Liquid the distances between the molecules become smaller. When the liquid reaches its freezing point the molecules will usually lock into a very specific order, called crystallizing, and the bonds between them become more rigid, changing the liquid into its solid state (unless supercooling occurs). Only two elements are liquid at standard conditions for temperature and pressure: mercury and bromine. Four more elements have melting points slightly above room temperature: francium, caesium, gallium and rubidium. Metal alloys that are liquid at room temperature include NaK, a sodium-potassium metal alloy, galinstan, a fusible alloy liquid, and some amalgams (alloys involving mercury). Pure
Ionic liquid piston compressor Ionic liquid piston compressor An ionic liquid piston compressor, ionic compressor or ionic liquid piston pump is a hydrogen compressor based on an ionic liquid piston instead of a metal piston as in a piston-metal diaphragm compressor. An ionic liquid compressor takes advantage of two properties of ionic liquids—their virtually non-measurable vapor pressures and large temperature window for the liquid phase—in combination with the low solubility of some gasses ("e.g." hydrogen) in them. This insolubility is exploited by using the body of an ionic liquid to compress hydrogen up to 1000 bar (14,500 psi) in hydrogen filling stations. Linde's ionic