbon tetrachloride produced dinitrotoluenes in a yield of 85% with a ratio of 2,4- 2,6-dinitrotoluene of 9 1.13 This method, however, requires a large excess of nitric acid, the use of an unacceptable solvent and long reaction times. The direct nitration of toluene to 2,4-dinitrotoluene using nitric acid over a zeolite P catalyst, with azeotropic removal of water, is reported to give a 2,4 2,6 ratio of 14, but full results are yet to be published.14... 

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