TECHNOLOGY FOCUS - INORGANIC CHEMISTRY - Preferred Composition: The composition is a compound of formula (Na0.5-0.65K0.5-0.35)2S2.4-2.8 or (Na0.6K0.4)2S2.6. In the composition, a maximum of 0.9 mol of alkali metal hydroxide is used per mole of alkali metal hydrogensulfide. The use of the composition is in the presence of aluminum-comprising materials. The use of the composition is in the presence of iron-based materials, where the iron-based materials comprise aluminum (6-28 wt.%) and molybdenum (less than 3 wt.%) and zirconium and/or yttrium (up to 2 wt.%). The composition is a compound of formula (Na0.5-0.65K0.5-4.35)2S2.4-2.8 or (Na0.6K0.4)2S2.6.    TECHNOLOGY FOCUS - POLYMERS - Preferred Components: The alkali metal polysulfides can be obtained by reacting concentrated aqueous solutions of alkali metal hydrogensulfides with sulfur. The alkali metal polysulfides can be obtained by reacting alkali metal hydrogensulfides with a molar excess of alkali metal hydroxides to form alkali metal sulfides mixed with alkali metal hydrogensulfides and reacting these with sulfur to convert them completely into alkali metal polysulfides and, optionally under reduced pressure, distilling off the water at 500 degrees C. The alkali metal polysulfides are prepared by dewatering aqueous solutions of alkali metal hydrogensulfides or aqueous solutions of alkali metal hydrogensulfides which have been reacted with a molar excess of alkali metal hydroxides to form alkali metal sulfides mixed with alkali metal hydrogensulfides, optionally under reduced pressure, and, in a second step, reacting the dewatered alkali metal hydrogensulfides/alkali metal sulfides with liquid sulfur to form the alkali metal polysulfides. Preferred Definitions:    Me1=potassium;and    Me2=sodium;    x=0.5-0.7;    z=2.4-2.9.    EXAMPLE - Sodium hydrogensulfide (2.95 g), and sulfur (1.15 g), the atmospheric oxygen was displaced by argon and the mixture was heated under a blanket of argon from room temperature to 100-130 degrees C. The sulfur melted and the reaction to form polysulfide commenced at the same time. The temperature increased adiabatically within a few seconds to values of 130-150 degrees C. Water mixed with hydrogen sulfide distilled off, and then obtain red liquid composition of Na2S2.8.