Chloride ions, impurities

Takenaka, M., Kozuka, S., Hayashi, M., Endo, H. Determination of ultratrace amounts of metallic and chloride ion impurities in organic materials for microelectronics devices after a microwave digestion method. Analyst 122, 129-132 (1997)... 

Impurities in bromine may be deterrnined quantitatively (54). Weighing the residue after evaporation of a bromine sample yields the total nonvolatile matter. After removing the bromine, chloride ion may be deterrnined by titration with mercuric nitrate, and iodide ion by titration with thiosulfate water and organic compounds may be detected by infrared spectroscopy sulfur may be deterrnined turbidimetricaHy as barium sulfate and heavy metals may be deterrnined colorimetricaHy after conversion to sulfides. 

Impurities such as chloride ion or other reducing agents generate chlorine dioxide when the chloric acid solution is heated. Transition-metal ions do not affect the stabiUty of pure chloric acid at room temperature. Thirty-five percent solutions of HCIO have been shown to be stable for 20 days at room temperature containing up to 1000 ppm Ni ", 800 ppm Zn ", 700 ppm Fe ", or 600 ppm Cr " (2). The solubiUty of chloric acid in water is shown in Figure 1. 

Impurities in a corrodent can be good or bad from a corrosion standpoint. An impurity in a stream may act as an inhibitor and actually retard corrosion. However, if this impurity is removed by some process change or improvement, a marked rise in corrosion rates can result. Other impurities, of course, can have very deleterious effec ts on materials. The chloride ion is a good example small amounts of chlorides in a process stream can break down the passive oxide film on stainless steels. The effects of impurities are varied and complex. One must be aware of what they are, how much is present, and where they come from before attempting to recommena a particular material of construction. 

Sodium chlorite [7758-19-2] M 90.4, m 180°(dec). Crystd from hot water and stored in a cool place. Has also been crystd from MeOH by counter-current extraction with liquid ammonia [Curti and Locchi Anal Chem 29 534 1957]. Major impurity is chloride ion can be recrystallised from O.OOIM NaOH. 

The arbitrary division of behaviour has been made because of the extreme behaviour of some chemicals that initiate small areas of attack on a well-passivated metal surface. The form of attack may manifest itself as stress-corrosion cracking, crevice attack or pitting. At certain temperatures and pressures, minute quantities of certain chemicals can result in this form of attack. Chloride ions, in particular, are responsible for many of the failures observed, and it can be present as an impurity in a large number of raw materials. This has led to the development of metals and alloys that can withstand pitting and crevice corrosion, but on the whole these are comparatively expensive. It has become important, therefore, to be able to predict the conditions where more conventional materials may be used. The effect of an increase in concentration on pitting corrosion follows a similar relationship to the Freundlich equation where... 

In the diaphragm-cell process, a solid cathode (iron) is used where hydrogen is evolved [reaction (15.4)]. Porous asbestos diaphragms are used to prevent mixing of the catholyte and anolyte, but owing to the finite permeability of these diaphragms, the alkaline solution that is produced near the cathode stiU contains important levels of chloride ions as an impurity. 

The catalysts had to be free of residual impurities such as chloride ions, nitrates, solvent, or other precursor species. 

Improvement teams, Six-Sigma, 21 174 Impurities. See also Contaminants Metal ion impurities Purification caustic soda in removing, 22 832 in limestone, 15 33, 34t, 40 in magnesium, 15 342-343 in manganese ore, 15 542—545 in metal, 16 130 in MOCVD growth, 22 157 removal in vinyl chloride manufacture, 25 641, 642... 

The quality of the ethanol has a strong influence on its corrosive effects. Three categories of problems have been identified general corrosion (caused by ionic impurities, mainly chloride ions and acetic acid), dry corrosion due to ethanol polarity, and wet corrosion caused by azeotropic water. Corrosion inhibitors should thus be incorporated in ethanol-diesel blends. 

In the first cycle, methanol oxidation peaks are seen in both the anodic and cathodic sweeps around 0.7 V. As mentioned earlier, P -OH formation on Ptdll) does not occur to any substantial extent until 1.2 V. Therefore this current decrease over 0.7 V is not due to deactivation of platinum by the svuface Pt-OH formation. The cxirrent increase on the reversed sweep indicated that this current is not limited by methanol diffusion or active accumulated intermediates, either. It simply seems that platinum loses its catalytic activity over 0.7 V regardless whether platinvim is oxidized or not. Anion effects is not likely the reason because the same phenomena are found in percloric add also. Trace amount of impurities, such as chloride ions, may play some roles. 

Further, the surface segregation of chloride ions, d , has been reported for ionic crystals of NaCl and KCl [Tosi -Doyama, 1966] also, the surface segregation of calcium ions, Ca ", has been reported on ionic ciystals of NaCl to contain caldum impurities [Hummer-Young, 1963]. 

Elemental composition B 9.23%, Cl 90.77%. The compound is slowly hydrolyzed (reaction may he vigorous to violent) and the solution is analyzed for horon hy AA or ICP spectroscopy (see Boron), Also, other metals that may he present as impurities can be measured. The product, HCl in the aqueous solution, resulting from hydrolysis, may he analyzed hy chloride ion-selective... 

This technique is easy to use and its most important merit is that it can readily indicate absence of iodate in case adulterants that give false positive iodometric test are used in its place. The method also enables trace quantities of iodide to be detected even in the presence of large excess of chloride ion. Interferences from impurities normally present in salt were insignificant. 

During the long burial period, extended redistribution of material has taken place. While metal went outwards, ions like chloride and impurities from the environment diffused inwards, resulting in a mass of corrosion products that occupies a volume approximately double the initial size. As a consequence, part of the artifact remains... 

Concomitants Concomitants can be considered impurities present in naturally occurring, nonsynthesized raw materials. They may either present toxic effects, as with arsenic, or be as harmless as chloride ions. An overview of usual concomitants and their limits cited in pharmacopeial compendia are listed in Table 7. 

Impurities, such as water, halides, unreacted organic salts, and organics, easily accumulate in ionic liquids [15] and may influence their solvent properties [3, 16] and/or interfere with the biocatalyst. For example, small amounts of chloride ion caused a severe deactivation of two lipases [17]. The irreproducibility of some early... 

When recrystallizing sulphates, determine the presence of an impurity formed by a chloride ion. 

Rinse sections in high-quality distilled water to remove all traces of chloride ions and other impurities that might contaminate the silver-enhancing solution. Some commercial enhancement solutions are reported to be resistant to contamination, the user should evaluate this carefully, especially if high levels of nonspecific background are encountered... 

Silver chloride is a common source and intermediate product in many extractive metallurgical processes, for example it occurs in the anode slimes from copper refineries, the residues of leaching processes for base metals, as a product of the chlorination of impure gold—silver bullion, and in photographic waste. A novel process for the leaching and purification of silver chloride, which was devised by Parker et a/.,26 is based on the observation that silver chloride is very soluble in some dipolar aprotic solvents containing chloride ion but is much less soluble when water is present. The very different behaviour of the equilibrium... 

The procedure outlined above has many possible sources of both random and systematic error. The measurements of volume and of mass will not be perfectly accurate if the equipment has been correctly calibrated and the laboratory technique is good, these errors are random (equally likely to be positive or negative). The masses of the two nuclei are not perfectly known, but these errors can be assumed to be random as well (the error bars are the results of many careful measurements). The silver chloride and water will both have impurities, which will tend to make systematic errors. Some impurities (e.g., chloride ions in the water) would tend to make the measured solubility product smaller than the true value. Some impurities (e.g., sodium chloride in the silver chloride) would tend to make the measured solubility product larger than the true value. Finally, even without impurities, there is one (probably small) systematic error... 

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