Liquid sodium-potassium alloy

Nuclear and magneto-hydrodynamic electric power generation systems have been produced on a scale which could lead to industrial production, but to-date technical problems, mainly connected with corrosion of the containing materials, has hampered full-scale development. In the case of nuclear power, the proposed fast reactor, which uses fast neutron fission in a small nuclear fuel element, by comparison with fuel rods in thermal neutron reactors, requires a more rapid heat removal than is possible by water cooling, and a liquid sodium-potassium alloy has been used in the development of a near-industrial generator. The fuel container is a vanadium sheath with a niobium outer cladding, since this has a low fast neutron capture cross-section and a low rate of corrosion by the liquid metal coolant. The liquid metal coolant is transported from the fuel to the turbine generating the electric power in stainless steel... 

The same Anal product 175 is obtained in the reaction of spirostiborane 150 with liquid sodium-potassium alloy, most probably via initial one-electron-transfer generating the anion radicals 176a and/or 176b131. ... 

Nowadays this important compound can be easily prepared on a scale up to 200 g when an emulsion of white phosphorus in 1,2-dimethoxyethane is treated vrith liquid sodium-potassium alloy and excess chlorotrimethylsilane is added to the suspension of the hitherto scarcely characterized Zintl phases Na3P and K3P, respectively. With decreasing yield the tris(trimethylsilyl) derivatives of arsane [3], stibane [4], and bismuthane [5] have also been obtained in the same way (Eq. 1). Meanwhile, hesitation to handle dangerous sodium-potassium alloy or white phosphorus led to the development of similar methods to prepare the phosphane [6,7]. 

The needed apparatus and chemicals are placed in the dry box, and the box is closed and thoroughly flushed with dry oxygen-free nitrogen. When in use, it is kept under a small nitrogen pressure so that air will not diffuse into the box. A dish containing phosphorus pentoxide is often placed inside the dry box to ensure that moisture is removed, and if it is particularly important to remove all traces of water and oxygen, a dish containing the liquid sodium-potassium alloy may be placed inside the box. This alloy must, however, be handled with considerable care, for it will bum in air and will react explosively with water. 

The calciner originally built was heated by a heat exchanger using liquid sodium-potassium alloy as a transfer medium which was heated externally in an oil-fired furnace. Although 35,000 hr of satisfactory services were obtained vdth NaK, an in-bed combustion process was developed and installed to obtain a greater processing rate other changes noted were lower vessel wall temperatures, lower ruthenium volatility, and increased reliability. 

Highly dried toluene is the most useful reaction medium. It is obtained according to the following procedure. Pre-dried toluene (over molecular sieve) is refluxed over a liquid sodium/potassium alloy (5-10 ml for 2 1 of toluene) for 4-5 days. An alternative method is the addition of n-butyllithium in small portions (ca. 10 ml for 2 1 toluene) which can be visualized with benzophenone as indicator. When the toluene is sufficiently dried (change of color) it is distilled off and stored under... 

Coolant Liquid sodium potassium alloy (NaK) at 350°C (outlet)... 

Sodium, potassium and sodium-potassium alloys Liquid sodium, potassium or alloys of these elements have little effect on niobium at temperatures up to 1 000°but oxygen contamination of sodium causes an increase in corrosionSodium does not alloy with niobium . In mass transfer tests, niobium exposed to sodium at 600°C exhibited a corrosion rate of approximately 1 mgcm d . However, in hot trapped sodium at 550°C no change of any kind was observed after 1 070 h . 

Iodine was determined by an iodometric titration adapted from White and Secor.(3) Instead of the normal Carius combustion, iodide was separated from the samples either by slurrying in 6M NaOH, or by stirring the sample with liquid sodium-potassium (NaK) alloy, followed by dissolving excess NaK in ethanol. Precipitated plutonium hydroxides were filtered. Iodine was determined in the filtrate by bromine oxidation to iodate in an acetate buffer solution, destruction of the excess bromine with formic acid, acidifying with SO, addition of excess KI solution, and titrating the liberated iodine with standard sodium thiosulfate. The precision of the iodine determination is estimated to be about 5% of the measured value, principally due to incomplete extraction of iodine from the sample. 

Bonilla, C. F., D. L. Sawhuey, and N. M. Makansi, 1962, Vapor Pressure of Alkali Metals III, Rubidium, Cesium, and Sodium-Potassium alloy up to 100 psia, Proc. 1962 High Temperature Liquid MetaI Heat Transfer Tech. Meeting, BNL-756, Brookhaven, NY. (3)... 

In the inter-alkali alloys, eutectic equilibria have been observed in a number of systems very low melting points have been determined for instance in the Rb-Na system (L (Rb) + (Na), at 82.5 at.% Rb and —4.5°C) and even lower melting temperatures have been observed in ternary systems. Binary sodium-potassium alloys, liquid at room temperature (at 25°C in a composition range of about 15-70 at.% Na, about 7-57 mass% Na), have a good thermal conductivity and a wide temperature range where they are liquid they may be used in heat-exchange systems. Their extremely high chemical reactivity must of course be taken into account. 

Bicyclo[4.2.0]octanes wiLh carbonyl groups adjacent to each bridgehead carbon cleave the central bond on reduction with lithium in liquid ammonia,158,159 with sodium/potassium alloy in the presence of chlorotrimethylsilane,160 with zinc in acetic acid,37 or with zinc amalgam in hydrochloric acid.15 7... 

The most commonly used liquid metal is sodium—potassium eutectic. Sodium, potassium, bismuth, lithium, and other sodium—potassium alloys also are used. Mercury, lead, and lead—bismuth eutectic have also been used however, these are all highly toxic and application has thus been restricted. 

The sodium-potassium alloy (45-90 weight %K) is molten at room temperature and cesium melts at 28.5°, so both of these are easily handled as liquids. For example, a hypodermic syringe is convenient for their transfer. The sodium-potassium alloy is made by heating the two metals together while they are protected by a high-molecular-weight hydrocarbon. 

Generally, a heat-transfer fluid should be noncorrosive to carbon steel because of its low cost. Carbon steel may be used with all the organic fluids, and with molten salts up to 450°C (842 °F) [6]. With the sodium-potassium alloys, carbon, and low-alloy steels can be used up to 540°C (1000 F), but above 540°C stainless steels should be used [6]. Stainless steels contain 12 to 30% Cr and 0 to 22% Ni, whereas a steel containing small amoimts of nickel and chromium, typically 1.85% Ni and 0.80% Cr, is referred to as a low alloy steel [6]. Cryogenic fluids require special steels. For example, liquid methane requires steels containing 9% nickel. To aid in the selection of a heat-transfer fluid. Woods [28] has constracted a tenperature-pressure chart for several fluids. 

The metals are employed in a variety of alloys. Lithium generally hardens and strengthens, but also causes embrittlement from 0.05 to 0.1% is used in Al, Zn and Mg alloys. Sodium is an important additive to lead such an alloy is the basis of the manufacture of lead tetraethyl, and another, containing 0.6% Na, 0.6% Ca and 0.05% Li, is a bearing metal. Ternary alloys of caesium with aluminium and either barium or strontium are used in photoelectric cells. Liquid sodium or sodium-potassium alloy is employed to transfer heat from the core of certain atomic reactors, e.g. Dounreay fast breeder. 

Caution. Sodium and particularly potassium react violently with water and may ignite in air. The incrustations of potassium may be explosive only potassium with little or no incrustation should be cut, and care should be taken to ensure anhydrous conditions. Sodium-potassium alloy as well as malodorous tris(trimethylsilyl)phosphine are pyrophoric and extremely sensitive to moisttve. Therefore the entire procedure must be carried out in an atmosphere of dry argon in a well-ventilated fume hood. In case of emergency a sand bath should be available to catch the liquid alloy. 1,2-Dimethoxyethane and tetrahydrofiiran (THF ) may form explosive peroxides. Only fresh, peroxide-free material should be used. 

In the presence of TMS-Cl the enediolate dianion and, importantly, the alkoxide ions, are trapped as their neutral silyl ethers (Scheme 5). This leads to much improved yields of the coupled product the acyloin is isolated in the form of its silyl enediol ether (3). Work-up is much easier. It is only necessary to filter the solution, evaporate the solvent, and isolate the product by distillation or chromatography. The TMS-Cl should be purified by distillation from calcium hydride, under a nitrogen or argon atmosphere, before use. A convenient procedure when using an organic solvent is to add the ester and the TMS-Cl together, dropwise, to the alkali metal finely dispersed in the solvent, at a rate sufficient to maintain the reaction. An explosion has been reported where this procedure was not followed. For a reaction conducted in liquid ammonia the TMS-Cl is added at the end of the reaction and after all the ammonia has been allowed to evaporate. Particularly in cases where sodium-potassium alloy has been used, a pyrophoric residue may have formed, so that the filtration must be carried out under an inert atmosphere. 

A combination of the alternative pathways illustrated in Schemes 13 and 15 explains why the derivative of dimethyl fra 5-cyclohexane-l,2-dicarboxylate (22) fails to give any of the silylated coupled enediol even at 25 °C, using sodium-potassium alloy in benzene, thermal rearrangement to an octa-1,3-diene occurs, whereas use of sodium in liquid ammonia, at -78 °C, cleaves the bond joining the two functionalized carbon atoms, leading to dimethyl 2,7-dimethyloctane-l,8-dioate. ... 

In contrast to the liquid ammonia reaction trisodiumphosphide, Na3P, is the major product resulting from the reaction of white phosphorus (red phosphorus, proved less satisfactory) with sodium potassium alloy or with sodium dispersions in inert organic media (e.g. toluene) at temperatures varying from 80 to 145 °C The phosphide Na3P reacts readily with methyl halides in glyme solvents to afford methylphosphorus compounds in ca. 60% overall yields under optimum... 

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