Inject a diluted sample of gasoline into a gas chromatograph, and the trace shows at least 50 separate peaks. This guide explains how gas chromatography works as an instrument: a stream of inert carrier gas, a long, thin column inside an oven, and a detector at the far end that notices each compound as it comes out. Once you know what each part does, any GC trace becomes much easier to read. The four parts of a gas chromatograph David […]
Hit the round end of this glass teardrop with a hammer and it survives. Snap the thin tail with your fingers and the whole thing bursts into powder with a sharp pop. A Prince Rupert’s drop is nothing more than a blob of molten glass dropped into cold water, yet it puzzled 17th-century scientists for decades. Only in the last few decades has anyone measured what’s going on inside. The answer is a lesson in residual stress, the same physics […]
Slice into an onion and your eyes soon start to sting and water. Nothing in the whole onion is doing this. The irritant doesn’t exist until the knife goes in, and it’s made on the spot by a chain of chemistry that takes a fraction of a second. So why onions make you cry comes down to two enzymes, one unstable sulfur molecule and a discovery from 2002 that showed the textbook explanation was missing a step. Why onions make […]
Two liquids that mix completely can still be pulled apart by heat, because one evaporates more readily than the other. The choice in the teaching lab is usually simple vs fractional distillation: a straight path from flask to condenser, or the same setup with a column inserted in between. The column looks like a small addition, but it changes what the apparatus can do. Whether you need it comes down to how far apart the boiling points are. What distillation […]
The folk remedy behind searches for aspirin paste is a crushed aspirin tablet, moistened and held against a sore tooth or a bee sting. It sounds reasonable, since aspirin is a painkiller, so why not put it right where it hurts? The chemistry of aspirin and the published case reports tell a different story. This article is about that evidence. It is not a how-to and not medical advice. What aspirin is, chemically Aspirin is acetylsalicylic acid. PubChem gives its […]
Pour a little vinegar into a beaker, dip in a pH meter, and the reading lands well below 7, but nowhere near the pH of a strong acid at the same strength. The reason is that acetic acid gives up only a small share of its protons. Working out acetic acid pH comes down to one equilibrium constant, a bit of algebra, and knowing when the usual shortcut stops working. Why acetic acid is a weak acid In water, acetic […]