Debye–Hückel
Two anomalies swim in a world difficult to define.
Debye–Hückel theory concerns non-ideal electrolyte solutions. Containing ions, they are pretty hard to describe mathematically. Personally I wouldn’t try to attempt it, and apparently no one else wants to either since you can legally just throw an activity coefficient at the solution and call it a day.
NOTE: This is one picture you need to back up from a bit so that the lineart comes into focus correctly.
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Alternate: a bit more yellow, like a sea of Gatorade… mmm gotta get those non-ideal electrolytes
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And just to have a more spectral version:
