INDEX cation exchange capacity

Soil cation exchangeable capacity is an index used both to evaluate the nutrient and water retention ability of the soil and as an important basis for the amelioration of soil and to apply, rationally, fertiliser. Exchangeable cations absorbed by soil colloid include K+, Na+, Ca2+, Mg2+, Al3+ and H+. K+, Na+, Ca2+ and Mg2+ are exchangeable bases. Al3+ and H+ are exchangeable acids and the sum of these ions is known as the cation exchangeable capacity. Exchangeable Cu2+, Zn2+ and Mn2+ are present at negligible concentrations. 

Worked example 5.9 - cation-exchange capacity and % base saturation One method to measure the CEC of a soil is to leach a column containing a known weight of soil with a solution of a salt so that the exchange sites are saturated with the cation (index ion). After washing out the excess salt solution, a different salt solution is leached through the column and the exchangeable ions displaced, collected in a known volume and their concentration measured. 

Metameric Colours. Colours that appear to be the same under one type of illuminant but, because they have different spectral reflectivity curves, will not match under a different illuminant. Two white vitreous enamels may be metameric, for example, if one is opacified with titania in the anatase form whereas the other contains titania in the form of rutile. Methuselah. A 9-quart wine bottle. Methylene Blue Index A simple approximate method for assessing the surface area of a clay. O.OIM methylene blue dye is added to aqueous suspension of clay, in successive small amounts, to determine the least amount of dye required to impart colour to the water suspending the clay. Dye up to this amount is absorbed by the clay, so that this is a measure of the clay s cation exchange capacity (see ionic exchange). For most pottery clays this is proportional to the surface area to a good approximation. ASTM C837 specifies a test for clays. 

It is well known that corrosion processes are enhanced if there are high levels of impurities in the water. Therefore, to keep the level of impurities low, an ion exchange purification system has been employed since startup in the MIR reactor coohng pool. This system includes a heat exchanger, a pump, two filters with a total capacity of 800 L, a flowmeter, shut-off valves and other fittings. The filters are filled with Russian made nuclear grade ion exchange resins KU-2-8 (cationic) and AV-17-8 (anionic) in the ratio of 2 1. This system provides reduction of the specific p activity by more than a factor of 10. When this index drops to a factor of 2, the resin is replaced otherwise, as a rule, it is replaced once a year. 

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