Wikipedia:Reference desk/Archives/Science/2016 December 4

= December 4 =

Erroneous Recycling
Many types of paper or plastic may appear recyclable to a non-specialist, but are actually technically or legally not recyclable in any given locality, e.g., pizza boxes, styrofoam, paper towels and napkins, granola/candy bar wrappers, etc. If someone deposits one of those items in the recycling can, what generally happens? Is there a huge contamination risk for the recycling facility? Assuming there are human sorters they might fish those items out, but perhaps not 100%... Bottom line -- how big of a problem is it if someone tries to recycle these "non-recyclable" items? --208.58.213.72 (talk) 05:34, 4 December 2016 (UTC)


 * I'm not sure, but I'd think the contamination would be relatively minor (unless this is really widespread), given the sheer volume of waste to be recycled. Also, regarding food scraps and such, they would probably tend to be chemically degraded during the paper recycling process (which uses harsh chemicals) and to burn up during plactics recycling (which involves high temperatures).  FWIW 2601:646:8E01:7E0B:F88D:DE34:7772:8E5B (talk) 08:54, 4 December 2016 (UTC)


 * I believe recycling centers typically pour items to be recycled out on a large conveyor belt, where people pick out items that can't be recycled, and separate the items that can be recycled into categories, perhaps also using devices such as magnets. StuRat (talk) 15:30, 4 December 2016 (UTC)


 * There numerous Internet sites where recyclable items are listed and discussed. For instance here. --AboutFace 22 (talk) 22:45, 4 December 2016 (UTC)
 * Thanks, all. However, the issue is not *which types* of items are recyclable, but what happens if someone (inadvertently or not) breaks the rules and non-recyclable items get into the recycling process inadvertently (if they are not spotted or removed by human or mechanical sorters). Thanks.--208.58.213.72 (talk) 03:11, 6 December 2016 (UTC)

Running crack
Is it possible, in principle, to dissolve cocaine in automotive gasoline, and then to recover it for street sale? Is a near-quantitative recovery possible, or would the process involve unacceptable losses? Would the recovered crack be fit for illicit consumption (note not for medical use), or would there be toxic impurities left which would make it completely unmarketable? 2601:646:8E01:7E0B:F88D:DE34:7772:8E5B (talk) 09:02, 4 December 2016 (UTC)
 * Wikipedia is not in the business of encouraging criminal activity. ←Baseball Bugs What's up, Doc? carrots→ 09:15, 4 December 2016 (UTC)
 * In case you didn't check out my second link, I'm asking this as a James Bond fan, not as a prospective drug runner! 2601:646:8E01:7E0B:F88D:DE34:7772:8E5B (talk) 11:15, 4 December 2016 (UTC)
 * Googling the subject briefly, here is an article that discusses the production of cocaine, which includes dissolving the stuff in gasoline or kerosene. So it sounds like it could work. ←Baseball Bugs What's up, Doc? carrots→ 12:00, 4 December 2016 (UTC)
 * All right, so Franz Sanchez can get his $500M worth of crack dissolved in four truckloads of gasoline -- but the question is, could he get it back again (in an alternative timeline where 007 doesn't get all of the stuff burned up along with Sanchez himself, of course)? Just from looking at the properties of cocaine, liquid-liquid extraction with an aqueous solution of e.g. hydrochloric acid might work -- but the question is, (1) would the losses be within acceptable limits (mainly a question of economics), and (2) would there be toxic chemicals from gasoline left in the drug to the point that it would be unfit for sale? 2601:646:8E01:7E0B:F88D:DE34:7772:8E5B (talk) 12:41, 4 December 2016 (UTC)
 * The reason "why" you are asking is not actually a valid defense against the rules of the ref desk, or Wikipedia for that matter. "Can you answer this question that sounds like medial advice, but I'm just curious"? for example. If it sounds like a duck and looks like a duck, the policy still applies. I am not in a position to do a policy search right now but it is against Wikipedia policy to detail how to perform illegal activities and detailed recipes for illicit substances. Having said that, I don't think this particular question crosses that line, simply asking IF it is possible is not really doing anything to encourage or enable it. Vespine (talk) 23:52, 4 December 2016 (UTC)
 * There is no such policy - indeed, I actually asked . Preserving ignorance is not our mandate, so when we don't know of any plan to commit a crime that would make us worry about conspiracy prosecution, there's no obstacle. Wnt (talk) 03:18, 5 December 2016 (UTC)
 * I'm sure I saw a policy about how much information should be included in our articles about nuclear weapons and recipes for high explosives. Vespine (talk) 03:45, 5 December 2016 (UTC)
 * Have you read our articles on nuclear weapons? They're pretty nice.  We really don't know how information will be used - odds are, the first person who goes looking through our archives to see if there can be coke in the gas tank will be a nark trying to crack a smuggling ring.  I feel bad about that, but not enough to stop talking about fun science. Wnt (talk) 03:55, 5 December 2016 (UTC)
 * Yes I have, they're among my fav articles, but they're very "high level", they don't go into details, I'm certain I read somewhere that this was not an accident. I'll see if I can dig it up, this certainly isn't really the place to be debating this. I thought there 'was' a general consensus that detailed recipes for things like high explosives would not be kept on Wikipedia, I might be wrong. Vespine (talk) 21:48, 5 December 2016 (UTC)
 * Wikipedia is not supposed to be censored for content. However, too much detail could run afoul of the axiom that Wikipedia is not a "how-to" source. As for making explosives, if the information has a valid source, then it's already public knowledge. ←Baseball Bugs What's up, Doc? carrots→ 21:53, 5 December 2016 (UTC)
 * It's not an "axiom", it's a style guideline for how to write an article (I assume you mean WP:NOTHOWTO). Which tells us not to write an article about chocolate chip cookies by saying to mix in the chips and set the oven to 375 degrees.  We're not addressing the reader as "you" and giving him commands; we should say "Chocolate chip cookies are typically made at 350 to 425 degrees[1][2][3]" and give him three recipes to look at instead!  The guideline doesn't say anything against telling people to do that on the Refdesk.
 * As for ethics, well, I come from a country that elected someone based on his promise to torture people, who called up the butcher of Davao to congratulate him for doing it "the right way", so pardon me if I have a decreasing patience for appeals to my ethics in general, let alone ethics implacably and openly opposed to the stated goal of "Imagine a world in which every single person on the planet is given free access to the sum of all human knowledge." which brought me to the project in the first place. Wnt (talk) 22:54, 5 December 2016 (UTC)
 * Our new president promised to torture terrorists, not people -- do you not know the difference, or do you not care?! 2601:646:8E01:7E0B:99F8:B355:9D57:7021 (talk) 02:07, 6 December 2016 (UTC)
 * Yes, that's the one. And, yes, more of a suggestion than an axiom. Ethics figure into it when someone tries to give professional advice, which no one here is qualified to do. As for Trump and his "mandate", Hillary got a lot more popular votes than Donald did, but he got the right states. I share your concerns about that, for sure. ←Baseball Bugs What's up, Doc? carrots→ 23:51, 5 December 2016 (UTC)


 * Gasoline by definition is made up of volatile hydrocarbons, so in theory anything dissolved in it can be dried out. Cross-border shipping can involve a markup of 100% or more, depending on the border, so it can make financial sense.  The interesting part of the question i.e. the part I don't know the answer to is whether cocaine in gasoline will cause trouble with the car.  It doesn't seem that different from gasoline components, I suppose -- with the exception of the nitrogen, which makes it an alkaloid.  Looking at  it appears nitrogen doesn't play that nicely with internal combustion engines.  Going through Customs sputtering a thick trail of smoke that drives all the drug hounds wild would not be a tactical move, though it might make for a great movie scene.  OTOH there are mechanics who can do marvellous, even miraculous things with an engine, and as I said, I actually have no idea. Wnt (talk) 03:10, 5 December 2016 (UTC)
 * Presumably it's in barrels, not in the gas tank. Otherwise you'd be burning away your profits as you drive. ←Baseball Bugs What's up, Doc? carrots→ 04:12, 5 December 2016 (UTC)
 * I was thinking more along the lines of a tanker truck, like in these videos. 2601:646:8E01:7E0B:99F8:B355:9D57:7021 (talk) 08:19, 5 December 2016 (UTC)


 * Clarification: note this section is appropriately titled - you can dissolve crack cocaine in gasoline, as it is a free base (uncharged), but powder cocaine (cocaine HCl) would not dissolve in an organic solvent (except, perhaps, with a phase transfer catalyst...).
 * And this may also be a way to recover it afterward -- simply reconvert it back to the chloride salt, and out of the gasoline it goes straight into the aqueous phase! 2601:646:8E01:7E0B:99F8:B355:9D57:7021 (talk) 02:11, 6 December 2016 (UTC)
 * This is a basic step in all cocaine preparation, which leads to substantial environmental damage as the gasoline, acid, and other materials are dumped into the environment.  That said, dissolving it in gasoline is therefore not a new or surprising insight from the point of view of the drug traffickers, and so presumably, not to the drug or customs agencies either. Wnt (talk) 13:24, 6 December 2016 (UTC)
 * I am not sure the local fauna's wellbeing is a drugmaker's highest priority. Tigraan Click here to contact me 15:09, 6 December 2016 (UTC)
 * Indeed, neither the flora either. Growing Coca plants usually involves destroying amazon rain-forest. But it has been suggested that perhaps environmentally-conscious celebrities (celebrities being a group which often abuse cocaine) be brought on board in publicly repudiating cocaine use explicitly on both environmental grounds referred to above ("I don't want to be responsible for destroying rain-forest and polluting the environment"), as well, as left at least 164,000 people murdered in Mexico alone, not even counting the death toll in other countries, involved in producing, transporting and delivering the stuff. As one expert said: We have "Blood diamonds", how about "Blood cocaine"? If a celebrity isn't concerned about their health, perhaps we can appeal to their social and environmental conscience? They do serve as role models to a significant degree. Admittedly, this would only work for powdered cocaine, not crack.  Eliyohub (talk) 13:51, 7 December 2016 (UTC)
 * The basic number as I recall is $100 billion yearly retail value per 20,000 killed; supposing a human contains 5 liters of blood and a drop of blood is a big 50 microliters, that's 100,000 drops of blood shed per person killed, and so 2 billion drops of blood total; thus Lady Macbeth might see a drop of blood in every $50 worth of cocaine snorted. The part where my perceptions would vary from the drug warrior's is that however bloody the demand for smuggled dope may be, the supply of it would seem less so - if an honest non-homicidal person synthesized cocaine in a lab in the U.S. to give to people he knew, every $50 worth he made would be a drop of blood less that would ever be shed.  And of course, with a complete end to Prohibition the deaths would cease altogether. Wnt (talk) 12:52, 8 December 2016 (UTC)
 * That drop of blood is a drop of human blood nevertheless. And across the globe, the drops add up to a river. I am not Macbeth. on the death toll per retail value please. And honest non-homicidal people seldom survive in the drug trade, at least once they move past the backyard-lab stage. It's kill or be killed, though some drug lords are significantly more sociopathic than others. Remember, if you get robbed of your stock at gunpoint, you can't exactly go to the police. So you need your own "security force". If you're lucky and well resourced, you can hire ex-commandos who tend to be more likely to handle situations with less violence (or are at least capable of doing so) and are well-disciplined. If not, you hire poorly-trained or untrained thugs with guns, who tend to be edgy and twitchy-fingered, nervous, and quick on the trigger. Los Zetas once mostly used commandos, who seldom struck the "wrong" target. As it lost these to arrests and crackdowns, it was forced to replace them with the thugs-with-guns variety, and the number of uninvolved law-abiding citizens killed went up. If your figures are correct, this simply shows the massive scale of the trade. And as to the "honest" bit, um, I think only internet porn sites have as bad a reputation for ripping off their customers as drug dealers do. And at least the internet porn consumer, if he was smart enough to pay by credit card, can often recoup their cash. The drug trader's equivalent of claiming a refund for a dodgy deal usually involves significant violence. Eliyohub (talk) 14:45, 8 December 2016 (UTC)

Reflection of light when momentum is transferred
I'm aware of the law that the angle of incidence equals the angle of reflection. However, since some momentum is transferred when light hits a mirror, I was wondering, is this quite true? Of course, in common experience the momentum transferred to the mirror by light is undetectable, but it is there, and if there is some transfer of momentum to the mirror in a direction perpendicular to the normal of the mirror, the angle of reflection should be subtly different to the angle of incidence.--Leon (talk) 10:15, 4 December 2016 (UTC)
 * Yes, the angle will change - this is a fairly simple treatment of the problem. For an initially stationary (ν = 0) but low-mass mirror, we can drop the second term (rather than the third) in Equation 6 - derivation of the rest of the calculations is left as an exercise for the reader.  Tevildo (talk) 20:26, 4 December 2016 (UTC)


 * Whether the angle changes depends on your choice of reference frame. Assuming an instantaneous pulse and a perfectly elastic collision (as Tevildo's source does), wrt the most symmetric frame, the incident and reflected angles are the same. (Also, the frame-independent spacetime angles are the same.) With respect to any other frame, the angles are given by the aberration formula, and will be different in general. The most symmetric frame is the one where the mirror is moving at the same speed in opposite directions before and after the collision.
 * The derivation in Tevildo's source is more complicated than necessary because it doesn't use the symmetric frame. (The author is aware of that, though, and links some earlier articles that presumably do use an easier derivation.) -- BenRG (talk) 23:51, 5 December 2016 (UTC)

no information on the bond energies of a pi bond (ALONE), separate from the C=C sigma bond?
Why doesn't our article comment on the bond energies of the C=C pi bond (separate from the sigma bond)? I only ask this because I am drafting tutoring notes and I want to give my students a ballpark figure. Am I correct to guess that a pi bond in say ethylene is around 50 kcal/mol? Yanping Nora Soong (talk) 18:00, 4 December 2016 (UTC)
 * This article in J. Chem Ed looks promising. -- Jayron 32 14:15, 5 December 2016 (UTC)
 * You could use diatomic C2 (:C=C: with ground state $1$&Sigma;$+ g$) to gauge this, since if you draw the MO diagram you'll find that &sigma; and &sigma;* are both fully occupied and the net bond order of two comes only from the &pi; bonds. But do note that strange cases like this are not representative because the presence of a &sigma; bond prevents the &pi; bond from having its optimal bond length, which tends to "want" to be shorter than that of the &sigma; bond between the same two atoms: see this article. The cohesive energy of gaseous C2 is 609 kJ/mol (two &pi; bonds), not far from that of a "normal" C=C bond at 614 kJ/mol (one &sigma; and one &pi; bond) according to Wikipedia. Double sharp (talk) 15:01, 5 December 2016 (UTC)
 * There is a paragraph in pi bond that begins "Pi bonds are usually weaker than sigma bonds." It includes an orbital-overlap explanation but not a quantitative comparison. Later in that article is additional content about the difference of alkane vs alkene (the "ene" detail adding less strength than was present with just the "ane"), and the confounding ideas of differing preferred length/etc that Double sharp notes. The JChemEd article Jayron notes seems at a quick glance to base some pi-strength calculations on cis/trans isomerization kinetics, which relies on the well-disputed idea that such a process involves breaking the pi bond (with the two atoms retaining sp2 nature but rotating their respective planes compared to each other)--see . I think our pi bond article needs updating for that! DMacks (talk) 00:44, 6 December 2016 (UTC)

What large cheap vessel to use for a chloroform vapour bath?
I would like to use a chloroform vapour bath to smooth some tall parts that I intend to 3D print. The pieces will be 33 cm tall. I can get a PP bucket and lid at a resonable price but the Cole Palmer website says PP will perform adequately although it will be attacked while two other websites suggest it will be unacceptable. Could the bucket be coated with anything cheap? I want to use this container many times and although the container won't be full of liquid chloroform there will be paper towels lining the walls soaked with chloroform. Thanks for any suggestions. Seans Potato Business 18:14, 4 December 2016 (UTC)


 * I'm naturally lazy, so I would first try lining it with some cheap Jumbo Size Turkey Roasting Bags being nylon they should be resistant to chloroform and more than large enough to contain said object. But why consider just a bucket. The local scrap yard may have many a 5 gallon drum or other metal container where chloroform attack is not going to be a problem. P.S. Doing this in a well ventilated area means doing it outside in the open air. Not only is the vapor  explosive but it can bring on cardiac arrest.--Aspro (talk) 19:28, 4 December 2016 (UTC)


 * While there are obvious health hazards associated with chloroform use (likely carcinogen, and if you can smell the vapor you're likely over the airborne concentration permitted in the workplace), chloroform – as liquid or vapor – is not flammable or explosive. If you expose it to flame or high heat, it can produce some nasty decomposition products, though.  Please be sure you're familiar with all the hazards associated with this chemical (and also the appropriate, safe, legal methods for disposal of chlorinated solvents) before using chloroform.
 * Most important, please don't trust random individuals on the Ref Desk to provide you with safety training or advice; unfortunately, there are a few regulars here who give very confident and assertive advice without actually knowing what they're talking about. Start with the appropriate safety data sheet (several are linked from Chloroform (data page)).  TenOfAllTrades(talk) 19:53, 4 December 2016 (UTC)


 * TenOfAllTrades as always give good advice not to take what we say here as gospel and to seek qualified  advice. His own utterance give proof to this when he sates as liquid or vapor – is not flammable or explosive. Using analytical   quality   chloroform perhaps, according to the data sheets he quotes. But we don't know the grade/quality nor contaminates in the OP's  work place which can cause a   chloroform fuelled explosion, so one should always consider it to be potentially explosive. “However, the addition of small amounts, of any flammable compound or an increase in oxygen content will make chloroform flammable.” So now the OP has some advice from just not any old  editor to do it out in the open unless he a has qualified staff and a fully equipped lab, and obviously, should he have such a lab, equipped with a fume cupboard, he would'nt need to be asking this question here.--Aspro (talk) 20:49, 4 December 2016 (UTC)


 * It ought to go without saying that stuff to which you've added other, different stuff isn't quite the same stuff as stuff without the other added stuff. It's certainly true that someone unaware of that principle shouldn't go near chemistry...or the kitchen.  TenOfAllTrades(talk) 01:07, 5 December 2016 (UTC)


 * I tried "chloroform vapor bath" and "chloroform vapour bath" through Google and found a total of four hits - one here - two of which say in the snippet it's 61 degrees C. So I have to ask... where is the original source or reference for this idea?  Maybe you have some other process in mind, like chloroform vapor polishing, which turns up just a few hits; there are apparently a lot of other kinds of vapor polishing.  The most familiar meeting of chloroform and polypropylene to me is in the Eppendorf tube, a kind of centrifuge tube.  See  - the polymer will definitely resist, but the plasticizer of this anonymous bucket may not be built according to Eppendorf's standard for tubes they know people will do their plasmid minipreps in.  There are apparently some issues with certain metals like magnesium and aluminum also though.  Wnt (talk) 03:39, 5 December 2016 (UTC)