Science desk
< October 16	<< Sep \| October \| Nov >>	October 18 >

Welcome to the Wikipedia Science Reference Desk Archives
The page you are currently viewing is an archive page. While you can leave answers for any questions shown below, please ask new questions on one of the current reference desk pages.

October 18

Cobalt chlorides

Does cobalt form any higher chlorides than cobalt(II) chloride? I have reason to suspect that it does.

Cobalt(II) chloride is reacted with sodium hydroxide to get cobalt(II) hydroxide, a blue solid. It is heated to obtain the red form.
The cobalt(II) hydroxide solid is reacted with hydrogen peroxide to obtain a tan-brown solid. Some fizzing is apparent, which is likely from catalytic decomposition of the hydrogen peroxide.
The brown solid is reacted with hydrochloric acid to make a pink-brown solution.
The pink-brown solution is reduced by ascorbic acid to obtain a red-pink solution typical of cobalt(II) chloride.

What is that pink-brown solution? I would assume the brown solid is cobalt(III) hydroxide.

Thanks, Chemicalinterest (talk) 00:54, 17 October 2010 (UTC)[reply]

~~Probably hexaaquacobalt(III). I'm having trouble finding images, but I think this is one: [1]. If you google translate the page, you can get a pretty good idea what's going on.~~ Buddy431 (talk) 01:50, 17 October 2010 (UTC)[reply]

Wait, hexaaquacobalt(III) is blue, but the hexaaquacobalt(II) is pink. It could just be excess cobalt(II) that wasn't oxidized by the peroxide. The "red form" that you speak of is almost certainly the hexaaquacobalt (II) complex (you can just dissolve cobalt(II) chloride in water to get the same thing; I'm not sure why you react it with hydroxide first) (The red form is beta-cobalt(II) hydroxide, while the blue is the alpha form. Not sure what the difference is).

Yeah, I'm really wondering how efficient your oxidation was. You can oxidize cobalt(II) to cobalt(III) very efficiently in the presence of ammonia (and other amines), but it's harder without them. Buddy431 (talk) 02:30, 17 October 2010 (UTC)[reply]

Just a guess, but the difference between the red form and the blue form of the hexaquacobalt(II) ions is likely due to coordination geometry. That is, the way in which the water ligands bond to the cobalt atom determines the "alpha" and "beta" forms, and also likely causes the color difference. --Jayron32 03:02, 17 October 2010 (UTC)[reply]

I think that he's referring to a solid hydroxide precipitate (I made that mistake earlier as well). It looks like the alpha and beta forms have different crystal structures. 87.102.13.111 dug out this article [2] last time we had a question like this in June. I think that hexaaquacobalt(II) is always pink (that's the "red-pink solution typical of cobalt(II) chloride" that ChemicalInterest mentions at the end). Hexaaquacobalt(III) is harder to prepare, but it's definitely blue: [3]. I'm still betting that the "pink-brown" solution that he made has unoxidized cobalt(II) (forming the pink hexaaqua complex), but I'm open to other suggestions on the matter. Buddy431 (talk) 04:03, 17 October 2010 (UTC)[reply]

You're in high school, right? Making cobalt(III) complexes is a pretty standard lab experiment in Freshman general chemistry. If you have access to academic journals, there's a lot of stuff about them. Here's a pretty good one, looking at this as a teaching exercise: [4]. I had to go through something like this not too long ago, so if you're really interested, I can point you in the direction of lots of other resources as well. Buddy431 (talk) 02:06, 17 October 2010 (UTC)[reply]

Yes. One of the articles states that Co(III) is unstable in water solution. I don't know why the easily reducible "pink-brown solution" didn't oxidize the HCl that was added. I produced Co₃O₄ and it easily oxidized HCl to Cl₂ gas. --Chemicalinterest (talk) 11:34, 17 October 2010 (UTC)[reply]

How did the possibly cobalt(III) brown solid get reduced to the cobalt(II) chloride in solution without releasing chlorine gas? Or is there a cobalt chloride actually stable in hydrochloric acid solution? --Chemicalinterest (talk) 11:39, 17 October 2010 (UTC)[reply]

Do you test the pH of your solutions? The behaviour of a complexed ion is at least slightly different from say, a "naked" one in solution. Does Co(III) oxidise all chlorides, or just HCl? John Riemann Soong (talk) 14:47, 17 October 2010 (UTC)[reply]

Probably around 0, becaue I added excess hydrochloric acid, hoping for it to produce chlorine. --Chemicalinterest (talk) 11:07, 18 October 2010 (UTC)[reply]

Controlled mass loss of Earth.

QUESTION:

If planet Earth suffered a continuous internal MASS LOSS with no related inertial effect (as in the case of the material passing through an interdimensional window) what would be the Earth's orbital perturbation, right up to the end?

October 16, 2010

K. McIntire-Tregoning, concert composer email: <email removed> <invalid copyright claim removed> —Preceding unsigned comment added by 189.173.206.175 (talk) 01:03, 17 October 2010 (UTC)[reply]

That makes no sense. Mass = inertia, they are not seperable concepts, so if the earth lost mass through ANY process, there would be a resulting change in motion of the earth, and between the earth and all objects gravitationally bound to it. If mass were lost, the earth would start moving faster to compensate for the mass loss, per conservation of momentum. This increase in speed would cause the earth to drift outward in its orbit per conservation of angular momentum. --Jayron32 01:38, 17 October 2010 (UTC)[reply]

I agree that the question makes no sense, but the elaboration here is not relativistically sound. If the earth lost mass but was required to preserve its momentum, observers at different (slow) velocities should observe it accelerating in different directions. Actually, conservation of mass/energy and conservation of momentum are components of a single four-dimensional conservation law in special relativity, so if you see mass disappearing into nowhere you might as well wave goodbye to momentum conservation too.

The basic framework of special relativity could hold even in the absence of energy-momentum conservation, but in general relativity I think it follows deductively from Einstein's equation that energy and momentum are conserved locally, full stop. –Henning Makholm (talk) 03:43, 17 October 2010 (UTC)[reply]

The questions sounds like the mass is going from the inside of the Earth to some other dimension. The "no inertial effects" might mean just that the mass is not being shot from a gun or blown off the planet by a Darth Vader device causing an internal explosion. No "action=reaction" process moving the remainder of the Earth. If the mass just disappeared and the planet became less massive, wouldn't the Earth remain in the same orbit around the sun? I suppose the center of mass of the Earth-Sun couple would shift toward the Sun, and the Sun would wobble less annually, while the center of mass of the Earth-Moon couple would shift toward the Moon and the Earth would wobble more every lunar month. If the Earth were reduce to the mass of a grapefruit, would it orbit the Moon, or crash into the Moon? Wouldn't the Moon+ Tiny Earth system still be the same mean distance from the Sun? Edison (talk) 03:40, 17 October 2010 (UTC)[reply]

My conclusion is similar to Edison's which assumes that earth mass disappears taking its momentum with it. The Earth would crash into the Moon when the center of mass of the Earth-Moon couple shifted to slightly above the surface of the Moon. If the Earth-Moon orbits were circular it would happen at exactly the Moon's surface but the actual elliptical orbits will cause the crash to happen sooner, and in any case long before the Earth has shrunk to grapefruit mass. Cuddlyable3 (talk) 14:31, 17 October 2010 (UTC)[reply]

The best theories we have answer such questions by saying that it isn't going to happen. It is theoretically impossible for mass to disappear from the planet without going off in some particular direction.

"Theoretically impossible" does not mean that it is necessarily isn't going to happen in reality. But it means that if it does happen in reality, science will be unable to predict anything about what happens next. The theory simply gives up at that point (it's not as if anybody would care what a theory that had just been exposed as a fraud would predict anyway). Hell might freeze over, pigs might fly. We'll just have to wait and see. –Henning Makholm (talk) 03:51, 17 October 2010 (UTC)[reply]

I have removed the copyright notice as it is invalid. Please note as it is made clear every time you edit a page, you agree to release any and all of your textual contributions under the Terms of Use which means that you release your contributions under a joint GFDL and CC-BY-SA licenses. You cannot therefore reserve all rights as anyone can re-use your contributions in accordance with the terms of the licenses you agreed to release them under. You do maintain the copyright for your contributions, but there is no need to mention your copyright as it's irrelevant (attribution is provided for under the terms of the licenses you agreed to). Also I see someone already removed your email address, as the header says we don't answer questions by email so the only one likely to be interested in your address are spam bots. Nil Einne (talk) 09:13, 17 October 2010 (UTC)[reply]

Obviously, the "answer" will depend on how one interprets the question. I read the poster as envisioning something like: Carve the Earth into a billion little blocks, and sequentially take one block anyway via some magical process that does not change the energy or momentum of the remaining blocks. In that scenario, the size of the Earth's orbit does not change (ignoring the moon, for the moment). The acceleration of the Earth due to the sun depends only the mass of the sun, not the mass of the Earth, and so the orbit would be unchanged due to this type of magical change in mass. On the other hand, the gravity due to the Earth would decrease, which would cause the orbit of the Moon to expand. Eventually the Moon would become the dominant object orbiting the sun (and much more strongly bound to the sun than to the Earth) and the remains of the Earth would be a small remnant orbiting the Moon at greater distance than it has today. Dragons flight (talk) 20:00, 17 October 2010 (UTC)[reply]

Why would the Earth-Moon system behave differently than the Earth-Sun system? In principle they should react in the same way to a mass decrease of Earth. Hence, when you say that Earth's orbit around the sun remains unchanged then that is only true approximately, i.e. if you neglect Earth's mass compared to the sun's mass. That is a good approximation but an approximation nonetheless. The question is a nice example of how an entire theory breaks down if one component (conservation of mass) is removed. The argument of Earth's velocity increasing because of conservation of momentum is a good one, but then so is the orbit argument. Newton's theory can't decide because it's not applicable any more. Hence the only real answer to the question can be: It ain't gonna happen, as Henning already said. --Wrongfilter (talk) 07:31, 18 October 2010 (UTC)[reply]

unprovoked reoccuring blister type lesions on feet

This question has been removed. Per the reference desk guidelines, the reference desk is not an appropriate place to request medical, legal or other professional advice, including any kind of medical diagnosis, prognosis, or treatment recommendations. For such advice, please see a qualified professional. If you don't believe this is such a request, please explain what you meant to ask, either here or on the Reference Desk's talk page.

Red Act (talk) 01:17, 17 October 2010 (UTC)[reply]

Mass of copper

what is the mass of 0.30 cm3 of copper? —Preceding unsigned comment added by 24.86.167.133 (talk) 02:15, 17 October 2010 (UTC)[reply]

The article copper has the density listed, it is the second item under "physical properties" in the infobox on the right side of the article. You can easily answer your question with that information. --Jayron32 02:20, 17 October 2010 (UTC)[reply]

I am sorry but I do not see it —Preceding unsigned comment added by 24.86.167.133 (talk) 02:25, 17 October 2010 (UTC)[reply]

Look to the right in the article copper, there is a box with a picture of a big random chunk of copper in it. Scroll down. The first section under the picture has "General properties" in black on pink background. The second section, also in black text on pink background, is titled "Physical properties". The second entry in THAT section says "Density (near r.t.)". That will help you answer your question. --Jayron32 02:29, 17 October 2010 (UTC)[reply]

what does cm-3 mean? —Preceding unsigned comment added by 24.86.167.133 (talk) 02:33, 17 October 2010 (UTC)[reply]

It means 1/cm³ or inverse of cm³. In this context, the density number is the number of grams that a 1 cm³ piece of copper would weigh. That's the definition of density, the mass of a given unit of volume. Let's rephrase the question: Let's say you are going to buy some cheese that costs $8.94 per pound, and you want to buy 0.30 pounds of it? How much will you spend? The math is identical here, just replace $/pound with grams/cm³. --Jayron32 02:37, 17 October 2010 (UTC)[reply]

so the mass of 0.30 cm3 of copper would be 44.7 g

If one cm³ has a mass of 8.94 grams, how can a smaller piece of copper weigh more? That makes no sense! --Jayron32 02:46, 17 October 2010 (UTC)[reply]

oops. I recalculated and got 2.68 g —Preceding unsigned comment added by 24.86.167.133 (talk) 02:54, 17 October 2010 (UTC)[reply]

:) --Jayron32 02:58, 17 October 2010 (UTC)[reply]

Thank you! —Preceding unsigned comment added by 24.86.167.133 (talk) 03:01, 17 October 2010 (UTC)[reply]

Flatulence smelling

For many people, smelling one's own flatulences is enjoyable - many people I know also admit enjoying the smell of their flatulences under the blankets while in bed. Is this a documented phenomenon? I've seen monkeys smell their own feces immediately after defecation - probably for monitoring health (?), is the flatulence smelling a derivative of this? Thanks, Gil_mo (talk) 08:16, 17 October 2010 (UTC)[reply]

Cats behave similarly. In their case it is to aid in covering over their stools to hide their presence from other animals. Cuddlyable3 (talk) 14:18, 17 October 2010 (UTC)[reply]

This question has been asked several times before. Try searching the archives.--Shantavira|^{feed me} 14:36, 17 October 2010 (UTC)[reply]

http://www.last-word.com/content_handling/show_tree/tree_id/3432.html 92.15.20.132 (talk) 16:08, 17 October 2010 (UTC)[reply]

pressure exerted by expanding ice

Suppose I have a plastic container full of water that ruptures in a freezer set at -20C but not -17C. Does this tell me anything about the strength of the container? Since stress is likely to be involved, suppose failure is by a small hole in the centre of the lid and crystal growth is observed through the hole -- the entire lid is covered with crystals (water that was expelled?).

In a real-life scenario I suppose sublimation would occur. If supercooled water cannot turn to ice because of pressure, is its vapor pressure likely to increase? John Riemann Soong (talk) 09:25, 17 October 2010 (UTC)[reply]

I read from google that ice can exert 2040 atm at around -22C or something...does this mean I can form ice III by simply pouring water into a strong enough container (to the brim) and putting it into a freezer? (My lab also has an -80C freezer...) To what extent does adding salt to the water decrease the expansion pressure of ice? I assume that concentrated salt water that freezes at say -19C, exerts 0 atm of pressure at that pressure, but does its "curve" (rate of pressure increase with decreased temperature) differ in slope? John Riemann Soong (talk) 09:38, 17 October 2010 (UTC)[reply]

Have you looked at a phase diagram for water?Smallman12q (talk) 23:33, 17 October 2010 (UTC)[reply]

mmhmm! I have trouble working out the scenario where the ice exerts a pressure on the environment versus the environment exerting the pressure on the ice. The latter scenario is what the phase diagram covers. John Riemann Soong (talk) 00:39, 18 October 2010 (UTC)[reply]

Have a look here and at http://www.igsoc.org/journal/56/196/j09J067.pdf.Smallman12q (talk) 11:46, 18 October 2010 (UTC)[reply]

caffeine

Is caffeine a vasodilator or a vasoconstrictor? —Preceding unsigned comment added by Kj650 (talk • contribs) 17:02, 17 October 2010 (UTC)[reply]

Our article says that it is a vasoconstrictor, though it's kind of hidden. The reference comes from here. Matt Deres (talk) 17:10, 17 October 2010 (UTC)[reply]

why have i heard that it is a vasodilator then. —Preceding unsigned comment added by Kj650 (talk • contribs) 17:23, 17 October 2010 (UTC)[reply]

example

http://answers.yahoo.com/question/index?qid=20081122193010AAkTErG —Preceding unsigned comment added by Kj650 (talk • contribs) 17:23, 17 October 2010 (UTC)[reply]

I thought it was a vasodilator because it breaks down to theobromine which competes with adenosine -- another vasodilator. Regards, --—Cyclonenim | Chat 18:39, 17 October 2010 (UTC)[reply]

Theobromine is a vasodilator, but as our caffeine article section on metabolism mentions, only 12% of the product of caffeine metabolism is theobromine (Googling suggests it's not a straightforward thing, though, with paraxanthine being both another product of caffeine and an intermediary to theobromine). Paraxanthine is the primary product (~84% of the caffeine), so I assume it is a vasoconstrictor, but several minutes of Google book and web searching hasn't given me a definitive answer on that. Clearly, both our caffeine and paraxanthine articles could use some more referencing. Matt Deres (talk) 21:45, 17 October 2010 (UTC)[reply]

Caffeine is a vasoconstrictor. In cases like this, it's best to go directly to research articles, rather than rely on secondary sources. Here are two research articles that provide direct evidence for caffeine being a vasoconstrictor: [5] [6] You can find additional evidence with this Google Scholar search[7] Red Act (talk) 19:40, 17 October 2010 (UTC)[reply]

Carbon monoxide detector

Last weekend I was out with my family for the day. When we returned at night we found our carbon monoxide detector sounding alarm. I went inside and found that one of the burners on the gas stove was left on (at the lowest setting) for the ~12 hours that we were gone. Since I figured that this was a very small source of carbon monoxide and our house is large (~3000 sq ft), I felt there was little risk. I opened the windows and within minutes the alarm stopped sounding. We left all the windows in the house open for several hours (it was a breezy day, too), just in case. When I mentioned this to a neighbor the other day, he was absolutely horrified and said that we were lucky to even be alive. We should have immediately called 911 and stayed out of the house until it was cleared for occupancy by emergency personnel, he insisted. One small burner in a large house seemed such a trivial problem to me that I felt perfectly comfortable with what I did. Was there any real danger? Was my neighbor right, did I make a mistake? Edgeweyes (talk) 18:30, 17 October 2010 (UTC)[reply]

The detector detects the concentration of CO at the location of the detector. That means, if your house is 10x as large as someone else's, its alarm would indicate (on average) 10x the total amount of CO in the house, not the "same amount, diluted into a 10x larger space". I don't know the level at which your alarm responds (conservatively just below actual dangerous level so you have time to react and leave before dying?), and obviously it's only sensing CO where it is rather than the whole house or somewhere else in it you might stand. You're alive because--luckily--the area you were did not have an amount that was high enough to be dangerous for a single wiff. DMacks (talk) 18:56, 17 October 2010 (UTC)[reply]

BTW it's not normal for a burner left on for 12 hours on low to raise CO levels at all, you need to figure out why that happened. As for your question, since the CO detector stopped right away, I probably would have done the same thing - after the fact. But before the fact, as soon as I (you) heard the CO detector, you should have immediately left, and not waited to open windows or figure out what the problem was. That was where your mistake was. Once the detector stopped, opening the windows and the other things you did was fine - but you should have stopped much earlier, you should have left instantly upon hearing the alarm. Ariel. (talk) 19:14, 17 October 2010 (UTC)[reply]

Are you sure that a normal-functioning gas stove shouldn't produce detectable levels of CO? The instructions that came with the alarm say that it must not be placed within 15 feet of a gas stove or it will give a false alarm. CO from a stove seems to be expected. Edgeweyes (talk) 23:48, 17 October 2010 (UTC)[reply]

Yes, I'm quite sure. But I didn't say "detectable levels", I said "raise levels" - your stove raised levels in your entire house! That is very not normal. You may have a problem with your stove, or perhaps insufficient airflow in the house. If a fire on low can use up all the oxygen in the house, then several people in the room can do the same. You need to figure out what happened. Ariel. (talk) 13:50, 18 October 2010 (UTC)[reply]

CO detectors generally have multiple thresholds actually. The details depend on the nature of the sensor, but generally you can expect at least both an acute toxicity alarm (e.g. brief detection of very high levels) and a persistent toxicity alarm (e.g. detection of a low level hazard for tens of minutes). The fancier alarms provide a method of telling the difference, such as a display or a different sounding alarm. Persistent low levels of CO (e.g. 0.01% of air) will cause headaches and sometimes nausea, but aren't life threatening. Acute toxicity can lead to unconsciousness and death (e.g. 0.1% of air). Concentrations above about 1% of air can cause immediate unconsciousness after only a few breaths and death after 3 minutes. If the original poster knew for sure that it was a low-level hazard then there is nothing wrong with entering the area and ventilating. However, it seems like he was only guessing, which is risky, since he could have gone in, passed out, and not been able to get out if the levels were high enough. Dragons flight (talk) 19:40, 17 October 2010 (UTC)[reply]

I'll go with the others on this one: if you need to ask the question, then you should have called the fire brigade and waited for someone with breathing apparatus and a professionally calibrated CO meter to go in and open your windows for you. The detectors are usually set at a very low level: the PEL in the U.S. is 50 ppm (30 ppm in most of Europe), but that is a level you are supposed to be able to breathe for 8 hours a days while working and not come to any harm. You can get to those sorts of levels on a busy city street in summer if there's little or no wind – I know, because I've worked with carbon monoxide a lot and have had access to proper meters, so I took the meter downtown one day to see what the levels actually were outside! The fact that the house is large is irrelevant – it is the concentration of carbon monoxide in the air which determines the danger. Indeed, a large house will take longer to fully ventilate than a small flat. The fact that it took minutes for the alarm to stop indicates that you actually had quite a bit of CO in there, although it depends on the design of the alarm as well. I'd say you're lucky to have the alarm, otherwise you could have given yourselves a pretty nasty headache (standard symptom of mild CO poisoning) without knowing why, and it could have been even worse if you'd have gone to bed straight after coming home. Physchim62 (talk) 21:51, 17 October 2010 (UTC)[reply]

The instructions that come with the alarm state that the sensitivity is 30 ppm. Since only a few minutes of ventilation brought the levels low enough to stop the alarm, this suggests that the CO levels were close to levels that are acceptable (near or below the PEL). But I take to heart the comments above that I couldn't have known this at the time. I'm curious about your statement, "The fact that the house is large is irrelevant". If the same burner were left on in a small one-room flat, wouldn't the CO levels have become much larger than they did in my larger home? Edgeweyes (talk) 23:39, 17 October 2010 (UTC)[reply]

When I said the size of the house is irrelevant, I meant irrelevant in terms of the decision you had to make as to whether to go in or not. Actually, it's not completely irrelevant: a larger house can be riskier than a small flat in terms of that decision. All you knew on the outside was that there was an alarm telling you there was a dangerous level of CO inside: you didn't know what the level was, and I'll assume you don't have any specialist experience that might have allowed you to make an educated guess. If you had that sort of knowledge, you wouldn't have to ask your question here, because you would be clear in your calculation of the risk involved.

So you went in not knowing if it was 40 ppm, 400 ppm or 4000 ppm, and probably not knowing what levels of risk are associated with each of those figures. In terms of chemical safety, that's the error you made; thankfully without any consequences other than your standing with your neighbour! I would guess the levels were much nearer to 400 ppm than 40 ppm, and quite possibly even higher in the room where the stove was; but that's just a guess based mostly on multiple experiences of how quickly CO clears from small laboratories when the chemist working there (yours truly) does something he shouldn't have done with the cylinder or the supply line. In general, because it has almost exactly the same density as air, CO clears pretty quickly once you have adequate ventilation.

I said a large house can be more dangerous than a small flat because, if the house is large, you have to spend more time breathing the contaminated air while you find the source of the CO, and you're further away from clean air outside. A one-off few minutes in an atmosphere of 400 ppm CO isn't going to do you much harm, nor is a one-off few seconds in an atmosphere of 4000 ppm (based on hemoglobin CO binding rates from NIOSH and a large safety margin). A few minutes at 4000 ppm and you would almost certainly start to notice it, and possibly be in quite serious trouble. Physchim62 (talk) 02:25, 18 October 2010 (UTC)[reply]

Thanks for the detailed response. Edgeweyes (talk) 12:05, 18 October 2010 (UTC)[reply]

CO detectors I have owned provide a display. Has the OP stated what the displayed level actually was? I expect that most "fire brigades" or firefighters would be happy to check out possible CO poisoning situations, rather than carrying out the corpses later. Leaving a burner on at the lowest setting is like having a pot on to simmer all day, common in households for many decades/centuries/millenia. The problem now might be modern houses that are sealed up tight, without drafts bringing in fresh air. Edison (talk) 02:06, 18 October 2010 (UTC)[reply]

My CO detector does not have a display. --Chemicalinterest (talk) 11:05, 18 October 2010 (UTC)[reply]

The detector in this case simply displays a little green LED or a little red flashing LED. Edgeweyes (talk) 12:05, 18 October 2010 (UTC)[reply]

CO is a bit lighter then air, is your CO detector located on the ceiling like a smoke detector? Googlemeister (talk) 13:39, 18 October 2010 (UTC)[reply]

Mine has a red and green LED and says CO detector right on it. --Chemicalinterest (talk) 14:20, 18 October 2010 (UTC)[reply]

"CO is a bit lighter then air" at some temperatures (cross-over/equivalence is right around room temp), if we believe the actual density values in carbon monoxide and density of air rather than ideal-gas approximations. DMacks (talk) 16:41, 18 October 2010 (UTC)[reply]

Papillomaviruses stable for months??

I was recently reading the article plantar wart (a sort of recurrent blister-like lesion on the feet caused by human papillomavirus 1), which cites a medical-reference type source that claims that the virus can survive for months without a host.[8] (I'm not entirely sure it's true though - PMID 20189438) I find this interesting, because although there has been some difficulty involved,[9] it is possible to package plasmid DNA in HPV particles.[10] It seems to me that for the amateur DIYbio crowd that a particle which could survive on a floor for months might well last for many years in a microcentrifuge tube with the right buffer, even at room temperature, yet still be ready to transfect mammalian cells - liberating the users from the expense and trouble of -80 C storage.

Does anyone know whether the stability of DNA in papillomavirus vectors at room temperature has been tested? Wnt (talk) 20:25, 17 October 2010 (UTC)[reply]

That's an odd way to describe verrucas: I've never seen one that could be mistaken for a blister, and would be very surprised to hear someone describe one as 'blister-like'. They are quite different to blisters. Perhaps you've never had one? 109.155.37.180 (talk) 01:15, 18 October 2010 (UTC)[reply]

The one I had was like a roughened callus with a blister-like hollow in the center, which deepened for some time until it was about the depth of a thumbtack. The picture in the article looks blister-like also. It seemed a fair comparison to me. Wnt (talk) 09:00, 18 October 2010 (UTC)[reply]

Killing Me Softly With a TV

It's common trope in TV and movies to kill someone by tossing a TV/radio/hair dryer/whatever into a bathtub while that person is sitting in it. But why would that work? It seems to me that the "shortest" path for the electricity would be for it to exit through the ground wire of whatever appliance is involved. If I'm not grossly mistaken, the situation could be conceptualized as an effectively infinitely parallel series, and in that case the human body is not an attractive path for the electrons. 96.246.58.133 (talk) 20:32, 17 October 2010 (UTC)[reply]

I agree. But there's only one way to find out for sure; wait until a more knowledgeable Wikipedian bestows their wisdom upon us. :) --90.215.213.167 (talk) 20:50, 17 October 2010 (UTC)[reply]

MythBusters to the rescue: according to MythBusters (2004 season)#Appliances in the Bath, it is possible in some circumstances. And of course some TV shows can leave you brain dead. Clarityfiend (talk) 21:11, 17 October 2010 (UTC)[reply]

Some of the current from the hot or "phase" wire would return through the neutral connection in the submerged appliance, but some would return through the earth ground connection provided by the tub and its water pipe and drain connections, likely sufficient to kill anyone in said tub full of water. Electricity does not follow an "either or" route; the current divides in proportion to the path impedance. It does not take much current to kill an animal. Ground fault outlets are required by electrical codes in many jurisdictions for kitchens and bathrooms. Their function is to turn off the current very quickly if electricity from the hot wire does not all return on the neutral wire, thereby reducing the chance of electrocution. Edison (talk) 01:51, 18 October 2010 (UTC)[reply]

If I recall the mythbuster episode in question, bathsalts in the water made it far more likely you get fried then plain old water. Googlemeister (talk) 13:34, 18 October 2010 (UTC)[reply]

Absorb my frameshifts

If a frame shift occurs within an exon, will exons downstream by transcribed correctly or not? Does it depends on whether the two exons share code for a single residue (i.e. two bases from one exon and one from the other encoding a particular residue) --90.215.213.167 (talk) 20:49, 17 October 2010 (UTC)[reply]

By definition, a frameshift mutation will alter the reading frame in all exons subsequent to that position. However, this generally results in early termination due to a stop codon in the new reading frame. --- Medical geneticist (talk) 02:05, 18 October 2010 (UTC)[reply]

Have you ever thought of how great a name like The Frameshift Mutations would be for a band? John Riemann Soong (talk) 02:25, 18 October 2010 (UTC)[reply]

Generally speaking, the splicing precedes the translation. So when the translation frame turns out to be altered at the ribosome, it's much too late to adjust the splicing to match. Now there are aberrations - situations where a ribosome is supposed to stop, but one way or another it can end up frameshifting, and so in theory the mutation might potentially be compensated, but it would only be to a fractional extent. See PMID 2207158 for an example. Wnt (talk) 09:10, 18 October 2010 (UTC)[reply]

I suppose that another exception would be if the frameshift mutation occurs within an alternatively spliced exon such that the splicing machinery "skipped" that exon under certain conditions. This would allow the transcriptional machinery to bypass the frameshift mutation. --- Medical geneticist (talk) 12:29, 18 October 2010 (UTC)[reply]

Amount of energy required to boil water

Quick question: how much energy is required to bring, say one litre of water from room temperature to 100C, but not actually turn it into steam? (I assume the amount of energy required increases linearly with the volume of water, yes?). If you're wondering, I was idly trying to work out the efficiency of my kettle. Thanks, --HarmoniousMembrane (talk) 20:50, 17 October 2010 (UTC)[reply]

4.2 joules per gram per degree Celsius, or 1 calorie (with a small c) per gram per degree Celsius. The latter is how the calorie was originally defined. The figure varies slightly with temperature, but I guess that should be accurate enough for your calculation ;) Physchim62 (talk) 21:19, 17 October 2010 (UTC)[reply]

To be clear though, boiling water is turning it into steam (which requires a lot of energy, when compared to just heating the water up). Even if you bring your water to just below boiling, some of the water will evaporate at a temperature below 100 C, "stealing" some energy with it. I'm not sure how significant this is though in the total amount of heat needed. Buddy431 (talk) 21:24, 17 October 2010 (UTC)[reply]

I agree with Physchim62's figure. One litre of pure water has a mass of one kilogram so raising the temperature of one litre of water from 15C to 100C requires 357 kJ of energy (4.2 x 85 degrees x 1000 g). If your kettle is electric with an element rated at 1 kW, it should take 357 seconds for the mean temperature to reach 100C. (It may take quite a few seconds longer for the kettle's thermostat to turn it off.) Dolphin (t) 22:21, 17 October 2010 (UTC)[reply]

Where I live, room temperature is unlikely to be as low as 15°C; it's more likely in the range 20°C to 25°C, and higher if it's summer and the place isn't air-conditions. On the other hand, tap water in most places is likely to be well below room temperature. In any case, it's obvious how to adjust the calculation. --Anonymous, 03:39 UTC, October 18, 2010.

Also depends on altitude (or more specifically, atmospheric pressure). At very high elevations, the boiling point is noticeably lower than 100 °C. Still takes approximately the same amount of energy (Joules per degree per gram) to heat the liquid but less to get "to the boiling point" because the number of degrees from room temp is smaller. DMacks (talk) 04:18, 18 October 2010 (UTC)[reply]

However, the original poster did meantion 100°C rather than "the boiling point". --Anon, 05:47 UTC, October 19, 2010.

Umm, why are people able to help the OP with thermodynamics of boiling water but not me with the thermodynamics of freezing water? John Riemann Soong (talk) 22:41, 17 October 2010 (UTC)[reply]

Have you considered that maybe, just perhaps, you're putting larger demands on the reference desk's resources than it is up to handling? There is, as far as I know, no rule against starting more than one question thread per day on average, but since the desk runs on voluntary labor, everyone gets to decide for themselves what they consider a productive use of their time. –Henning Makholm (talk) 23:07, 17 October 2010 (UTC)[reply]

(ec) John, your question above is appreciably more difficult. Please remember that other editors here are volunteers; we're not paid to respond, we're not obligated to respond, and we're unlikely to respond well to comments – like yours here – which suggest a sense of entitlement on the part of the individual asking. You've posted ten questions to the Science Desk in the last week, and five more the week before that — while we find it flattering that you think so highly of us, we're not a robotic search engine that can magically answer every question that pops into your head, and a little patience and courtesy (not to mention an understanding that maybe we can't answer every question) goes a long way. Nil Einne gave you some good advice on your talk page about how to approach other people with requests for help. TenOfAllTrades(talk) 23:13, 17 October 2010 (UTC)[reply]

Elbow braces and tendinitis

I've tried those elbow braces for medial and lateral epicondylitis and they work like a charm. However, I can't understand no matter how much I read why they work. Why does applying pressure to the elbow region heal tendinitis there? Thank you. --Belchman (talk) 20:55, 17 October 2010 (UTC)[reply]

By applying a compressive force just distal to the common flexor and common extensor muscle origins (which are the medial and lateral humeral epicondyles, respectively) the loading forces applied to the muscle group origins is distributed over a greater area and therefore, reduced at the muscle origins. In epicondylitis, usually the initial insult is a strain or overuse injury, and this causes a localised inflammatory response to heal the damage. The constant loading of the musculotendinous origin in the presence of the inflammatory response causes more or less constant re-injury, so it stays painful. Reducing the load applied to the epicondyles, then, has the immediate effect of diminishing the degree of re-injury, so less pain in the short term; and also rests the muscle origins somewhat to provide an environment more conducive to healing, so, hopefuly, less pain in the longer term. Hope that makes sense! Mattopaedia ^{Say G'Day!} 12:28, 19 October 2010 (UTC)[reply]

Thank you. That was an excellent answer. --Belchman (talk) 20:34, 19 October 2010 (UTC)[reply]

You're welcome. Happy to help! Mattopaedia ^{Say G'Day!} 22:05, 19 October 2010 (UTC)[reply]

To what extent are humans adapted to meat-eating?

A debate with my wife: what is the evidence from human teeth and digestive apparatus as to the extent to which we are 'meant' to eat animal protein? —Preceding unsigned comment added by Llocsird (talk • contribs) 21:35, 17 October 2010 (UTC)[reply]

"Meant" isn't a scientific notion, but simple observation says that our teeth and digestive systems handle flesh just fine. Our apely cousins aren't particularly good at hunting (though chimps have been seen to spear small mammals) but will eat flesh when they come across it. Our human ancestors were good hunters; they ate all the mammoths.

The late pop anthropologist Marvin Harris wrote some good books about our species' dietary history. For an extreme modern take, see Paleolithic_diet. PhGustaf (talk) 21:52, 17 October 2010 (UTC)[reply]

The vegetarian rhetoric that humans have evolved to be exclusive vegetarians has pretty much no scientific merit. Without agriculture it'd be very difficult to survive on a vegetarian diet. (That's not to say that with our big brains we couldn't design a better diet than the one we evolved on. For example, one heavy in soy-beans and light on red meat. We don't all live in grass huts in the jungle just because it's what we're "meant" to do!)

There's a good article on the topic on The Straight Dope here. APL (talk) 22:09, 17 October 2010 (UTC)[reply]

To take this from another angle, the risk of tuberculosis is very much increased in those who do not eat meat or meat products.[11] (As I recall, this was known to the ancients, but I disremember the passage at the moment) Wnt (talk) 22:53, 17 October 2010 (UTC)[reply]

That's irrelevant to the question. No one denies that our modern technological society can create a healthy vegetarian diet that's superior to the red meat heavy diet that us westerners (esp. Americans) tend to eat. That's not the question. APL (talk) 00:57, 18 October 2010 (UTC)[reply]

I don't think it's irrelevant - the risk of disease gives a perspective on the quality of nutrition. The contrasting case is gout, which occurs when too much meat is eaten. Wnt (talk) 09:12, 18 October 2010 (UTC)[reply]

Actually we're sort of a marginal case. Neither our teeth nor our digestive system is well adapted to deal with raw meat, but a few hundred thousand years of living with fire have left us pretty well adapted to deal with cooked meat. Looie496 (talk) 00:21, 18 October 2010 (UTC)[reply]

You might want to consider Steak tartare, Carpaccio and Sashimi. --Stephan Schulz (talk) 00:39, 18 October 2010 (UTC)[reply]

It is a bit odd - one of the great theories of human origins involves Homo erectus running for miles to beat off the vultures and crack open the bones left from hyena kills for the marrow. Yet humans seem extraordinarily fragile in regard to rotten food by comparison to many meat-eaters that will cheerfully eat dung, insects, old carcasses and such. I don't understand how humans became so obligatorily finicky. Wnt (talk) 00:54, 18 October 2010 (UTC)[reply]

Back in day, we no have fire! We eat cold carcass and be happy. You tell to kids today, they not believe. APL (talk) 00:57, 18 October 2010 (UTC) [reply]

You had cold carcase? You lucky! 87.81.230.195 (talk) 14:53, 19 October 2010 (UTC)[reply]

Well, we've used fire for cooking for at least tens of thousands of years, maybe hundreds of thousands: we didn't stop evolving. The human gut is not long enough to survive indefinitely on a raw food diet: carnivore or vegetarian, we need fire to cook it. I'd like to be able to recommend The Artificial Ape, which I'd hoped would be a nice summary of the what we know so far, but I'm only in the first few chapters and I'm already intensely irritated with some of his reasoning, some of his unsourced claims, and a lot of bombast: perhaps it will calm down later and undo some of that, and then I'll feel able to recommend it. 109.155.37.180 (talk) 01:07, 18 October 2010 (UTC)[reply]

Well, we cannot survive indefinitely on any kind of food, although I'll sure try. But I'm fairly certain that you can devise an uncooked diet that will keep you alive for a long long time - start with milk, bananas, and raw eggs. But what is true is that many of our most important staple foods require cooking or become much more nutritionally valuable by cooking - potatoes, rice, grains for example. --Stephan Schulz (talk) 16:31, 18 October 2010 (UTC)[reply]

Starting with milk sounds like a bad idea, unless you know the people you target are lactose tolerant which many people are not Nil Einne (talk) 20:02, 18 October 2010 (UTC)[reply]

Medical studies that I've read repeatedly state that most people are lactose tolerant. When asked, they claim to be lactose intolerant because they are afraid that milk will make them fart. Another issue is the coldness of milk. Many cultures do not drink cold liquids, so they are cold intolerant, not lactose intolerant. All in all, it is more mental than physical - which tends to be the case with a lot of human-related issues. -- kainaw ™ 20:10, 18 October 2010 (UTC)[reply]

Is that most westerners? Or most people? APL (talk) 01:26, 19 October 2010 (UTC)[reply]

Most people. The studies that I have to study are often from China, India, and Africa - much less often a study on "westerners". The problem is differentiating between "I don't like milk" and "lactose intolerance". A good measure is a hydrogen breath test. It measures true intolerance. Most people are not intolerant, but they cannot consume milk for various reasons. Worldwide, the predominant reason is that milk is served cold and the people get stomach cramps when trying to consume cold liquids. -- kainaw ™ 12:00, 19 October 2010 (UTC)[reply]

There was an episode on BBC Horizon called " Did Cooking Make Us Human?" that deals with this topic.[12] It basically said that cooking foods and eating animals were crucial for early human survival and our subsequent evolution. In fact in a recent issue of Scientific America there has been evidence of early humans butchering and eating animal about 3.4 million years ago![13] Cooking came later in the game, but according to BBC Horizon that could have been a few hundred of thousands of years ago too. -- Sjschen (talk) 18:19, 18 October 2010 (UTC)[reply]

Wildlife ID - does this sound like a slime mold?

A few days ago I spotted a Plantago plant (I think Plantago lanceolata) in Herefordshire in the UK, which had an an unusual growth on one of its leaves. There was a white growth, which looked like snow, that was growing around the leaf, covering around 4cm of the leaf and was several mm thick. It was relatively hard, but when I scratched it with a plant stem some material was removed and it was granular in appearance. The parts of the leaf that where still visible showed no signs of damage (like discolouration or a lack of turgidity). I'm curious as to whether anyone could suggest what it might possibly have been? The only thing I could think it might be was a slime mold (mainly because they're a bit strange!), but I'm a bit confused as to how such a relatively large structure could grow, without damaging the leaf. I'm almost certain they couldn't have been eggs of any form as it appeared to grow very slightly over several days. (Sorry for the lack of photo, which I know would help tremendously - I was enjoying 10 days without electronics). Thanks Smartse (talk) 21:43, 17 October 2010 (UTC)[reply]

Many forms of plant pathogens could also result in the symptoms you describe, including the growth. See e.g. Plant_pathology#Fungi. From what I know, most slime molds are detritivores , or eat soil-dwelling microorganisms. In the wild, I think they tend to be found more on dead wood or in leaf litter, rather than on a living plant you describe. So, in short, my guess is no, not a slime mold. --SemanticMantis (talk) 16:05, 21 October 2010 (UTC)[reply]