Argon extraction

Figure 14.10—Hydride reactor. Used for some elements, this device includes a mixing tube where the hydride of a metal (or non-metal) is formed by a reaction with sodium borohydride. The flow of argon extracts the metal hydride that is formed (gas separator) and brings it into a quartz tube heated at 800 to 1000 degrees in the flame.

Whetherill, G. W. (1954) Variations in the isotopic abundances of neon and argon extracted from radioactive minerals. Phys. Rev., 96, 679-83. 

The extraction of titanium is still relatively costly first the dioxide Ti02 is converted to the tetrachloride TiCl4 by heating with carbon in a stream of chlorine the tetrachloride is a volatile liquid which can be rendered pure by fractional distillation. The next stage is costly the reduction of the tetrachloride to the metal, with magnesium. must be carried out in a molybdenum-coated iron crucible in an atmospheric of argon at about 1100 K ... 

Use of excess sodium drives the reaction, usually done under an argon or helium blanket, to completion. After cooling, the excess sodium is leached with alcohol and the sodium and potassium fluorides are extracted with water, leaving a mass of metal powder. The metal powder is leached with hydrochloric acid to remove iron contamination from the cmcible. 

Owing to the light and air sensitivity of the carotenoids and retinoids, sample handling is a critical issue. It is recommended to conduct extraction of these materials with peroxide-free solvents, to store biological samples at —70° C under argon and in the dark, to perform the analysis under yellow light, and to use reference compounds of high purity (57). 

Values extracted and in some cases rounded off from those cited in Rabinovich (ed.), Theimophysical Fropeities of Neon, Argon, Krypton and Xenon, Standards Press, Moscow, 1976. This source contains an exhaustive tabulation of values, v = specific volume, mVkg h = specific enthalpy, kj/kg s = specific entropy, kJ/(kg-K). The notation 6.76.—3 signifies 6.76 x 10 . This book was published in English translation by Hemisphere, New York, 1988 (604 pp.). 

Several ion sources are particularly suited for SSIMS. The first produces positive noble gas ions (usually argon) either by electron impact (El) or in a plasma created by a discharge (see Fig. 3.18 in Sect. 3.2.2.). The ions are then extracted from the source region, accelerated to the chosen energy, and focused in an electrostatic ion-optical column. More recently it has been shown that the use of primary polyatomic ions, e. g. SF5, created in FI sources, can enhance the molecular secondary ion yield by several magnitudes [3.4, 3.5]. 

Dihydroxyprecholecalciferol A solution of ia,25-diacetoxyprecholecalciferol (0.712 g, 1.42 mmols), potassium hydroxide (2.0 g, 35.6 mmols) and methanol (40 ml) was stirred at room temperature under argon for 30 hours. The reaction mixture was concentrated under reduced pressure. Water (50 ml) was added to the residue and the mixture was extracted with methylene chloride (3 x 100 ml). The combined organic extracts were washed with saturated sodium chloride solution (3 x 50 ml), dried over anhydrous sodium sulfate, filtered and evaporated under reduced pressure to give 0.619 g of 10f,25-dihydroxyprechole-calciferol asa thick oil. 

M f-BuLi in pentane (14.7 mL, 22 mmol) was added dropwise to a stirred solution of 8 (R = /-Bu 2.63 g, 10 mmol) in anhyd THF (40 mL) at — 80C under an argon atmosphere, and the mixture was stirred at — 80 C for 1 h. After the addition of sublimed sulfur powder (320 mg, 10 mmol), the mixture was allowed to warm to rt over a 2-h period with stirring, and then EtOH (10 mL) was added. The mixture was heated at 55 C with stirring for 2-4 h, poured into ice-water (lOOmL), and then the whole was extracted with Et20 (3 x lOOmL). The combined extract was washed with brine, dried (MgS04), and concentrated in vacuo, and the residue was chromatographed (silica gel, hexane) yield 0.54 g (25%). 

The filtrate is concentrated under reduced pressure with a rotary evaporator until most of the methanol is removed. Extract the aqueous residue with degassed butanol in a separatory funnel, of which the inside has been filled with argon in advance. Evaporate the butanol extract under reduced pressure until most of the water is removed. 

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