Wikipedia:Reference desk/Archives/Science/2014 December 6

= December 6 =

How to make crystal meth ?
No, I don't need step by step instructions. I'm just wondering if it's as difficult as portrayed in the series Breaking Bad, where apparently only one person can make it properly. Somehow I doubt it. StuRat (talk) 01:27, 6 December 2014 (UTC)
 * History and culture of substituted amphetamines. -- ToE 01:41, 6 December 2014 (UTC)
 * Even that series didn't really portray it as hard to make; the premise was that the chemistry teacher could make it with extreme purity. Which is a little silly since the process of purifying the product is fairly separate from the synthesis, though I imagine separating a racemic mixture of d- and -l methamphetamine might be troublesome and wasteful if one of the older synthesis routes is used.  Also silly in that I doubt meth users really can assess 95% vs 99% purity with any great accuracy.  OTOH the suggestion that impurities have some harmful effect tends to come up often in discussions of why giving amphetamine to kids is therapeutic when done by a doctor but not by a drug dealer ... but I've never seen evidence to back up the claim (would certainly be interesting).  More impressive would be chemists making the product from scratch without using any DEA listed precursors, but that isn't the plot of the movie - from a quick glance at the Breaking Bad article I see they used the phenylacetone method (which produces racemic product) to avoid limitations of pseudoephedrine supply, but that still isn't particularly safe in today's America because even phenylacetone is scheduled now.  (Hell, even Ma Huang is banned, supposedly as a matter of herbal safety, and I don't know if anybody ever really used the plant for making meth) Wnt (talk) 05:16, 6 December 2014 (UTC)
 * Edit: Just wanted to mention it should be assumed that my posts as I'm guessing with others here will include spoilers up to the end of the series. IIRC the phenlyacetone was supposedly produced in a tube furnace. The bigger problem in the show was acquiring methylamine. When it wasn't supplied by Gustavo Fring, they resorted to stealing it first in a barrel, later from a freight train Nil Einne (talk) 13:48, 6 December 2014 (UTC)
 * BTW, I found two sources which refer to interesting points      . The method depicted in the show produces a racemic mixture. Walter White's method is supposed to produce not only a 99% pure, but 99% chirally pure drug which makes sense since the stuff is supposedly super potent, which is unlikely if you're having a racemic mixture. It's suggested in the series that Walter White has a method of separating the enantiomers. Some of the linked sources express scepticism it would be possible on the scale and specificity claimed in the show. Or if it was, Walter could just (patent I guess) and sell this method and get probably far richer than he ever got on the show (although perhaps this wouldn't fulfill what he's trying to get out of his work, it's strongly implied by the end of the series the money was really only a minor thing). Others suggest it might be possible at least for methamphetamine, although a number of these also suggested it didn't make much sense. A skilled chemist would likely use a method to selective produce (or even specifically produce) the desired enantiomer, reducing waste and making isolation easier, and that even with the legal restrictions there's likely no reason Walter couldn't have done so. Edit:In other words, even though it may be possible, there's no apparent reason to do it that way, and clear reasons not to. Another interesting point and one reason I'm reply to my reply, many sources agree that stealing methylamine makes little sense, a skilled chemist could produce it fairly easily from more readily available ingredients. Probably easier than producing phenylacetone in a tube furnace (e.g.  and I think some of the earlier links), although that may have been a reference to Uncle Fester (author)  . OTOH, the stealing was obviously a desired plot point and I guess the producing phenlyacetone using a difficult method emphasised the "Walter White is super" plot point. (Although I can't help wondering if producing phenlyacetone using a tube furnace is more in vein with producing a racemic mixture, suggests the chemist either doesn't know what they're doing or is more about flash than substance since there's no reason to do so.) Nil Einne (talk) 06:03, 7 December 2014 (UTC)
 * I am not a watcher of the show, but have seen a few seasons, my understanding was what made it difficult was both the quantity and the quality, Walt was making high-grade meth on a large scale - homebrew methods for small time sells and low grade quality, would be much easier, I am sure. You may want to read the following, especially, ; relating to the facts of the show about meth and their relation to reality:, , . This is just a fact sheet, but mentions that normal street purity is lower than the 99% claimed in BB (this isn't the best source, I'm sure better DEA sources, etc. could be found) . Here' a forum post about evaluating meth purity by assessment, , that may be of interest. These, , , , , talk about, and how to, make meth. This , discusses the "shake and bake" method of making meth and dangers associated. Finally, these may be of interest: , , . As with anything, understanding and perfecting -vs- producing a single thing are very different: for an analogy, it may be difficult to discover and exploit exploits in computer security directly, but almost anyone can run a program written by someone else. Meth isn't that different, anyone can follow instructions, especially, to make a single thing a single way if they have the ingredients; but to do it safely, consistently, at a high-quality, and be able to scale it, that is going to take someone more talented. (excuse stupid grammar mistakes, I did not have a chance to proofread and have to run).Phoenixia1177 (talk) 05:18, 6 December 2014 (UTC)


 * There's a HUGE difference, of 400%, between an impurity of 99 and 95%. Is this in need of further explanation? μηδείς (talk) 00:53, 7 December 2014 (UTC)
 * Apparently it is (in need of further explanation). Wnt was comparing purities of 95% and 99%, not impurities.  I wouldn't care if the cane sugar I add to my coffee was 95% or 99% pure as long as the balance was dextrose.  If the impurity is strychnine, however, I'd want a lot more nines.  Ivory soap may be "99 and 44/100% pure", but I've always figured that the important question concerned the makeup of that other 0.56%. -- ToE 16:59, 7 December 2014 (UTC)


 * Forgive the extra im-, but the song remains the same. I don't know what impurities might be found in meth, but there a lots of chemicals where a 5 times larger dose is a lethal one. μηδείς (talk) 18:29, 7 December 2014 (UTC)


 * But presumably those impurities aren't immediately fatal, even at the higher level, or we would have millions of meth users dropping dead immediately. Many of them die, but more from chronic user side-effects (like sleeping out in the cold, not eating, and trying to rob a casino to get meth money with nothing but a sharpened screwdriver).  Some "impurities" might even be beneficial.  In the show one impurity gives it the blue color that's their trademark.  Other makers even added dye (another impurity) to mimic their product. StuRat (talk) 00:07, 11 December 2014 (UTC)

Swimming owl
Recently, a video of an owl swimming in Lake Michigan has become very popular. I am looking for peer-reviewed research publications about swimming behavior of owls or other similar large raptors. I'm sure I can find a few on my own, but it seems fitting that the reference desk should collect such links for the archives!

What books, nature documentaries, or research publications have documented such swimming behavior in the past? Nimur (talk) 02:41, 6 December 2014 (UTC)


 * In the video they mentioned the owl had been forced out of the air by two falcons, so the behavior might not be normal. μηδείς (talk) 18:31, 7 December 2014 (UTC)

Stars
At the moment here in the northern latitudes (UK), there are only two stars visible in the sky. One is reddish, which I guess must be Mars, and the other is much brighter, which I at first thought would be Venus, but it couldn't be, as it should be on the other side of the planet at 4am. What is it? KägeTorä - ( 影 虎 ) ( Chin Wag )  03:54, 6 December 2014 (UTC)
 * Apparently it's Jupiter, which according to some site I found through Google (not pasted here because they want money) is shining brightly from late evening until near sunrise. ←Baseball Bugs What's up, Doc? carrots→ 05:31, 6 December 2014 (UTC)


 * "This is the first of several great months to observe Jupiter.  It now lies in Leo and so is still high in the ecliptic and hence, when due south, at an elevation of ~55 degrees." Jodrell Bank Centre for Astrophysics - The Night Sky December 2014.  Alansplodge (talk) 15:18, 7 December 2014 (UTC)
 * I don't want to be picky, but Mars and Venus are planets, not stars. --2.245.110.84 (talk) 22:32, 8 December 2014 (UTC)

Anorectic stimulants and Gastric symptoms
Why would some Anorectic Stimulants cause Gastric symptoms (Such as Constipation\Diarrhea) to some people? what are the proposed mechanisms? Thx. Ben-Natan (talk) 05:55, 6 December 2014 (UTC)


 * This is a hugely hugeulant subject, as you will have seen, having read the article you linked to. Medicines that effect the gastointestinal system have effects on the gastrointestinal system.  I have chronic gastroinstestinal issues, and have had several major surgeries and spent about a year in the hospital over the last 15 years because of it.  My doctors are almost always clueless.  Most of my medicines have side effects worse than the issue they are meant to cure (see also, rebound effect), which seems to be part of the complexity of the gut and our primitive understanding of it  (See also, gut brain).  We can probably give better references with a more specific question, and getting a professional opinion is always "best". μηδείς (talk) 20:26, 6 December 2014 (UTC)

How many kilometres per hour does the earth orbit around the sun at?
How many kilometres per hour does the earth orbit around the sun at?Whereismylunch (talk) 06:02, 6 December 2014 (UTC)


 * From Earth's orbit, around 30 km/s on average - this will vary depending on where in the orbit the planet is.Phoenixia1177 (talk) 06:06, 6 December 2014 (UTC)


 * The Galaxy Song is an easy way to remember everything your likely to want to know.--Aspro (talk) 07:11, 6 December 2014 (UTC)


 * (See Galaxy Song for some refinements.)--Shantavira|feed me 09:03, 6 December 2014 (UTC)


 * This was answered explicitly in miles per hour within the last month. If the radius of the Earth's orbit is 93 million miles on average, and there are 88/55 kmph per mph, is further help needed? μηδείς (talk) 00:50, 7 December 2014 (UTC)


 * Not sure what your 85/55 is referring to. As mentioned above, Earth's orbital speed is about 30 km/s, which is 67,000 miles per hour or 108,000 kilometers per hour.  Dragons flight (talk) 19:11, 7 December 2014 (UTC)


 * ... and, of course, it varies slightly depending on Earth's position on its elliptical orbit.   D b f i r s   20:39, 7 December 2014 (UTC)


 * My answer was given on average. The simple thing is to check wolfram alpha for earth's orbital speed in kmph.  But given the average earth to sun radius is 93 million miles, that gives a circumference in miles of 2πr, which divided by 365.25 will give an approximate distance in miles per day.  Divide that by 24 to get miles per hour.  Multiply that by 88/55 to get kmph.  This is about 5th grade level math, certainly well pre-algebra.  This will give you a good average number, since as mentioned above, the velocity is not perfectly constant.  See Kepler's Laws for the complications. μηδείς (talk) 22:45, 8 December 2014 (UTC)


 * That's twice you've given the conversion factor from kilometers to miles as 88/55. That's not even in lowest terms!  If you want to work to only 2 significant digits, why not just say 1.6?  (The accurate conversion factor is 1.609344, by the way.)  And for that matter, why work in miles at all instead of just starting with the radius in kilometers, given here?

This NASA page gives the average orbital velocity of the Earth as 29.78 km/s (which is 107,200 km/h) and also shows the extreme values. It ranges from 29.29 to 30.29 km/s (105,400 to 109,000 km/h). Under Kepler's Second Law, the orbital velocity is higher when the Earth is closer to the Sun (currently it's closest&mdash;at perihelion&mdash;in early January; see here) and lower when it is farther away (it's farthest&mdash;aphelion&mdash;in early July). --65.94.50.4 (talk) 18:47, 10 December 2014 (UTC)

Thermal resistivity of tungsten/molybdenum alloy (Dowmo alloy)
Does anyone know where I can find data on the thermal resistivity or thermal conductivity of 50:50 tungsten/molydenum alloy? I need data over the range 300 to 1300 K. I know it's about the same as tungsten at the high end of the range, so a figure for even just a single low temperature point would help. I found nothing by googling. 124.182.163.187 (talk) 14:12, 6 December 2014 (UTC)
 * Slug manufacturers commonly provide very detailed datasheets on request so you should search for some manufacturer who is offering exactly this alloy and request it. --Kharon (talk) 00:37, 7 December 2014 (UTC)
 * What do you mean by "slug"?  I tried some time ago emailing a Chinese manufuacturer and an American manufacturer of MoW alloy wire.  In both cases they never replied.  The American manufacturer has datasheets for their various alloys on their website that you can download, but they don't give the thermal resistivity or conductivity. 58.167.234.9 (talk) 01:09, 7 December 2014 (UTC)


 * Did you try this company who seem to know a bit about what they are talking about? I would generally recommend phoning up a company like this and trying to talk directly to someone technical as the chances of people answering general web enquiries being able or willing to get answers to difficult questions are not high in my experience. I've also googled without finding anything. It isn't in the very comprehensive old report - 'The engineering properties of molybdenum and molybdenum alloys', 1963, DMIC. Maybe you could look in 'Thermophysical Properties of Matter Volume 1: Thermal Conductivity: Metallic Elements and Alloys', Y. S. Touloukian et al. JMiall  ₰  00:43, 8 December 2014 (UTC)
 * Thanks. The company I tried was another one.  Interesting side issue - on the page you linked, they state that electrical resistivity of MO-W alloys is minimum when the mix is 50:50.  It surely should be the conductivity is minimum with 50:50....  I'll follow up on the Touloukian book. 124.178.179.253 (talk) 02:35, 8 December 2014 (UTC)
 * I'm not a chemist or metallurist so don't know the right equations to use but:
 * if the alloy acts like a pair of resistors in parallel so 1/R = 1/R1 + 1/R2 with both R1 and R2 being of the form (ax+b), where x is the fraction of that component, then you'd get a curve with a maximum/minimum at 50%ish if the properties of the 2 individual components were about the the same (which they are).
 * I could imagine a structure with stronger electrical linkage between different atom types than ones of the same type. In a substitutional alloy I'd assume you'd then get maximum linkage at 50-50. JMiall  ₰  21:52, 8 December 2014 (UTC)
 * I'm not a chemist either, but applying simple rules like you've suggested in general doesn't seem to work with metal alloys. I know it does depend on the relative solubilities.  You get essentially 4 types of phase diagram depending whether a)the two metals are completly soluble in each other, b) they are totally insoluble in each other, c) they are soluble in each other in the liquid pahse but not the solid pahse, and d) they are partly soluble in each other in the solid phase.  Most electrical engineers like myself know about (d), as it gives a phase diagram known as 'eutectoid' for which the best known example is lead+tin (solder).
 * How alloys behave wrt electrical conductivity, thermal conductivity, thermal expansion etc correlates with the phase diagram, but if there is a way to calculate the properties, accurate enough for engineering purposes, of an alloy knowing the properties of its constituent metals, I've never seen it.
 * I've checked Touloukian. It doesn't have data for MoW 50:50, but it does have 70:30.  I've discovered a paper in the Russian journal 'High Temperature' has a relavent article, Zarichnyak Y P in vol 15:4 1978, but I can't get hold of it.  None of the local university libraries have it. 124.178.179.253 (talk) 04:26, 9 December 2014 (UTC)

Why 4 contact points in battery?
Why do cell-phones' batteries and laptop batteries have more than 2 contact points? — Preceding unsigned comment added by Noopolo (talk • contribs) 19:10, 6 December 2014 (UTC)
 * AFAIK (and supported by simple search but unlinked because I'm on a mobile device) the 3rd contact which has been common since long before the smart phone era is generally for a thermistor to help in regulating dis/charging and so stopping the battery from the infamous venting with flames. The fourth which is much more recent and not even present on many smart phones is probably for the NFC antenna. Nil Einne (talk) 19:24, 6 December 2014 (UTC) (EC) P.S. I'm thinking phones here. I'm not that familiar with laptop batteries except to know they often have 3 or more cells (traditionally 18650 or similar depending on size although I imagine that's changing). While the cells are in parallel edit:sorry meant series it's generally best practice to monitor each individuually. You may also use more than one thermistor. However more of the smart circuitry may be embedded in the battery pack so the terminals may be for power and connection to the smart circuitry Nil Einne (talk) 19:33, 6 December 2014 (UTC) (edit2) It's possible the third terminal on a phone battery may also be for embedded smart circuitry rather than a simply a thermistor Nil Einne (talk) 19:40, 6 December 2014 (UTC)
 * (ec) Many modern batteries contain on-device digital logic to check battery status, battery temperature, and to communicate with the charger and the load to more efficiently control current and voltage. There are innumerable standards and proprietary systems that implement such features, and their principle of operation varies widely.  Are you looking for information about a specific battery type?  Nimur (talk) 19:26, 6 December 2014 (UTC)
 * It varies, but typically the extra contacts are used for sensors such as temperature. The sensors are necessary because lithium batteries can be dangerous -- even catch fire and/or explode -- if charging is not carefully controlled. Do a search on 'laptop battery contacts' (without the quotes) for more. Short Brigade Harvester Boris (talk) 19:27, 6 December 2014 (UTC)

@Nimur: no concrete battery in mind. Just wondering whether a standard interface was available. That would allow for interoperability among different devices. You could take a cell from your laptop and use it in the cell-phone, if needed. Thing like that. — Preceding unsigned comment added by Noopolo (talk • contribs) 19:25, 7 December 2014 (UTC)
 * Batteries tend to be designed and manufactured for a specific application, so a common connection is not considered desirable because there would be safety issues if an unsuitable battery was fitted (look for stories of exploding batteries). Your laptop battery probably supplies 19 volts which is totally unsuitable for your cellphone.  Perhaps in the future there will be some standardisation of similar batteries, but manufacturers don't seem to regard it as a priority at present.    D b f i r s   20:36, 7 December 2014 (UTC)
 * There is an i2c bus to the battery. It can be queried (from memory) for its: nameplate capacity, capacity at first full charge, capacity at last full charge, current capacity. CS Miller (talk)