Potassium metal, liquid alloy

Properties Soft, silvery solid or liquid. (1) 78% potassium, 22% sodium mp -11C, bp 784C, d 0.847 (100C) (2) 56% potassium, 44% sodium mp 19C, bp 825C, d 0.886 (100C). Must be kept away from air and moisture. The liquid forms come under the class name potassium (or sodium) metallic liquid alloy. 

Nickel and nickel-rich alloys must be considered as having generally poor resistance to molten metals. Eldred has made a systematic investigation of the attack of liquid metals on solid metals and alloys, and his results for nickel, and nickel-chromium and nickel-copper alloys, are summarised in Table 7.35. These are for tests at up to 500 C and apart from potassium and sodium all the low-melting-point metals investigated produced moderate to severe attack on the nickel-rich materials. Furthermore, the values for many of the combinations given in the table indicate a marked tendency to preferential intergranular attack. 

Potassium, a soft, low density, silver-colored metal, has high thermal and electrical conductivities, and very low ionization energy. One useful physical property of potassium is that it forms liquid alloys with other alkali metals such as Na, Rb, and Cs. These alloys have very low vapor pressures and melting points. 

The explosion of chloroform in contact with an alkali metal may be demonstrated by means of the apparatus illustrated in Figure 92. About 0.3 gram of sodium or of potassium or of the liquid alloy of the two is introduced into a thin-wall glass tube, or, better yet, is sealed up in a small glass bulb, 6 to 8 mm. in diameter, which has a capillaiy 15 to 20 mm. in length. The tube or bulb containing the alkali metal is placed in the bottom of a narrow test tube into which 1 or 2 cc. of chloroform has already been introduced, and the apparatus is then... 

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. 

The results have been reported of a comparative study of the measured electrical resistivities of liquid alkali metals and alloys, and the theoretical predictions for this quantity obtained within the diffraction model.48 The composition dependence of the Knight shifts in Na-Cs, Na-Rb, K-Rb-Cs, and Na-Rb-Cs liquid alloys has also been examined.49 Addition of small quantities of rubidium (0.3—4.51 atom %) to liquid sodium increases the electrical resistivity almost linearly with increasing solute concentration. With increasing temperature from 100 to 1100 °C, the effect of rubidium on the resistivity of sodium progressively diminishes.50 Addition of the solutes Hg, Tl, and Pb increases the resistivity of liquid potassium linearly with both increasing concentration and temperature. The unit increases in resistivity/pfl cm (atom%) , are 8.80, 9.85, and 15.8 for Hg, Tl, and Pb,... 

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