Fricke solution

The most intensively investigated subject in aqueous solutions is the Fricke dosimeter 10 or 1 mM Fe in 0.4 M H2SO4 because of the clear reaction mechanism and its popularity in radiation chemistry. The dosimeter can be used under aerated and deaerated conditions and their yields of Fe can be expressed by the following equations [44]. 

Another problem that was addressed is to explain how H02 is formed and why its yield is increasing with increase of the LET. Recently, the proposed mechanisms were compared and discussed [55]. 

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The Fricke solution contains iron ion in its constituent, and one might expect the effect of inner-shell photoabsorption of iron around the energy region of the Fe K-shell absorption edge. No photon-energy dependence of the Fricke yield around the K-shell absorption edge of the ion was found, which was explained by the small abundance of iron in the sample. 

Watanabe, R. Usami, N. Kobayashi, K. Oxidation yield of the ferrous ion in a Fricke solution irradiated with monochromatic synchrotron soft X-rays in the 1.8-10 keV region. Int. J. Radiat. Biol. 1995, 68 (2), 113-120. 

Tomita, M. Hieda, K. Watanabe, R. Takakura, K. Usami, N. Kobayashi, K. Hieda, M. Comparison between the yields of DNA strand breaks and ferrous ion oxidation in a Fricke solution induced by monochromatic photons, 2.147-10 keV. Radiat. Res. 1997,148,490 91. 

Dosimetry. The G value for the production of ferric ion in a standard Fricke solution was taken as 15.6 for 60Co y-rays and x-rays produced by primary electron beams with energies of 3 and 14 Mev. Ferric ion was estimated spectrophotometrically in a Beckman DU spectrophotometer using an extinction coefficient of 2197 M"1 cm."1 at 304 m/x at 25°C. 

The Fricke solution has been the most popular subject of ion beam radiation chemistry in aqueous solutions, and proton, helium ions, heavier ions including particle energy higher than GeV [52] and even uranium ions have been employed [53]. Some typical results are shown in Figure 4-1 [54]. The radical yields increase and the water decomposition decreases with increasing the LET of the particles. At a glance, it is clear that the value is strongly dependent on both LET and the kind of particles. 

Tomita, M. Hieda, K. Watanabe, R. Takakura, K. Usami, N. Kobayashi, K. Hieda, M. Comparison between the 5nelds of DNA strand breaks and ferrous ion oxidation in a Fricke solution induced by monochromatic photons, 2.147-10 keV. Radiat. Res. 1997,148,490-491. Maezawa, H. Ito, T. Flieda, K. Kobayashi, K. Ito, A. Mori, T. Suzuki, K. Action spectra for inactivation of dry phage T1 after monoehromatic (150-254 nm) synchrotron irradiation in the presence and absence of photoreactivation and dark repair. Radiat. Res. 1984, 98 (2), 227-233. 

The most well-known liquid chemical dosimeter, the Fricke solution is based on the radiation-induced oxidation of ferrous ions, Fe(II), to ferric ions, Fe(III), in acidic media (E1026 Fricke Reference Standard Dosimeter, ASTM standard). The standard Fricke solution consists of 0.001 mol dm ferrous ammonium sulfate (Fe(NH4)2(S04)2(6H20)), or ferrous sulfate (FeS04(7H20)), and 0.4 mol dm H2SO4 in aerated aqueous solution. It is applicable for measuring doses in the 40 to 400 Gy range. 

The chemical change in the Fricke dosimeter is the oxidation of ferrous ions in acidic aerated solutions. It is prepared from a -1 mM solution of ferrous or fer-roammonium sulfate with 1 mM NaCl in air-saturated 0.4 M H2S04. Addition of the chloride inhibits the oxidation of ferrous ions by organic impurities, so that elaborate reagent purification is not necessary. Nevertheless, the use of redistilled water is recommended for each extensive use. Absorption due to the ferric ion is monitored at its peak -304-305 nm. The dose in the solution is calculated from the formula... 

Growth of Seedlings. Cucumber (Cucumis sativus L., cv. Wisconsin SMR-IS) and soybean (Glycine max L. Merr., cv. Wayne) were grown in vermiculite and watered daily in a controlled environment chamber (26 2 C day, 21 2 C night) on a 12 hr photoperiod (eight 30-W cool-white fluorescent tubes plus four 25-W incandescent bulbs 200+foot-candles). The balanced nutrient solution of Frick and Mohr (H9), modified to include 1 g/1 Ca(N03)2 but without sucrose, succinic acid and kinetin, was applied on alternate days. 

Hydrated electron yields decrease with increasing MZ jE, but they do not seem to decrease to zero. Experiments have been performed on aerated and deaerated Fricke dosimeter solutions using Ni and ions [93]. One half of the difference in the ferric ion yields of these two systems is equal to the H atom yield. The Fricke dosimeter is highly acidic so the electrons are converted to H atoms and to a first approximation the initial H atom yield can be assumed to be zero (see below). There is considerable scatter in the data of the very heavy ions, but they seem to indicate that hydrated electron yields decrease to a lower limit of about 0.1 electron/100 eV. The hydrated electron distribution is wider than that of the other water products because of the delocalization due to solvation. This dispersion probably allows some hydrated electrons to escape the heavy ion track at even the highest value of MZ jE. 

Figure 2 Photon energy dependence of the yield of ssb (open circle) and dsb (closed circle) per absorbed energy in plasmid DNA irradiated in aqueous solution [44]. The Fricke yield is also shown for comparison (closed triangle).

The coolant water at around 300 °C is irradiated mainly at the core of the reactor. At the initial stage to determine the G-values of water decomposition products at elevated temperatures, the Fricke dosimeter was chosen [10-14] because the mechanism of the reaction has been established. Since the reactions in neutral solution are of practical interest, intensive measurement of the G-values of water decomposition products at elevated temperatures in neutral solutions has been done [15 21]. 

Irradiation Conditions and Dosimetry. All irradiations were carried out in the gamma-radiation field of either a nominally 10 or 18 kilocurie cobalt-60 source. Dosimetry of the gamma-radiation field was carried out using the Fricke method (ASTM test D 1671-59). Since the effective mass absorption coefficient for y-rays of this energy is nearly equal for the polymer and for the dosimetric solution, no correction was made for the change in media. 

Let us analyze the following specific reaction [H. Schmalzried, et. al. (1990) T. Frick (1993)]. A single crystal of NiO is used as a solvent for the solid reactants CaO and Ti02, both being moderately soluble in NiO. They isothermally diffuse into NiO from opposite sides (Fig. 9-12 a). Solutes for this type of reaction do not form stable compounds with the solvent crystal, but must form at least one stable compound with each other. 

HPhe Fricke dosimeter (ferrous sulfate solutions) has been used to measure A the radiation intensity of various types of ionizing radiation sources since its development by Fricke and Morse in 1927 (2). It is widely accepted because it yields accurate and reproducible results with a minimum of care. This system meets many of the requirements specified for an ideal dosimeter (5, 9) however, it has a limited dose range, and for our applications it has been necessary to develop a dosimeter covering larger doses. Of the systems reviewed (6, 7), two (ferrous sulfate-cupric sulfate and ceric sulfate) showed the most promise for use with the radiation sources at the U. S. Army Natick Laboratories (8). Of these, the ferrous-cupric system has received the most use, and this paper describes our experience in using this system and suggests procedures by which it may be used by others with equal success. 

NH2)2CO (aq.). The heat of solution of urea was measured by Thomsen,15 Berthelot and Petit,5 Matignon,1 and Walker and Wood.1 Data on the heat of dilution of aqueous urea were reported by Naude,2 Perman and Lovett,1 and Fricke and Havestadt.1... 

KCr(S04)2 nH20 (c). Thomsen15 measured the heat of solution of the dodecahydrate. Kraus, Fricke, and Querengasser1 measured the vapor pressures of the various hydrates over a range of temperature. 

RbAl(S04)2 uH20 (c). For the dodecahydrate we have estimated the heat of solution to be —11. The heats of dissociation of the various hydrates have been calculated from the dissociation pressure data of Kraus, Fricke, and Querengasser1 and Ephraim and Wagner.1... 

Mark G, Schuchmann MN, Schuchmann H-P, von Sonntag C (1990) The photolysis of potassium peroxodisulphate in aqueous solution in the presence of tert-butanol a simple actinometer for 254 nm radiation. J Photochem Photobiol A Chem 55 157-168 Mark G, Korth H-G, Schuchmann H-P, von Sonntag C (1996) The photochemistry of aqueous nitrate revisited. J Photochem Photobiol A Chem 101 89-103 Mark G, Tauber A, Laupert R, Schuchmann H-P, Schulz D, Mues A, von Sonntag C (1998) OH-radical formation by ultrasound in aqueous solution, part II. Terephthalate and Fricke dosimetry and the influence of various conditions on the sonolytic yield. Ultrason Sonochem 5 41-52 MarkG, Schuchmann H-P, von Sonntag C (2000) Formation of peroxynitrite by sonication of aerated water. J Am Chem Soc 122 3781-3782... 

For a selected list of elements (26) there is another acid treatment procedure which is readily applicable to the analysis of orange juice this procedure involves hydrolysis with moderately strong nitric acid to breakdown most of the sugars and to decrease the size of the pulpy constituents. The solution is then filtered, diluted, and measured by atomic absorption. For elements that can be determined with an air-acetylene flame using a high solids (three slot) burner, this procedure offers a useful alternative. Fricke et al. (33) also mentions the utility of this method and gives comparative results on the use of this method in sample preparation. 

R-U-Sb. A NaCl structure type was observed for continuous solid solution Yi HJxSb alloys, x = 0-1, a = 0.6165-0.6208 by using X-ray powder diffraction method (Frick et al.,... 

Only the formation of solid solutions between isotypic compounds has been observed in the R-R -Sb systems. For the /J-U-Sb the formation of both solid solutions (Frick et al 1984) and ternary compounds (Schmidt and Jeitschko, 1998 Slovyanskikh et al., 1990) have been reported. 

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