[HN Gopher] Using saltpetre for cooling drinks (2013)
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Using saltpetre for cooling drinks (2013)
Author : d13
Score : 37 points
Date : 2022-08-27 08:27 UTC (1 days ago)
(HTM) web link (regencyredingote.wordpress.com)
(TXT) w3m dump (regencyredingote.wordpress.com)
| aaron695 wrote:
| teeray wrote:
| For those looking to skip the history lesson:
|
| > Saltpetre was most often used to cool wines during the Regency,
| by cooling the water in which the wine bottles were immersed. A
| large wooden tub, preferably of a cylindrical shape or, better
| still, wider at the top than at the bottom, was the ideal shape
| of a vessel to be used for cooling with saltpetre. This cooling
| tub should be lined with sheet lead or zinc and should also have
| a close fitting lid which would exclude as much of the warmer
| ambient air as possible. The thicker the surrounding wood, the
| better the cooling mixture would be insulated. A cooling tub with
| a capacity of ten to twelve gallons should be filled with four or
| five gallons of water. The cooler the water, the better, so water
| just pumped or drawn from a well would be most effective, since
| the water temperature would be about 75o Fahrenheit. Five to
| seven pounds of saltpetre should be pulverized to the finest
| powder possible. This finely-powdered saltpetre should be slowly
| sprinkled into the water and allowed to dissolve. Within about
| fifteen minutes the temperature of the water would drop twenty-
| five to thirty degrees, within a half hour the temperature would
| drop another four or five degrees. At that point, the temperature
| of the water would remain steady for over two hours, so long as
| the lid was kept on the tub as much as possible. After that, the
| water would begin to warm at a rate of about three or four
| degrees per hour, unless more powdered saltpetre was added to the
| water.
|
| And for the why it works:
|
| > Saltpetre cools water by producing an endothermic reaction.
| This is a chemical reaction whereby, as it dissolves, the
| saltpetre literally pulls the heat out of the water as part of
| that process, thus lowering the temperature of the water. For
| this reason, there is a limit to how cool the water can become.
| Once it has become fully saturated with saltpetre, the water is
| not able to absorb any more.
| jpollock wrote:
| Why is dissolving potassium nitrate in water an endothermic
| process ?
|
| https://socratic.org/questions/5422ba97581e2a47cb1a8acf
|
| "Dissolving potassium nitrate in water is an endothermic
| process because the hydration of the ions when the crystal
| dissolves does not provide as much energy as is needed to break
| up the lattice."
|
| Huh, which explains why it's reusable, dry it out, grind it up
| and you can use it again.
| [deleted]
| [deleted]
| diego_moita wrote:
| AFAIK, one type of saltpetre (potassium nitrate) was also widely
| used to preserve cured meats. Today we tend to use nitrites to
| avoid the spoiling of bacon, sausages, salami, speck, jamon and
| other cured meats. These became more used in late 19th century,
| known as Chilean saltpetre.
|
| The nitrites and nitrates is what gives cured meats their pink
| colour and are considered cancer inducing.
| jandrewrogers wrote:
| The instant cold packs commonly found in first-aid kits use a
| closely related chemical: ammonium nitrate. While technically a
| high explosive, it is effectively useless as such in the hands of
| the average person.
| thriftwy wrote:
| But somewhat useful as a fertilizer.
| beckingz wrote:
| Technically incorrect: ammonium nitrate on its own is not an
| explosive.
| blantonl wrote:
| Nowhere mentioned in this article, but wasn't saltpetre given to
| prisoners to reduce "sexual urges" within prisons? Or is this an
| old wives tale?
| [deleted]
| version_five wrote:
| I heard a similar urban legend about it being added to army
| rations. People said it was added (in the 90s) to cigarettes to
| prevent them from going out, and that smoking could make you
| impotent (which I never saw actual evidence of)
| mfincham wrote:
| This is a very long lived urban legend.
| ThrowawayTestr wrote:
| Kind of long winded but a nice article. I had no idea saltpeter
| was used for cooling.
| nibbleshifter wrote:
| I'd love to try this myself, but where I currently live - despite
| being an ingredient in a few traditional cured meat dishes -
| nitrate salts require a virtually unobtainable (to a private
| person) permit to obtain, because of terrorism concerns.
| masklinn wrote:
| FWIW the dissolution of table salt in water is also
| endothermic, though to a much lower extent than saltpeter: the
| enthalpy of solution for saltpeter is +34.9kJ/mol, for table
| salt it's +3.87.
|
| An other option is ammonium nitrate at +25.69, though you might
| also have trouble with terrorism regulations as it's both a
| common fertiliser and a component for explosives.
| nibbleshifter wrote:
| I often will use salt in ice baths specifically for that
| reason :)
|
| Ammonium nitrate used to be uses in the "instant ice/cold
| packs" for first aid, but has since been replaced with urea -
| I believe due to the terrorism regulations.
|
| Which means (as another poster suggested) I'll be trying urea
| as a way to chill drinks sometime soon I guess.
| jsjohnst wrote:
| > where I currently live
|
| Not surprised by your story, but still curious where you live?
| In the US, you can buy it in bulk quantity on Amazon. Mixing it
| with sugar was a ton of fun when I was a kid, smoke bombs that
| could totally white out a large backyard.
| nibbleshifter wrote:
| A Western European country.
|
| I could easily order it from overseas online, but the
| consequences are pretty harsh (violates the explosives laws).
| Not worth it tbh.
|
| Somewhere else I lived in Eastern Europe, it was available in
| shops in 100g bags for curing meat, etc, or at the garden
| shop in 25kg sacks as a fertiliser.
| UpstandingUser wrote:
| You can get it at the hardware store, it'll break down tree
| stumps pretty quickly (and very inexpensively).
| jsjohnst wrote:
| Yep, any place that has garden supplies generally has it.
| That's where I got it when I was a kid anyway, as that was
| years before Amazon's existence.
| PBnFlash wrote:
| Urea also is endothermic, and as it is used in diesel engines I
| am quite sure it's available globally.
| nibbleshifter wrote:
| Aye, urea is what's in the "instant ice packs" now.
|
| It used to be ammonium nitrate, but most brands switched it
| to urea a few years ago - presumably for reasons of "people
| could use the extremely nice, uncoated, very pure ammonium
| nitrate for nefarious purposes" (useful for explosives and
| methamphetamine manufacturing!)
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