Researchers have solved a 123-year old Chemistry mystery by working out how identical forms of a crystalline solid can melt into two distinct liquids. Emil Fischer, an early 20th c. Nobel laureate, produced a crystal that seemed to break the law of thermodynamics, since it melted at two completely different temperatures. Other scientists got the same results with acetaldehyde phenylhydrazone (APH), but nobody could figure out why until recently.