---
title: The Mysterious Crystal That Melts at Two Different Temperatures
description: 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.
---

[Fluid Systems Engineering & Management Blog | Swagelok NorCal ](https://northerncal.swagelok.com/blog)

# [The Mysterious Crystal That Melts at Two Different Temperatures](https://northerncal.swagelok.com/blog/the-mysterious-crystal-that-melts-at-two-different-temperatures)

 Written by [Jeff Hopkins](https://northerncal.swagelok.com/blog/author/jeff-hopkins) | 11/19/19 5:00 PM

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.

[Read the full article on* Physics Today *→](https://physicstoday.scitation.org/do/10.1063/PT.6.1.20190606a/full/)

[View full post](https://northerncal.swagelok.com/blog/the-mysterious-crystal-that-melts-at-two-different-temperatures)

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