Wikipedia:Reference desk/Archives/Science/2019 December 19

= December 19 =

Ion exchange membranes and electrochemical compressors
Can gases like nitrogen and/or chlorine be compressed by using anion exchange membranes in electrochemical gas compressors? Thanks!--109.166.131.155 (talk) 11:29, 19 December 2019 (UTC)
 * Cool idea. Not my area of expertise but, I found a 2017 paper which shows it can be used for compressing ammonia. It says that it has previously only been used for hydrogen. They also seem to have a newer paper showing that it works with CO2 too. I don't know why it wouldn't work with N2 or Cl2 in principle. Pelirojopajaro (talk) 15:57, 19 December 2019 (UTC)
 * N2 may be easier than Cl2; Cl2 is much more reactive with a broader range of substances and I would be concerned about such unintended side reactions. N2 is basically inert though.  -- Jayron 32 17:36, 19 December 2019 (UTC)

Water, water everywhere...
Nor any drop to drink. How do salt-water aquatic animals acquire "fresh" water (essential for all life as we know it). Is it somehow absorbed through the skin, leaving salt behind? Is salt water consumed and the salt somehow excreted? Or, ... (?)  Is the mechanism different for fish (eg: sharks) as opposed to mammals (eg: whales)? 107.15.157.44 (talk) 21:55, 19 December 2019 (UTC)


 * See Surviving in Salt Water from the American Museum of Natural History. Alansplodge (talk) 22:36, 19 December 2019 (UTC)
 * And How can sea mammals drink saltwater? which answers the question for manatees, seals and sea lions, but "For most whales and dolphins, however, we simply do not know how they get their water, because it is difficult to observe these animals". Alansplodge (talk) 22:39, 19 December 2019 (UTC)
 * For more detail on mammals, see Osmoregulation in Marine Mammals. Alansplodge (talk) 22:49, 19 December 2019 (UTC)
 * Thanks, Alansplodge (am reading).  From the 1st link: "A gland in the shark's digestive system gets rid of excess salt".   I cannot find that gland's name or any mention in the Shark article.   107.15.157.44 (talk) 23:31, 19 December 2019 (UTC) -- P.s.   found it here:
 * The shark article says they don't need one:Shark
 * basically, it says that sharks are salty Rmvandijk (talk) 10:44, 20 December 2019 (UTC)
 * Shark article may be wrong (perish the thought): "A special gland near the end of the intestine, called the rectal gland, absorbs extra salt from the blood and passes it into the intestine to be excreted. These two adaptations function together to ensure that sharks do not dehydrate". From Sharks - Water And Salt Balance. More reliable sources are:
 * THE SHARK RECTAL GLAND MODEL: A CHAMPION OF RECEPTOR MEDIATED CHLORIDE SECRETION THROUGH CFTR and
 * Mechanism of active chloride secretion by shark rectal gland: and
 * Function of the rectal gland in the spiny dogfish (a dogfish, is a small type of shark), also
 * The rectal gland of Squalus acanthias: A model for the transport of chloride.
 * Alansplodge (talk) 15:18, 20 December 2019 (UTC)


 * Plenty of animals, notably a number of herps, manage with salt or brackish water by drinking it, then having some additional mechanism or "salt gland" to excrete the excess salt. Even some seabirds do this. The gland is usually either a modified tear duct or gland in the nose. They can appear to "cry" tears of brine, or even to sneeze out salt crystals. Most such animals also have kidneys which can tolerate a high salt diet and help by losing less water during urination, and they may be able to recover more water through their bladder walls (reptile urine is practically solid). This may be a re-use of an adaption for desert life, then enabling life in a wet but salty environment. Andy Dingley (talk) 00:22, 20 December 2019 (UTC)
 * There's a nice video of marine iguanas doing just that at . Bazza (talk) 11:09, 20 December 2019 (UTC)