mindstalk: (science)
Followup to my last post:

Here's a table of fat and oil melting points.

Selecting and sorting by temperature, in Celsius:
Lard 41
Palm oil 35
Cocoa butter 34
Gallium [do not eat] 30
Coconut oil 25

Peanut oil 3
Water 0
Olive oil -6
Rapeseed (canola) oil -10
Soybean -16
Sunflower -17
Linseed -24

As you can see, at the extremes there are gaps of 6-7 K. Sometimes less. But there's a 22 K gap between peanut and coconut oils. Take out coconut and gallium, and it's a 31 K gap.

As I said last time, in a way it makes sense: coconut oil was surprising because I hadn't encountered anything before that melts at practically room temperature. But still, wow. Wonder if there's a selective pressure: animals wanting fats that stay solid even under heat, plants wanting oils that stay liquid even freezing cold, no one wants a transition at 20 C. As for non-biological substances... I guess one rarely needs a household substance that would change phases at such temperatures, too.
mindstalk: (science)
So, earlier this summer I bought a jar of coconut oil from Trade Joe's. It was nice and solid.

A while after bringing it home, I noticed it had gone completely liquid. "Huh."

Turns out the melting point is a shade under 25 C. And yeah, in recent months my kitchen was typically warmer than that. Not anymore though, and it's gone solid again.

But that got me wondering about a crude thermometer, or calibration set for normal ones, made out of various substances with different melting points. Especially if household substances. "That's solid, that's liquid, must be between 25 and 30."

Doesn't seem likely though, at least not without bugging a chemist for obscure compounds. I found a table of oil and fat melting points. Butter is around 35, ghee a bit higher, tallow high 30s or 40s. Vegetable oils are mostly negative, with peanut oil sneaking in at 3 C. Chocolate is said to be about 30, though that seems low for outright melting IME. The highly non edible gallium is also 30.

But stuff between 3 and 30? Well, there's coconut oil... otherwise, something of a desert, which makes sense: the coconut oil was so surprising precisely because one doesn't encounter things melting at room temperature.

Honey is said to liquefy more rapidly under 10 C, but I'm not sure how long that takes, and it's not spontaneously reversible.

Woo hoo, extra-appropriate icon for this post!

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