Source preparation elements

The difficulties include the inconvenience of handling radioactivity and the necessity for obtaining an accurate radiochemical analysis of two phases containing several elements (which often involves complicated spectra). Highly sensitive instrumentation is required for the analysis e.g. a Li-Si surface barrier detector for a particles, a 2 r gas counter for (3-radiation and a Li-Ge detector for 7-radiation. Great care is required during source preparation, which is best done by electrodeposition. 

A crucial parameter in implanted source preparation is the total implant dose. For on-line work the flux of implant ions is very low as we are far from any stable beam. Even a flux of 106 ions s "1 gives only 1011 ions/day, well below the limiting concentration of order 0.1 atomic percent if implantation is at 50 KeV or above. A valuable feature of OLNO is that a sequence of isotopes may be simultaneously studied as the primary implant decays towards the stability line. This frequently makes accessible isotopes of elements which do not readily form ion beams. 

Element Electronegativity Point (°C) Point (°C) Sources Preparation... 

In England, West et al (1966-1967) studied the same technique. They made use of microwave-excited electrodeless discharge sources, preparing tubes of over 30 elements. They considered a propane flame superior to either the acetylene-oxygen or hydrogen-oxygen flames. The method has been reported to be relatively free of interference effects. 

Long-lived radioisotope analysis is based on the measurement of a very small isotopic ratio. Usually, small amounts of chemically prepared pure samples (in the form of elements or compounds) rather than the original samples are used in the ion source. The element-preconcentration is performed during the preparation of the AMS sample. Since the natural abundances of long-lived radioisotopes are usually very low in terrestrial materials, the contamination by the radioisotope itself from the environment is not a severe problem. The background may come from interferences of atomic and molecular species, stable isobars and isotopes, which can be discriminated effectively by AMS. Consequently, high sensitivities can be achieved in the AMS measurements of the radioisotopes ( °Be, Al, Si, Cl, Ca, etc.) for tracer studies. The... 

The only major bulk chemical not so far considered is phosphoric acid, which can be manufactured pure from phosphorus and in an impure form from phosphate rock. The latter process is the dominant one, the impure product being used mainly in the preparation of fertilizers. Phosphate rock is also the most common source of elemental phosphorus. It is extracted by open-cast mining. The thermal process for producing phosphoric acid from the element produces an acid which is about three times more expensive than that produced direct from phosphate rock using the so-called wet process. 

Halates are readily prepared by the base hydrolysis of the halogen. Bromates and iodates can also be synthesized by the oxidation of the halide. Only iodic acid can be isolated outside of aqueous solution. Chlorates are excellent oxidizing agents, lodate occurs naturally, is a source of elemental iodine, and is a primary standard for iodimetry. The perhalic acids of chlorine and iodine are much easier to prepare than that of bromine. Perchloric acid, like sulfuric and phosphoric acid in previous groups, has a tetrahedral structure around the central atom and involves dir-pir... 

Beryllium is found in some 30 mineral species, the most important of which are bertrandite, beryl, chrysoberyl, and phenacite. Aquamarine and emerald are precious forms of beryl. Beryl and bertrandite are the most important commercial sources of the element and its compounds. Most of the metal is now prepared by reducing beryllium fluoride with magnesium metal. Beryllium metal did not become readily available to industry until 1957. 

The element occurs along with other rare-earth elements in a variety of minerals. Monazite and bastnasite are the two principal commercial sources of the rare-earth metals. It was prepared in relatively pure form in 1931. 

Generally, soluble materials are more effective as micronutrient sources than are insoluble ones. For this reason, many soil minerals that contain the micronutrient elements are ineffective sources for plants. Some principal micronutrient sources and uses are summarized below. In this discussion the term frits refers to a fused, pulverized siUceous material manufactured and marketed commercially for incorporation in fertilizers. Chelates refers to metaHoorganic complexes specially prepared and marketed as especially soluble, highly assimilable sources of micronutrient elements (see CHELATING agents). 

National Institute of Standards and Technology (NIST). The NIST is the source of many of the standards used in chemical and physical analyses in the United States and throughout the world. The standards prepared and distributed by the NIST are used to caUbrate measurement systems and to provide a central basis for uniformity and accuracy of measurement. At present, over 1200 Standard Reference Materials (SRMs) are available and are described by the NIST (15). Included are many steels, nonferrous alloys, high purity metals, primary standards for use in volumetric analysis, microchemical standards, clinical laboratory standards, biological material certified for trace elements, environmental standards, trace element standards, ion-activity standards (for pH and ion-selective electrodes), freezing and melting point standards, colorimetry standards, optical standards, radioactivity standards, particle-size standards, and density standards. Certificates are issued with the standard reference materials showing values for the parameters that have been determined. 

Potassium [7440-09-7] K, is the third, element ia the aLkaU metal series. The name designation for the element is derived from potash, a potassium mineral the symbol from the German name kalium, which comes from the Arabic qili, a plant. The ashes of these plants al qili) were the historical source of potash for preparing fertilisers (qv) or gun powder. Potassium ions, essential to plants and animals, play a key role in carbohydrate metaboHsm in plants. In animals, potassium ions promote glycolysis, Hpolysis, tissue respiration, and the synthesis of proteins (qv) and acetylcholine. Potassium ions are also beheved to function in regulating blood pressure. 

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