Tests calcareous/carbonate

Australian Vanadium—Uranium Ore. A calcareous camotite ore at YeeHrrie, AustraHa, is iU-suited for salt roasting and acid leaching. Dissolution of vanadium and uranium by leaching in sodium carbonate solution at elevated temperature and pressure has been tested on a pilot-plant scale... 

As with the calcareous tests, BSi dissolution rates depend on (1) the susceptibility of a particular shell type to dissolution and (2) the degree to which a water mass is undersaturated with respect to opaline silica. Susceptibility to dissolution is related to chemical and physical factors. For example, various trace metals lower the solubility of BSi. (See Table 11.6 for the trace metal composition of siliceous shells.) From the physical perspective, denser shells sink fester. They also tend to have thicker walls and lower surface-area-to-volume ratios, all of which contribute to slower dissolution rates. As with calcivun carbonate, the degree of saturation of seawater with respect to BSi decreases with depth. The greater the thermodynamic driving force for dissolution, the fester the dissolution rate. As shown in Table 16.1, vertical and horizontal segregation of DSi does not significantly coimter the effect of pressure in increasing the saturation concentration DSi. Thus, unlike calcite, there is no deep water that is more thermodynamically favorable for BSi preservation they are all corrosive to BSi. 

Again, there are several choices of extractant, and the preferred one depends mainly on the type of soil under test. One of the most widely used procedures is the Olsen method (Olsen ef al., 1954), which was developed in the USA to correlate crop response to fertilizer on calcareous soils. The amount of P extracted will vary with temperature (increases by 0.43 mg P kg- per degree rise between 20°C and 30°C) and shaking speed, so conditions should be standardized. The extractant is 0.5 M sodium bicarbonate adjusted to pH 8.5. The bicarbonate competes with phosphate on the adsorption sites extracts, and removes most, but not all of it, together with some soluble calcium phosphate. Addition of phosphate-free activated carbon before shaking is necessary if coloured soil extracts are obtained, and then they will require filtration. 

I told you, when we last met, a good deal about carbonic acid. We found, by the lime-water test, that when the vapour from the top of the candle or lamp was received into bottles, and tested by this solution of lime-water (the composition of which I explained to you, and which you can make for yourselves), we had that white opacity which was in fact calcareous matter, like shells and corals, and many of the rocks and minerals in the earth. But I have not yet told you fully and clearly the chemical history of this substance—carbonic acid—as we... 

The strongest support for the involvement of carbonic anhydrase in the regulation of mineral deposition comes from studies on carbonic anhydrase inhibitors. In the presence of inhibitors such as Diamox or sulfanilamide (Fig. 31 )254-260> enzymic activities are strongly reduced and result in a decrease in shell thickness of eggs261 or malformation in calcareous tests of the kind shown in Fig. 32262). In the presence... 

The use of radiocabon as a dating tool depends on the deposition of carbon in the form either of calcareous tests or of organic carbon. The... 

This section primarily focuses on the description of the deposition and accumulation of carbonates in shallow waters and in the deep ocean. The main depocenters for calcium carbonates are the continental shelf areas, as well as island arcs or atolls, which are the typical shallow water environments for massive carbonate formation, and the pelagic deep-sea sediments above the calcite compensation depth catching the rain of small calcareous tests formed by marine plankton in the surface waters. 

EDTA (ethylenediaminetetraacetic acid) extracts of soils tend in general to correlate well with plant contents, in particular with the plant-available fraction for Cd, Cu, Ni, Pb and Zn [208-210], EDTA (0.05 mol at pH 7 was used in the certification of the two soils mentioned above [197]. This test is assumed to extract both carbonate-bound and organically-bound fractions of metals and was hence considered to be suitable for calcareous soil analysis. 

Summary of marine carbonate materials. (From Chaney, R.C. et al.. Determination of calcium carbonate contents in soils. In Geotechnical Properties, Behavior and Performance of Calcareous Soils, Demars, K.R., and Chaney, R.C., eds., Special Technical Publication 777, American Society for Testing and Materials, Philadelphia, PA, pp. 3-15,1982. Reprinted with permission. Copyright ASTM.)... 

Because of the complexity of geomaterials, various databases have been compiled to cross-validate the results of laboratory and in-situ tests, check the reasonableness of theoretical solutions, and allow the development of statistical correlative relationships. These may also be used to help identify problematic soils that offer special difficulties in construction and long-term performance of built infrastructure e.g., organic soils, fibrous peats, calcareous sands, collapsible soils, dispersive clays, loess, carbonates, and loose liquefiable sands and silts. 

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