Chlorides buried

The principal sources of dissolved chloride in the more saline fluids of sedimentary basins include dissolved chloride buried at the time of sediment deposition, chloride derived by refluxing of subaerially evaporated surface brines, chloride derived from subsurface mineral dissolution, principally halite, and marine aerosols. The Cl-Br systematics of sedimentary brines provide useful constraints on interpreting the origin of chloride in these waters (Carpenter, 1978 Kharaka et al., 1987 Kesler et al., 1996). 

A relatively simple method is to dissolve out the chloride ions by immersion in a suitable solvent. Water has been used with the water being changed every month until no further chlorides are detected. This can take up to 5 years for marine artefacts with high levels of chloride buried within deep rust layers. Moreover, the metal will continue to corrode, while the artefact is immersed in the water for this length of time. By altering the pH of the solution it may be possible to dissolve out the chlorides without corroding the metal. This is achieved by forming a thin, passive film approximately 10 nm ( 10 9m) thick... 

The principle of this method of conservation is to immerse the artefact in a tank containing a suitable solution. The chloride ion dissolves from the rust him into the solution that is changed, initially, every week and subsequently every month. The chloride content of the solution is analyzed at the end of each changeover. The process is continued until there is no more chloride detected. At this point, the artefact is deemed to be conserved. This can take up to 5 years for marine artefacts with high levels of chlorides buried within deep rust layers. Even after this length of time, one is not absolutely certain that all the deleterious ions have been removed from the rust/metal interface. 

Stainless steels have not been widely used in applications where they are buried in soil, but some applications have involved underground service. Various stainless steels from the 13% Cr to the molybdenum-bearing austenitic types were included in the comprehensive series of tests in a variety of soils reported by Romanoff . High-chloride poorly-aerated soils proved most aggressive, but even here the austenitic types proved superior to the other metals commonly used unprotected. Of special interest is the fact that though corrosion was by pitting there was little or no increase in pit depth after the first few years. 

Galvanised steelwork buried in the soil in the form of service pipes or structural steelwork withstands attack better than bare steel, except when the soil is more alkaline than pH 9-4 or more acid than pH 2-6. Poorly aerated soils are corrosive to zinc, although they do not necessarily cause pitting. However, soils with fair to good aeration containing high concentrations of chlorides and sulphates may do so. Bare iron may be attacked five... 

The consumption rate of HSI anodes buried directly in soils will vary depending upon the soil composition and will be excessive in chloride-containing soils. In quicksands consumption rates of approximately 0-35 kg A y have been reported, whilst in other soils consumption rates in the region of 1 kg A y... 

Thermoplastic resins, such as vinyl chlorides, vinyl acetates and polyamides are employed, particularly in the water industry, on buried pipes and fittings. To provide both internal and external coating, application may be by one of these principle techniques dipping in a plastisol, fluidised beds or electrostatic spray. 

Bury, C. R. Davies, E. R. H. (1932). System magnesium oxide-magnesium chloride-water. Journal of the Chemical Society, 2008-15. 

Most corrosion processes in copper and copper alloys generally start at the surface layer of the metal or alloy. When exposed to the atmosphere at ambient temperature, the surface reacts with oxygen, water, carbon dioxide, and air pollutants in buried objects the surface layer reacts with the components of the soil and with soil pollutants. In either case it gradually acquires a more or less thick patina under which the metallic core of an object may remain substantially unchanged. At particular sites, however, the corrosion processes may penetrate beyond the surface, and buried objects in particular may become severely corroded. At times, only extremely small remains of the original metal or alloy may be left underneath the corrosion layers. Very small amounts of active ions in the soil, such as chloride and nitrate under moist conditions, for example, may result, first in the corrosion of the surface layer and eventually, of the entire object. The process usually starts when surface atoms of the metal react with, say, chloride ions in the groundwater and form compounds of copper and chlorine, mainly cuprous chloride, cupric chloride, and/or hydrated cupric chloride. 

Bury, N.R., F. Galvez, and C.M. Wood. 1999a. Effects of chloride, calcium, and dissolved organic carbon on silver toxicity comparison between rainbow trout and fathead minnows. Environ. Toxicol. Chem. 18 56-62. 

ISO/TR 7073 1988 Recommended techniques for the installation of unplasticized poly (vinyl chloride) (PVC-U) buried drains and sewers ISO 7387-1 1983 Adhesives with solvents for assembly of PVC-U pipe elements -Characterization - Part 1 Basic test methods ISO 7508 1985 Unplasticized polyvinyl chloride (PVC-U) valves for pipes under pressure -Basic dimensions - Metric series... 

What has happened to the bicarbonate and calcium delivered to the ocean by river runoff As described later, these two ions are removed from seawater by calcareous plankton because a significant fraction of their hard parts are buried in the sediment. In contrast, the only sedimentary way out of the ocean for chloride is as burial in pore waters or precipitation of evaporites. The story with sodium is more complicated— removal also occurs via hydrothermal uptake and cation exchange. Because the major ions are removed from seawater by different pathways, they experience different degrees of retention in seawater and uptake into the sediments. Another level of fractionation occurs when the oceanic crust and its overlying sediments move through the rock cycle as some of the subducted material is remelted in the mantle and some is uplifted onto the continents. 

We must not overlook, however, the fact that when the field of a polar bond is sufficiently buried within the molecule its influence upon solubility tends to disappear. Thus, in spite of the polarity of the bond between the carbon atom and the nitro-group, as shown in nitrobenzene and nitromethane, we might expect tetranitromethane to behave in its solutions as a substance of low polarity. Again, stannic chloride is nonpolar but stannic fluoride, apparently on account of the smaller halogen atoms, is so polar as to form a high-melting solid. 

Silver is another native metal found in museum collections in a variety of forms. Chemically, silver differs gready from gold in that it is highly reactive. Silver occurs in its native state, but is more stable in compounds with other elements. The black tarnish so common on silver items is silver sulfide. Silver objects that have been buried for any length of time may be completely altered, particularly if water is present. When the alteration that begins as tarnish is complete, and all native silver has been combined with other elements, a worked piece will usually lose its integrity and disintegrate. If silver is subjected to moisture in the presence of the element chlorine, as it would in seawater or brackish water, horn silver or silver chloride may develop. 

Fig. 5.19 Arrangement for test of sympathetic detonation for dynamite in vinyl chloride tube buried in the sand...

LONG TERM BEHAVIOUR OF POLY(VINYL CHLORIDE) PRODUCTS UNDER SOIL BURIED AND LANDFILL CONDITIONS... 

Although bacteriorhodopsin contains all of the buried arginine residues which could possibly play a role in binding anions in halorhodopsin, its absorption does not show anion-dependent effects except at very low pH where protonation of asp85 (with a pK of 2.5) causes a shift from 568 nm to about 605 nm [22,56-63]. Addition of chloride to this blue chromophore shifts the maximum back to 565 nm [56,61,64-66]. A sustained photocurrent was not seen at the low pH, but after addition of chloride the photocurrent reappeared. It is tempting to compare these chloride-dependent effects to the behavior of halorhodopsin the possibility of chloride transport by bacteriorhodopsin at low pH was mentioned [67,68]. However, there are discrepancies. Chloride in halorhodopsin causes a red-shift rather than a blue-shift, and the photocycle of bacteriorhodopsin at low pH with bound chloride is quite different from the photocycle of halorhodopsin with bound chloride [61]. 

The wearer. should be a.ssi.sted by another man wearing Imth gas mask and prote< (ive gloves. DUcarded contamiimted clothing should be buried in a pit and coveretl with chloride of lime and earth. 

Bromine is too reactive to exist as a free element in nature. Instead, it occurs in compounds, the most common of which are sodium bromide (NaBr) and potassium bromide (KBr). These compounds are found in seawater and underground salt beds. These salt beds were formed in regions where oceans once covered the land. When the oceans evaporated (dried up), salts were left behind—primarily sodium chloride (NaCl), potassium chloride (KCl), and sodium and potassium bromide. Later, movements of Earth s crust buried the salt deposits. Now they are buried miles underground. The salts are brought to the surface in much the same way that coal is mined. 

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