text: If the solvent is a solid, then gases, liquids, and solids can be dissolved.
  * Gas in solids:
  ** Hydrogen dissolves rather well in metals, especially in palladium; this is studied as a means of hydrogen storage.
  * Liquid in solid:
  ** Mercury in gold, forming an amalgam
  ** Water in solid salt or sugar, forming moist solids
  ** Hexane in paraffin wax
  ** Polymers containing plasticizers such as phthalate (liquid) in PVC (solid)
  * Solid in solid:
  ** Steel, basically a solution of carbon atoms in a crystalline matrix of iron atoms 
  ** Alloys like bronze and many others
  ** Radium sulfate dissolved in barium sulfate: a true solid solution of Ra in BaSO