In an experiment that Gregory J. Rummo teaches his general chemistry students, the students make six solutions of known concentrations of Fe(NCS)2+, aka isothiocyanatoiron (III), in dilute nitric acid. Students then measure how much light at 447 nm that each solution absorbs to understand the reaction between the iron and the thiocyanate.
But on this particular day, this set of samples was at just the right angle to catch the light so that the normally red-orange solutions looked like gold.
Credit: Gregory J. Rummo, @GregRummo on Twitter
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