> Its peculiar behaviour, such as its surprising stability despite being highly unsaturated, hinted at a deeper mystery that would not be fully resolved until the mid-19th century with the proposal of its cyclic structure.
How were chemists in the early 19th century able to determine benzene must be highly unsaturated without knowing its structure? Did they simply combust it and measure the amount of water vapor and carbon dioxide produced?
There's a two step-process to stochiometry.
The first step, as people have elaborated below, is combust the compound and measure the weights of various oxides, which (after the atomic masses of the relevant elements were settled around the 1820s) lets you work out the empirical formula of an unknown molecule. For benzene, this would tell you that there is 1 C : 1 H, but this doesn't tell you if it's C₄H₄ or C₆H₆ or C₁₁₁H₁₁₁.
The second step is to determine the molar mass of your compound, which requires finding something that depends on the amount of substance but not the mass directly. (In modern times, this is primarily mass spec). Back in the 19th century, this is probably abusing the ideal gas law, which lets you compute the number of moles in a gas given the pressure, temperature, and volume of a vessel. Combine this with the mass of that container, and you know how much a mole weighs. If you get out, say, 77g/mol, and you know that the ratio is 1 C : 1 H, well, the only formula that makes sense is C₆H₆ (which should ideally have 78g/mol, but you might not get the right answer for various experimental reasons).
What these early chemists accomplished with, to our eyes, extremely crude methods is astounding. Physical methods like weighing, burning and collecting residue; describing crystallization and precipitation behavior, even smelling (and sometimes tasting) was at one point a routine thing to do.
The story of how Oxygen was discovered was super interesting and involved all of these methods.
Argon is an interesting one. A comparison between chemically synthesised nitrogen and ‘pure’ nitrogen extracted from the air (with the oxygen, carbon dioxide and water removed) revealed a discrepancy:
https://en.wikipedia.org/wiki/Argon#History
https://www.youtube.com/watch?v=loqudG71uBM (Chemistorian, noble gases)
Wow. Pre that discovery what did they think explained phonomenon like snuffing out a candle. Or blowing air on a fire.
https://en.wikipedia.org/wiki/Phlogiston_theory
I think you're right,
https://en.wikipedia.org/wiki/Kaliapparat
Yeah an apparatus like that and work out that benzene had a very different carbon dioxide to water ratio than something like hexane.
How cool, it's still in the ACS logo! Germans have the best names lol. Calibration apparatus.
> "Calibration apparatus"
I believe it's kali from German Kaliumhydroxid[0] (KOH, what it uses to dissolve CO2), from the same "potassium" root as al-kali in English, from medieval Arabic[1]. (And also metonymically a name for the coastal salt-marsh plant[2] from which medieval workers sourced potash/potassium[3]. I actually submitted that plant to HN [4] a few days ago, but no one was excited about it. They were once an essential ingredient in glassmaking, hence their other name, "glasswort").
[0] https://de.wikipedia.org/wiki/Kaliumhydroxid
[1] https://en.wiktionary.org/wiki/kali#English
[2] https://en.wikipedia.org/wiki/Salsola_kali
[3] https://en.wikipedia.org/wiki/Potash#History
[4] https://news.ycombinator.com/item?id=44128748
The literal meaning is indeed potassium apparatus / device / contraption. The Kali part is indeed shortened from Kaliumhydroxid.
Strangely enough, the modern German name is Fünf-Kugel-Apparat, "five balls apparatus". I found that one simply by going through "Other languages" on Wikipedia.
And benzene is called Benzol in German. And gasoline is called Benzin - that word has false friend potential because it seems more similar to benzene. It is also not derived from the name of Carl Benz of Mercedes-Benz fame who used it in the first practical automobile that he invented.
No, it's from al kali ne.
Yes.