Crystal with two different melting points

[Tom.G]

TL;DR

Back in 1896, acetaldehyde phenylhydrazone (APH) kept melting at two very different temperatures. A batch he produced on Monday might melt at 65 °C, while a batch on Thursday would melt at 100 °C. Here's why.

It turns out that the solid form is the same for the two situations but the liquid is two different isomers depending on external conditions during melting.

https://physicstoday.scitation.org/do/10.1063/PT.6.1.20190606a/full/

 

[DrClaude]

I'm not impressed. When I was a student, my entire class could synthesize the same molecule that would melt at different temperatures

Joking aside, this is a fascinating discovery. My favorite quote from the article:

Occasional forays to temperatures higher than the delicate equipment’s 100 °C limit led to “frowning technicians,” Meekes says, but the risk was worth it.

 

[Dr. Courtney]

Great article. Thanks for the link.

Highly recommended account of how data and sleuthing are supposed to work in science.