Potassium isotopic

Potassium iodide, 20 634 Potassium ions, 20 597, 598, 641 in soap-water system, 22 727 Potassium isotopes, 20 598 Potassium magnesium sulfate, 20 626 Potassium manganate(V), 15 592 Potassium manganate(VI), 15 594-596 Potassium metal, 20 604 production of, 20 600 reducing power of, 20 599 Potassium muds, 9 4 Potassium niobate, 17 152-153 Potassium nitrate, 20 609, 634-636 solubility of, 20 636t uses of, 20 636... 

Jackson SE, Gunther D (2003) The nature and sources of laser induced isotopic fractionation in laser ablation-multicollector-inductively coupled plasma-mass spectrometry. J Anal At Spectrom 18 205-212 Jiang S-J, Houk RS, Stevens MA (1988) Alleviation of overlap interferences for determination of potassium isotope ratios by Inductively-Coupled Plasma Mass Spectrometry. Anal Chem 60 1217-1220 Lam JWH, Horlick G (1990) A comparison of argon and mixed gas plasmas for inductively coupled plasma-mass spectrometry. Spectrochim Acta Part B 45 1313-1325 Langmuir I, Kingdon KH(1925) Thermionic effects caused by vapours of alkali metals. Phil Trans R Soc A107 61-79... 

Alexander CMOD, Grossman JN, Wang J, Zanda B, Bourot-Denise M, Hewins RH (2000) The lack of potassium-isotopic fractionation in Bishunpur chondrules. Meteor Planet Sci 35 859-868 Alexander CMOD, Wang J (2001) Iron isotopes in chondrules implications for the role of evaporation during chondrule formation. Meteor Planet Sci 36 419-428... 

ISOTOPES A total of 18 isotopes of potassium have been discovered so far. Just two of them are stable K-39 makes up 93.2581% of potassium found in the Earth s crust, and K-41 makes up 6.7301% of the remainder of potassium found on Earth. All the other 16 potassium isotopes are unstable and radioactive with relatively short half-lives, and as they decay, they produce beta particles. The exception is K-40, which has a half-life of 1.25x10 years. 

Taylor TI, Urey HC (1938) Fractionation of the lithium and potassium isotopes by chemical exchange with zeohtes, J Chem Phys 6 429 38... 

Srinivasan, G., Sahijpal, S., Ulyanov, A. A. and Goswami, J.N. (1996) Ion microprobe studies of Efremovka CAIs II. Potassium isotope compositions and 41Ca in the early solar system. Geochimica et Cosmochimica Acta, 60, 1823-1835. 

Space does not permit a detailed discussion of the two basic methods used to address these difficulties. In brief, both of them start with measurements of He/ Ne ratios, which provide a measure of the irradiation hardness in metal (but not in stony phases). One method then relies on modeling calculations. Voshage and Hintenberger (1963) used those of Arnold et al. (1961), first to find the conditions needed to reproduce the observed spallogenic " He/ Ne ratios, and then to obtain production rates for the potassium isotopes from estimated cross-sections. As it turned out, the calculated values of N correlate linearly with the " He/ Ne ratios, thereby providing a basis for calculating N for any other iron with a known " He/ Ne ratio. The values of N found in this way range from —1.45 to —1.57. 

They then assembled measured potassium isotope ratios, CF Ar ratios, and " He/ Ne ratios for selected iron meteorites and calculated the values of the parameters a and k that made the " K/K... 

Humayun M. and Clayton R. N. (1995) Potassium isotope cosmochemistry genetic implications of volatile element depletion. Geochim. Cosmochim. Acta 59, 2131-2148. 

Therefore, there exist several of lines of evidence to support the view that impact erosion may have had a significant effect on Earth s composition. However, in most cases the evidence is suggestive rather than strongly compelling. Furthermore, we have a very poor idea of how this is possible without fractionating potassium isotopes (Humayun and Clayton, 1995), unless the entire inventory of potassium is vaporized (O Neill, 1991a,b Halliday et al, 1996 Halliday and Porcelli, 2001). We also do not understand how to lose heavy elements except via hydrodynamic escape of a large protoatmosphere (Hunten et al, 1987 Walker, 1986). Some of the loss may have been from the proto-planets that built the Earth. 

In nature most elements are found as a mixture of isotopes. Usually, no matter where a sample of an element is obtained, the relative abundance of each isotope is constant. For example, in a banana, which is a rich source of potassium, 93.25% of the potassium atoms have 20 neutrons, 6.7302% will have 22 neutrons, and a scant 0.0117% will have 21 neutrons. In another banana, or in a totally different source of potassium, the percentage composition of the potassium isotopes will still be the same. 

As you might expect, the isotopes do differ in mass. Isotopes containing more neutrons have a greater mass. In spite of differences in mass and the number of neutrons, isotopes of an atom have essentially the same chemical behavior. Why Because, as you ll learn in greater detail later in this textbook, chemical behavior is determined by the number of electrons an atom has, not by its number of neutrons and protons. To make it easy to identify each of the various isotopes of an element, chemists add a number after the element s name. The number that is added is called the mass number, and it represents the sum of the number of protons and neutrons in the nucleus. For example, the potassium isotope with 19 protons and 20 neutrons has a mass number of 39 (19 + 20 = 39), and the isotope is called potassium-39. The potassium isotope with 19 protons and 21 neutrons has a mass number of 40 (19 -I- 21 = 40), and is called potassium-40. What is the mass number and name of the potassium isotope with 19 protons and 22 neutrons ... 

Chemists often write out isotopes using a shortened type of notation involving the chemical symbol, atomic number, and mass number, as shown in Figure 4-15. Note that the mass number is written as a superscript to the left of the chemical symbol, and the atomic number is written as a subscript to the left of the chemical symbol. The three potassium isotopes you have just learned... 

The three naturally occurring potassium isotopes are potassium-39, potassium-40, and potassium-41. How do their masses compare Their chemicai properties ... 

As you may know, some common everyday substances are radioactive. In this lab you will investigate the three naturally occurring potassium isotopes found in a common store-bought salt substitute. Two of potassium s isotopes, potassium-39 (93.1%) and potassium-41 (6.89%) are stable. However, potassium-40 (0.01%) decays by beta emission to form stable calcium-40. You will first measure the background radiation level, and then use that information to determine the radiation due to the beta decay of potassium-40. You will also measure radiation at various locations around your school. 

The principal isotope of argon is °Ar (99.6% abundance) it has two other stable isotopes, Ar (0.3%) and Ar (0.1%). Argon-40 is formed by jS-decay of the long-lived potassium isotope see also Noble Gases Ramsay, William Strutt, John. 

Huff GA, Satterfield CN (1984) Intrinsie kineties of the Fiseher-Tropseh synthesis on a reduced fused-magnetite catalyst. Ind Eng in Chem Prod Res Develop 23 851-954 Humayun M, Clayton R (1995) Potassium isotope cosmochemistiy—genetic-implications of volatile element depletion. Geoehim Cosmoehim Acta 59 2131-2148 Igunmov SA (1976) Sulfur isotope exchange between sulfide and sulfate in hydrothermal solutions. Geokhimiya 4 497-503... 

Holness MB (1997) The permeability of non-deforming rock. In Holness MB (ed) Deformation-Enhanced Fluid Transport in the Earth s Cmst and Mantle. Chapman and Hall, London, p 9-39 Humayun M, Clayton RN (1995a) Potassium isotope geochemistry Genetic implications of volatile element depletion. 59 2131-2148... 

The nuclide with the lowest mass for which a Mossbauer resonance has been recorded is °K. This isotope has a natural abundance of 0-012% and is itself radioactive with a half-life = 1-26 X 10 y. The 29-4-keV first excited state is not populated by any radioactive parent, but can be reached during the course of nuclear reactions on the predominant potassium isotope K. Two basic methods have been used a ([Pg.433]

Waste Products and Recycling The natural mixture of potassium isotopes includes approximately 0.012% of the radioactive isotope K, which is both a P-emitter and a y-emitter. Both types of radiation are measured to determine potassium content. 

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