Wikipedia:Reference desk/Archives/Science/2023 May 21

= May 21 =

Can moth wings heal?
If the wing of a moth is injured inadvertently by a human trying to picking it up gently to catch and release, can the wing heal?136.36.123.146 (talk) 03:59, 21 May 2023 (UTC)
 * There are researchers at The Lepidopterists' Society who may be contacted about the question. On this website Judith Willson writes: "Insect wings don’t grow back or heal, and a moth with a broken wing is never going to recover. If the moth is otherwise uninjured, you can look after it though. All the moth needs is somewhere quiet and safe, something to eat and something to rest on. Moths don’t live very long anyway, but you can provide it with a nice life for the time it does have left." Philvoids (talk) 12:52, 21 May 2023 (UTC)
 * I saw a video not that long ago of a butterfly's wing being repaired with a prosthesis by microsurgery. --Lambiam 09:56, 22 May 2023 (UTC)
 * It can be done with a piece of tape. Abductive  (reasoning) 15:48, 24 May 2023 (UTC)
 * If you need to move a moth, let it crawl onto you (or an object that you hold) rather than trying to pick it up. --User:Khajidha (talk) (contributions) 14:24, 21 May 2023 (UTC)

Expert help needed for Downs cell
It seems that the originally correct article on the Downs cell has been corrupted from claiming that sodium is produced to that magnesium is produced. When web-searching for Downs cell I cannot find anything that supports this statement, but I'm not a chemist, so this needs to be resolved by a chemist. Rursus dixit. ( m bork3 !) 16:37, 21 May 2023 (UTC)
 * Use of the Down's cell in electrolysis of molten sodium chloride to produce sodium metal and chlorine gas is attested here. Processes for electrolytic production of magnesium are documented, but none of these involve Down's cells (magnesium is mainly produced in China via the energy-intensive pyrometallurgical Pidgeon process). A one day effort on 29.11.2019 by User 118.137.73.73 to edit sodium out and magnesium in as a "factual error....fixed (thanks to me)" seems entirely mistaken and I agree with Rursus that those edits should all be reverted. Philvoids (talk) 17:36, 21 May 2023 (UTC)
 * Certainly looks to me like you are entirely correct, congratulations on spotting that. NadVolum (talk) 20:43, 21 May 2023 (UTC)

Recycling of gunpowder
For the purposes of a fictional historical narrative I have in mind —

Suppose a small pacifist European nation in the later 17th century were to come into possession of a very large quantity of gunpowder (they've just defeated an attempted invasion and captured all the enemy's armaments), how could they best dispose of it usefully, given that: (Yes, I have read Gunpowder, and to anticipate a sidetrack, they can re-use the metals, wood, etc. of the captured armaments for domestic purposes.)
 * they don't need it for armaments themselves (they have effective other means – don't ask);
 * they don't want to sell it to other nations (who might use it in warfare);
 * they use little or none for construction and quarrying;
 * they already have enough for fireworks, etc.

My initial thought was – would it be any use as fertiliser? {The poster formerly known as 87.81.230.195} 90.199.210.77 (talk) 17:31, 21 May 2023 (UTC)


 * If there is an economic way to turn the sulfur into a salt such as calcium sulfate, the mixture would become much less explosive and, I expect, a good fertilizer. --Lambiam 18:01, 21 May 2023 (UTC)
 * Repeated soaking and filtering would remove the KNO3 which could be used as a fertiliser. The residue would be a sulphur/charcoal mix which is non-explosive. Martin of Sheffield (talk) 19:02, 21 May 2023 (UTC)
 * Thanks for the responses (so far). I should perhaps have emphasised that only a 17th-century knowledge base is available to them: I was wondering if just sprinkling the gunpowder lightly on tilled fields or pasture would be viable. I doubt if explosiveness would be a factor after the first rain shower. {The poster formerly known as 87.81.230.195} 90.199.210.77 (talk) 21:12, 21 May 2023 (UTC)
 * Some online sources state this will work just fine, but these are not reliable sources in the Wikipedia sense. Thinly sprinkled gunpowder is probably not dangerously explosive anyway. --Lambiam 09:47, 22 May 2023 (UTC)
 * Spreading sulfur will make the soil more acidic, so dissolving out the KNO3 in water and using this as fertilizer would avoid acidification. Graeme Bartlett (talk) 09:57, 22 May 2023 (UTC)
 * As stated above, saltpetre can be extracted from the mixture using water and can then be used as fertiliser. The remaining mixture of carbon and sulphur is harder to separate. It can be done by extraction with a non-polar solvent (carbon disulphide is suggested, but wasn't known yet) or by melting sulphur at 115°C, then filtering. It may be tricky to do. Or you can simply burn the C-S mixture, creating SO2 and CO2. Blow the smoke through a mixture of water and limestone (calcium carbonate) and you get wet calcium sulphite, which gets further oxidised to calcium sulfate. On sulphur-poor soils, it may be useful as fertiliser, but it's more commonly used as building material: plaster of Paris. This process is related to flue-gas desulphurisation and was invented around 1850, but doesn't require a huge suspension of disbelieve to do before that time. Directly throwing the gunpowder on the fields may work as a fertiliser, but the sulphur may do more harm than good. PiusImpavidus (talk) 10:43, 22 May 2023 (UTC)
 * Further thanks. So, if the main problem of using raw gunpowder as fertilizer cum soil treatment (I imagine it would also have an effect on soil textures and aeration) is acidification, might it be practical (and within the scope of late 17th-century know-how) to mix in a cheaply available alkaline material, such as crushed limestone? My fictional protagonists are not desperate to use the surplus tons of gunpowder at all costs; they just want to 'de-militarize' it cheaply – if they can't find an easy useful application, they might just dump it in the Baltic. (Yes, that might have deleterious ramifications, but they wouldn't know that. {The poster formerly known as 87.81.230.195} 90.199.210.77 (talk) 12:33, 22 May 2023 (UTC)
 * Once the potassium nitrate has been removed as already suggested, the remaining sulfur/charcoal mixture (when dry) would be a perfectly good dusting powder to use as a fungicide or pesticide, in particular for grapes. I assume that any self-respecting small European country would have a thriving wine industry.... Mike Turnbull (talk) 13:15, 22 May 2023 (UTC)
 * Not along the Baltic coast: too cold for grapes, especially in the Little Ice Age. But maybe those people like cider too. PiusImpavidus (talk) 13:54, 22 May 2023 (UTC)
 * Elemental sulfur is acidic because it hydrolyzes and forms sulfuric acid. Sulfuric acid reacts with limestone in the reaction
 * CaCO3 (s) + H2SO4 (aq) CaSO4 (s) + CO2 (g) + H2O (l),
 * producing effectively gypsum. --Lambiam 05:34, 23 May 2023 (UTC)
 * Which is used as a fertilizer! Thanks Lambiam, and the other responders. I'll have my 17th-century Baltics mix the surplus gunpowder with crushed limestone and sprinkle it on some fields. Close enough for fan-fiction. {The poster formerly known as 87.81.230.195} 90.199.210.77 (talk) 14:26, 23 May 2023 (UTC)
 * Sulphur is used as a soil improver. Potatoes in particular benefit from a dose. DuncanHill (talk) 14:32, 23 May 2023 (UTC)
 * Not in elemental form, I suppose, but in bioavailable form as a component of a sulphate. --Lambiam 14:08, 24 May 2023 (UTC)