Chloride concentrations

To maintain charge neutrality, additional halide ions (Cl in our example) have to migrate inside the pit tluis increasing tire local chloride concentration and a chloro-complex is fonned. 

For many metals tire equilibrium lies strongly to tire right hand side. Thus, witliin tire pit tire chloride concentration and tire concentration botli increase, furtlier accelerating metal dissolution. 

A spike recovery for the analysis of chloride in well water was performed by adding 5.00 mb of a 25,000-ppm solution of Ck to a 500-mL volumetric flask and diluting to volume with the sample. Analysis of the sample and the spiked sample resulted in chloride concentrations of 183 ppm and 409 ppm, respectively. Determine the percent recovery of the spike. 

The variation of the dielectric constant of the HCl + H2O mixtures is not appreciably different from that of pure water (78.30) at 25°C until the hydrogen chloride concentration teaches a minimum of 0.2%. It increases slightly over the dielectric constant of water as the concentration increases. 

Tabic 9. Dependence of Solubility of Metal Chlorides on Hydrogen Chloride Concentration in Aqueous Solutions... 

Chlorine. Nearly all chlorine compounds are readily soluble in water. As a result, the major reservoir for this element in Figure 1 is the ocean (5). Chloride, as noted earHer, is naturally present at low levels in rain and snow, especially over and near the oceans. Widespread increases in chloride concentration in mnoff in much of the United States can be attributed to the extensive use of sodium chloride and calcium chloride for deicing of streets and highways. Ref. 19 points out the importance of the increased use of deicing salt as a cause of increased chloride concentrations in streams of the northeastern United States and the role of this factor in the chloride trends in Lake Ontario. Increases in chloride concentration also can occur as a result of disposal of sewage, oil field brines, and various kinds of industrial waste. Thus, chloride concentration trends also can be considered as an index of the alternation of streamwater chemistry by human development in the industrialized sections of the world. Although chlorine is an essential element for animal nutrition, it is of less importance for other life forms. 

Behavior of chloride concentration duriag the period of record was somewhat similar to that of sulfate—about a threefold iacrease compared to the doubliag of sulfate. Data ia Table 1 iadicate that a long-term decrease ia bicarboaate of 10—20 mg/L is a reasoaable estimate. 

The vortex burner maintains stable combustion temperature when the organic concentration ia the waste is sufficiently high and has a heating value of ca 10.5—12.6 MJ/kg (4500—5400 Btu/lb). AuxiUary fuel may be required when the chloride concentration ia the waste exceeds 70% (30). 

Chloride. Chloride is common in freshwater because almost all chloride salts are very soluble in water. Its concentration is generally lO " to 10 M. Chloride can be titrated with mercuric nitrate. Diphenylcarbazone, which forms a purple complex with the excess mercuric ions at pH 2.3—2.8, is used as the indicator. The pH should be controlled to 0.1 pH unit. Bromide and iodide are the principal interferences, whereas chromate, ferric, and sulfite ions interfere at levels greater than 10 mg/L. Chloride can also be deterrnined by a colorimetric method based on the displacement of thiocyanate ion from mercuric thiocyanate by chloride ion. The Hberated SCN reacts with ferric ion to form the colored complex of ferric thiocyanate. The method is suitable for chloride concentrations from 10 to 10 M. 

Ion chromatography can be used to determine chloride concentrations of 2—1000 ppb with a carbonate—bicarbonate eluent (23). Eluoride, nitrite, phosphate, bromide, nitrate, and sulfate do not interfere and can be measured simultaneously with a total analysis time of <30 min. 

A notable example of controlled water reuse was utilization of secondary sewage effluent from the Back River Wastewater Treatment Plant in Baltimore by the Sparrows Point Works of Bethlehem Steel (6). The Sparrows Point plant was suppHed primarily by weUs located near the brackish waters of Baltimore harbor. Increased draft on the weUs had led to saltwater intmsion. Water with chloride concentration as high as 10 mg/L is unsuitable for many steelmaking operations. Rollers, for example, are pitted by such waters. However, treated effluent from the Back River Plant can be used for some operations, such as coke quenching, and >4 x 10 m /d (10 gal/d) are piped 13 km to Sparrows Point. This arrangement has proved economical to both parties for >40 yr. 

Adequate venting of exchangers is required both for proper operation and to reduce corrosion. Improper venting of the water side of exchangers can cause alternate wetting and drying and accompanying chloride concentration, which is particularly destructive to the series 300 stainless steels. 

Anode reactions can be problematic. The anode may dissolve or be oxidized. Or, depending on the pH and the chloride concentration ... 

In sea water with a pH of 8, crevice pH may fall helow 1 and chloride concentration can be many times greater than in the water. The crevice environment becomes more and more corrosive with time as acidic anions concentrate within. Areas immediately adjacent to the crevice receive ever-increasing numbers of electrons from the crevice. Hydroxyl ion formation increases just outside the crevice—locally increasing pH and decreasing attack there (Reaction 2.2). Corrosion inside the crevice becomes more severe with time due to the spontaneous concentration of acidic anion. Accelerating corrosion is referred... 

The amount of chloride, sulfate, thiosulfate, or other aggressive anions dissolved in water necessary to produce noticeable attack depends on many interrelated factors. Extraordinarily, if the water is quite aggressive, general corrosion may occur so rapidly outside the crevice that concentration differences cannot easily develop between the crevice interior and exterior. However, it is usually safe to assume that as the concentration of aggressive anions increases in solution, crevice attack is stimulated. Seawater chloride concentrations produce severe attack in most stainless crevices in a few weeks. 

Calcium carbonate has normal pH and inverse temperature solubilities. Hence, such deposits readily form as pH and water temperature rise. Copper carbonate can form beneath deposit accumulations, producing a friable bluish-white corrosion product (Fig. 4.17). Beneath the carbonate, sparkling, ruby-red cuprous oxide crystals will often be found on copper alloys (Fig. 4.18). The cuprous oxide is friable, as these crystals are small and do not readily cling to one another or other surfaces (Fig. 4.19). If chloride concentrations are high, a white copper chloride corrosion product may be present beneath the cuprous oxide layer. However, experience shows that copper chloride accumulation is usually slight relative to other corrosion product masses in most natural waters. 

Small pits, some the size of pinheads, pockmarked surfaces (Fig. 7.22). Each pit was surrounded by a halo of reddish-brown rust. Cyclic wetting and evaporation caused chloride concentration and increased acidity locally. 

Figure 7.22 Pitting on a 304 stainless steel coupon caused by acidic, chloride-containing water condensating and evaporating. High chloride concentrations were produced locally.

To determine cooling water system flows, use a heat and material balance and a chloride balance (concentration ratio is usually calculated from chloride concentrations). 

E = Cooling system evaporation rate, GPM CR = Cooling system concentration ratio Cr = Chloride concentration in the makeup or blowdown... 

Fast Rinse - Rinsing is carried out to remove excessive brine from the resin. The rinsing operation is generally stopped when the effluent chloride concentration is less than 5-10 ppm in excess of the influent chloride concentration and the hardness is equal to or less than 1 ppm as CaCO. 

Using aqueous ammonium chloride solution, elution was performed by passing through the column 20 liters of eluent in which the concentration of ammonium chloride was continually increased from 0.05 to 1. OM. The unreacted bleomycinic acid was found in the effluent at the ammonium chloride concentration of about 0.05M and NK631 at the ammonium chloride concentration of about 0.45 M. Both fractions, which showed UV absorption at 292 m/u, were separately collected. 

Chloride. The chloride concentration is determined by titration with silver nitrate solution. This causes the chloride to be removed from the solution as AgCl, a white precipitate. The endpoint of the titration is detected using a potassium chromate indicator. The excess Ag present after all Cl" has been removed from solution reacts with the chromate to form Ag CrO, an orange-red precipitate. 

Increasing concentrations of bicarbonate tended to raise the breakdown potentials but also increased the corrosion potentials. This, in combination with a high chloride concentration, high bicarbonate concentrations may raise the corrosion potentials such that they border on passivation breakdown. The increase in hysteresis loop size on potentiodynamic cycles with increasing bicarbonate concentration shows a lowered resistance to pitting attack and crevice corrosion. 

It is in this area that most work has been carried out, particularly in relation to corrosion resistance in sulphuric acid solutionsBourelier etal. and Raicheff etal. investigated the inhibitive effect of chloride ions on corrosion in sulphuric acid. The inhibition efficiency was found to depend on the alloy composition, alloy surface and chloride concentration. The more aggressive the environment, the greater the inhibition efficiency. Yagupol skaya etal studied the effect of iodine additions to sulphuric acid on the corrosion resistance of Ni and Ni-Fe alloys. Again there was an inhibitive effect caused by the halide ion. 

Avoiding situations that increase the chloride concentration — some circumstances in which this can occur in practice are listed below, and it can be seen that control is difficult to ensure. 

The relative proportions of oxygen and chlorine evolved will be dependent upon the chloride concentration, solution pH, overpotential, degree of agitation and nature of the electrode surface, with only a fraction of the current being used to maintain the passive platinum oxide film. This will result in a very low platinum consumption rate. 

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