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Last night I left a bottle of cleanser in my car, and during the 5-degree night the cleanser turned to a sludge.

This started me thinking.

Lots of people living before the development of the thermometer probably noticed that on cold nights some liquids freeze but not others, and that liquids can be put in order by freezing point such that all of those liquids to the left of some point on the spectrum will freeze while all of those to the right remain liquid. I imagine fresh water, sea water, medicines, juices and alcoholic drinks might have been interesting examples, of which many people had plenty of experience.

Do we have written record of this train of thought in the ancient world?

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Not really. Using multiple liquids to register a single temperature probably would have been impractical, but crude thermometers appear already in antiquity. Philo of Byzantium c. 240 BC used a tube from a hollow sphere to a jug of water. When the sphere was in the sun bubbles were released as air expanded out of the sphere, when moved to the shade, the water rose in the tube as air in the sphere contracted. Heron c.50 AD described similar devices in Pneumatica, and it is known that such pioneers of modern thermometers as Galileo and Fludd read Heron.

Galen c. 170 AD came even closer. He took boiling water as the top and melting ice as the bottom of the scale, with their mixture in equal parts as the neutral point. He then inserted four degrees above and below the neutral point by using the corresponding mixtures, thus making a nine-point scale, see Thermometer on Hmolpedia.

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    $\begingroup$ Why would multiple liquids to register a single temperature be impractical? $\endgroup$
    – Chaim
    Commented Jan 31, 2019 at 19:55
  • $\begingroup$ @Chaim Devices with fewer elements are easier to make, and it is unclear how to compare intervals between freezing points of different liquids. $\endgroup$
    – Conifold
    Commented Jan 31, 2019 at 20:08
  • $\begingroup$ I guess two things are happening. First, I'm asking about the historical record, and you're saying that there's no record of such an event. I understand that. $\endgroup$
    – Chaim
    Commented Jan 31, 2019 at 22:27
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    $\begingroup$ But second, we seem to be discussing the practicality of the event. People must have noticed that sometimes the water freezes but not the wine, and sometimes both freeze but not the vodka, and seen an indication of how cold the night. Are you doubting that, or just observing that this would not be a very precise way to measure temperature and would not lend itself to any definition of the degree? The insight might have suggested, or serendipity might have provided, otherwise identical bottles holding these liquids, which would have been a step in the right direction, I think. $\endgroup$
    – Chaim
    Commented Jan 31, 2019 at 22:27

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