Wikipedia:Reference desk/Archives/Science/2025 June 19

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June 19

Boiling point of nitrogen

Do we have a table for the boiling point of diatomic nitrogen as a function of pressure, especially between atmospheric pressure and its critical point? The infobox at the start of our Nitrogen article says that the critical point is near 3400 kPa and 126 K, but there's no reference given for that. I don't see data for pressures lower than that, other than a boiling point of 77 K at some unspecified pressure presumably near atmospheric. Ideally I'd also like a table of the liquid densities as a function of temperature in this range. I tried to look for other articles on en.Wikipedia, or phase diagrams on Commons, but all I found are two phase diagrams for much higher pressures. I don't need high precision data. Nitrogen is sold in pressurized cylinders for cheap so I expected this data to be widely available. – b_jonas 11:30, 19 June 2025 (UTC)[reply]

doi:10.5075/epfl-thesis-4721 has a nice phase diagram on page 61. It's cited to doi:10.1088/0031-9120/7/4/010, whose full-text I cannot access at the moment, so I don't know if it simply copied the diagram, used experimental or theoretical values from it, or has some other cited underlying source of information. DMacks (talk) 17:24, 19 June 2025 (UTC)[reply]

The labels have been reset in a serif typeface, but the grid and curves, although redrawn, are virtually indistinguishable.  ​‑‑Lambiam 20:36, 19 June 2025 (UTC)[reply]

Oceani (sic) Foam? 1960s Soviet breakthrough.

(Science seems to be the best here but this is more materials science or consumer science.)

On an episode of Gaslit about Nixon and Martha Mitchell, John Dean's character drops about how the Soviets invented a cushion foam that "feels better than you imagine". [1] (youtube link ap isn't working)

Is this real? How do you spell it? Any other info on this, like why after the cold war no one makes it?

Thanks in advance! 2600:1700:6742:3C00:C8E3:FC65:9FD0:D2C3 (talk) 18:07, 19 June 2025 (UTC)[reply]

Just tried looking it up under several different spellings, and the only refs I found led right back to the show -- so I can safely conclude that this material is purely fictional. BTW, the entire story is highly implausible on several counts: (1) having personally lived in the Soviet block during the last few years of the cold war, I can confirm that their foam cushions were not actually all that good -- they were very saggy and tended to support you in exactly the wrong places; (2) Kennedy would never have risked using Soviet-made materials in Air Force One (of all places) regardless of their supposed quality, for risk of public scandal; (3) I have found confirmation that the cushions on Air Force One were in fact manufactured in the USA (oh, the good old days!); and (4) the properties attributed to this "Poshinaya foam" appear to be similar to those of memory foam, which was invented during that time period (just about the only historically accurate part of this whole thing), but by Nasa, not the Soviets! 2601:646:8082:BA0:D199:AB8A:25C3:B09B (talk) 00:23, 20 June 2025 (UTC)[reply]

Really appreciate your deep dive on this. Hollywood always makes it look real smh. Any other thoughts or comments are welcome but what you are stating makes sense in some ways. 2600:1700:6742:3C00:C8E3:FC65:9FD0:D2C3 (talk) 03:11, 20 June 2025 (UTC)[reply]

Now that I remember this, there were even calls by local health experts to avoid using foam cushions in home furniture (and especially in children's furniture) because they believed them (and probably with very good reason) to contribute to poor posture due to their sagginess -- which shows just how bad Soviet-block foam cushions really were! 2601:646:8082:BA0:D83C:8BF:CC86:2F61 (talk) 12:05, 20 June 2025 (UTC)[reply]

Can you tell me something about two headed snakes?

As far as I know, two headed snakes are relatively common compared to other Siamese twins. Is it true that the two heads often get angry with each other and disagree about where their body is going and start fighting each other? 146.200.107.90 (talk) 22:47, 19 June 2025 (UTC)[reply]

The following article from a reputable source might be of interest; however, I didn't read it because I was required to "Enter your email to read this article", which I'm unwilling to do:

• "Life Is Confusing For Two-Headed Snakes". Animals. National Geographic. 20 June 2025. --136.56.165.118 (talk) 00:42, 20 June 2025 (UTC)[reply]

Two quotes from that article:

"Just watching them feed, often fighting over which head will swallow the prey, shows that feeding takes a good deal of time, during which they would be highly vulnerable to predators," said Burghardt. "They also have a great deal of difficulty deciding which direction to go, and if they had to respond to an attack quickly they would just not be capable of it."

...

Snakes operate a good deal by smell, and if one head catches the scent of prey on the other's head, it will attack and try to swallow the second head.

There is no suggestion of anger being involved.  ​‑‑Lambiam 03:58, 20 June 2025 (UTC)[reply]

Unlike mammals, reptiles lay eggs, and the mother's body cannot detect and terminate severely deformed embryos early in development. Stanleykswong (talk) 20:18, 21 June 2025 (UTC)[reply]

Also, in placental mammals and many other viviparous animals, Siamese twins make delivery harder, endangering the mother. In humans it's almost certain to kill the mother without modern medical care. That increases the selection against genetic defects that cause Siamese twins. Some snakes employ some form of ovoviviparity. PiusImpavidus (talk) 09:03, 22 June 2025 (UTC)[reply]

Minor quibble: some species reptiles are viviparous (even some snakes). Two-headed snakes are probably rare enough that it would hard to look for a correlation with species. DMacks (talk) 12:01, 22 June 2025 (UTC)[reply]