Wikipedia:Reference desk/Archives/Science/2008 March 17

= March 17 =

Brushing teeth with bleach?
--S.dedalus (talk) 02:39, 17 March 2008 (UTC)


 * I am not seeking medical advice. H YENASTE 02:48, 17 March 2008 (UTC)
 * Good because you're not going to get it. This is a stupid question. Theresa Knott | The otter sank 11:07, 17 March 2008 (UTC)


 * What does it say on the label on your bleach bottle? Read the part where it states the health risks.  Why expect someone here to know more than the manufacturers who had lawyers work up the warning label? --  k a i n a w &trade; 02:38, 17 March 2008 (UTC)


 * It may be worth pointing out that the questioner seems to have been misled by the notion of "bleaching" teeth. When teeth are "bleached", it is done with specific preparations designed to whiten teeth, none of which contain household bleach (sodium hypochlorite). You don't bleach teeth with bleach. - Nunh-huh 14:21, 17 March 2008 (UTC)

what is the plant in this picture?


I was walking in the park with my boyfriend today and we could not identify the round bushy plants. They are in the background of this pic...Are they called pampa grass or somthing?W-i-k-i-l-o-v-e-r-1-7 (talk) 00:58, 17 March 2008 (UTC)
 * What part of the world is this in? -GTBacchus(talk) 03:23, 17 March 2008 (UTC)

Pacifica, California. I this Pampas Grass?W-i-k-i-l-o-v-e-r-1-7 (talk) 03:40, 17 March 2008 (UTC)
 * Hi, there's an illustration here of purple needlegrass or it could be a kind of para grass in California. It looks like the lower green grass has grown through and up around the dieback. Julia Rossi (talk) 05:44, 17 March 2008 (UTC) (Sorry, not since it's blue-green and belongs to your main plant.)
 * I think you are right, that this is pampas grass (not a native plant, but common in that area). You are seeing this years fresh green growth coming up through the broken and tangled dry remains of last years leaves and stems. --169.230.94.28 (talk) 16:23, 17 March 2008 (UTC)

Did the Big Bang go bang
My understanding of the BB is that before it there was nothing. A split second after the BB was hydrogen and maybe some hellium. And that the "Big Bang" was an explosion. Like they said on the History chanel, "the Universe" exploded into existence. So I mentioned this to a friend and said that the Big Bang was an explosion. And that before that there was nothing. He said I was wrong on both accounts. I all but called him a morron. He is not an ID. He is saying that the BB was not an explosion. My Q: If it was not an explosion then what was it? Q: what was it that exploded? What was there before the BB? thanks cris —Preceding unsigned comment added by Loach (talk • contribs) 01:11, 17 March 2008 (UTC)


 * The Big Bang was an explosion, in the sense that it was a rapid expansion of energy and matter. The tricky bit about it is that it wasn't just a bunch of compacted stuff exploding into the surrounding space, it was an explosion of the space itself. And, at the same time that space came into being, so did time, so it doesn't really make sense to ask "what came before the Big Bang", since there was no before - a similar question in spatial co-ordinates would be "what's North of the North Pole?" Take a look at Big Bang and Timeline of the Big Bang for more details. Confusing Manifestation (Say hi!) 02:55, 17 March 2008 (UTC)

Thank you. That is more or less what I thought. Again, thank you for the help. —Preceding unsigned comment added by 68.209.69.103 (talk) 03:20, 17 March 2008 (UTC)


 * I could have been your friend. The terminology is very confusing. "Big bang cosmology" is a description of the evolution of the universe over the last 13.7 billion years. It's not a description of how the universe started. The model has a mathematical singularity called "the big bang singularity" or just "the big bang", which you can think of as a limiting state of infinite density, but nobody takes it seriously; it's seen as a sign that the model breaks down there. Among people who speculate about what should replace the singularity, the most popular models involve a universe with no particular beginning of time (that is, there's nothing inherent in the models that suggests a beginning of time, in contrast to the big bang model, which has a singularity at a finite time in the past). See also Age of the universe. As to whether the expansion of the universe should be called an explosion, that's a matter of terminology, but I tend to think that it doesn't fit the dictionary definition of an explosion very well. For one thing, one normally thinks of an explosion as expanding outward into the surrounding space, and there's no space surrounding the universe. It's homogeneous. Note that if it was an explosion then the explosion is still going on; there's no transition point at which it stopped exploding and started just expanding. -- BenRG (talk) 12:05, 17 March 2008 (UTC)


 * A fun little bit of history -- the "Big Bang" was a term used first by Prof. Sir Fred Hoyle, one of the Big Bang's most outspoken critics. He had used the term disparagingly, and as a contrast to his "Steady State" model, but (assumedly to his chagrin) the phrase caught on first among the general public, and eventually in the scientific community.  Bill Bryson's excellent book "A Short History of Nearly Everything" tells the tale entertainingly.  Also see the obituary at .Vance.mcpherson (talk) 19:53, 17 March 2008 (UTC)

eggs
Do all eggs contain all of the amino acids, i.e., if forced to live in a survival situation with nothing but eggs how long could you survive with no other food? —Preceding unsigned comment added by 71.100.174.10 (talk) 01:55, 17 March 2008 (UTC)


 * Assuming you are referring to chicken eggs, they contain very little vitamin C. Without vitamin C, scurvy is very likely to occur. --  k a i n a w &trade; 02:36, 17 March 2008 (UTC)


 * Which is true, and pertinent to the second part of the question. As to the first part, yes, eggs contain all of the essential amino acids, which is the reason they are considered a "high quality" source of protein. But as Kainaw points out, the essential amino acids alone aren't enough to support health; there are other essential nutrients that are not amino acids. (Another problem is that eggs contain avidin, so a diet consisting entirely of eggs is likely to cause biotin deficiency. - Nunh-huh 03:02, 17 March 2008 (UTC)


 * As a followup question what basic items contain all of the nutients essential for indefinite survival? —Preceding unsigned comment added by 71.100.174.10 (talk) 04:56, 17 March 2008 (UTC)


 * I asked a question before about human milk, which, after all, is designed to provide for all human nutritional needs, at least for a baby. However, the nutritional label on regular cow's milk seems to indicate it is lacking in many nutrients we need.  I forget if this discrepancy was ever explained. StuRat (talk) 05:57, 17 March 2008 (UTC)


 * (Not sarcasm here.) And that's why it's cow's milk and not us-milk, and is made up with supplements for human infants. There's a nice section about comparative milks here. Julia Rossi (talk) 06:06, 17 March 2008 (UTC)


 * But human milk doesn't contain all the nutrients we need, like iron and folic acid: . So how do babies survive on it ? StuRat (talk) 17:29, 17 March 2008 (UTC)


 * Because they're babies and have different nutritional needs to us. That's why, apart from the convenience factor, they have to be weaned as they grow up and start developing different nutritional needs. And why you can't feed a tiny baby puréed adult food instead of milk. Skittle (talk) 13:19, 18 March 2008 (UTC)


 * Babies do have different nutritional requirements, yes, like needing more fat and cholesterol to support rapid growth. However, they certainly must require iron for growth, as well.  Don't babies have hemoglobin in their blood ? StuRat (talk) 14:30, 18 March 2008 (UTC)

It sounds like you saying that human milk and supplemented cow's milk provide complete nutrition for indefinite survival. What I am really looking for are combinations of other foods that one might search for and find in a survival situation like egg of all types for protein and pine needles for Vit C. I'm sure there must be lots of combinations so I am trying to find out what they are. Is there a chart somewhere perhaps that shows all of the required essentals with overlays of the portions provided by various foods? —Preceding unsigned comment added by 71.100.174.10 (talk) 07:43, 17 March 2008 (UTC)


 * Adventurers seem to know what food to take that doesn't weigh much and keeps them going for days (eg beef jerky, dried fruits, nuts and chocolate), but I don't know what that would be listed under. About milk, my take is that it isn't the complete food. I looked at space food but there's no information about nutrition just mechanics. Julia Rossi (talk) 08:53, 17 March 2008 (UTC)


 * Space food has some interesting information but I'm not looking for food which is pre-prepared but rather items which one might look for in the great outdoors, i.e., jungle, coastline, desert, etc. I'm not necessarily looking for foods you can take with you but rather foods that you can find. —Preceding unsigned comment added by 71.100.174.10 (talk) 15:35, 17 March 2008 (UTC)


 * You may be interested in some of the references of the Survival skills article. What food sources you might encounter in a wilderness would of course depend entirely on what biotope you are in – looking for mussels, for example, would be a great idea on the coast but less useful in an inland desert... So where exactly are you planning to get stranded? Also note that you can survive for weeks without any food at all, and for months or years on an incomplete diet. Are we talking about a permanent situation here, or a would crawling back towards inhabited areas be an option? --169.230.94.28 (talk) 16:13, 17 March 2008 (UTC)
 * In my youth when I ran away from home my inability to find a hamburger, French fries and a soda usually brought me to my senses and led me to the nearest pavement an on to the nearest fast food store. Now that I am older I'm curious just how long I can go out there somewhere nobody else is without need for finding pavement and inevitably French fried onion rings. —Preceding unsigned comment added by 71.100.171.236 (talk) 22:32, 17 March 2008 (UTC)

If you supplemented your eggs with fruits and vegetables I think you'd do pretty well. If you knew your edible plants better than how to steal eggs (you might decimate the local population rather fast depending on where you are eating only eggs), you could also do well combining grains with beans or nuts for your protein. Variety would be the key, some meat, some fruit, etc., since there's no one food you can healthily live on forever. &mdash; Laura Scudder &#9742; 16:31, 17 March 2008 (UTC)

Sodium-potassium pumps
What percentage of the ATP that is used in the body is used by the brain to run the sodium potassium pumps? Schmultz (talk) 03:05, 17 March 2008 (UTC)schmultz
 * 25%-30%, but don't reference me in your thesis. Mac Davis (talk) 04:46, 17 March 2008 (UTC)

Phosphodiester bonds
I want to know whether a molecule of water is removed when forming a phosphodiester bond between 2 DNA neucleotides. —Preceding unsigned comment added by 124.43.61.81 (talk) 06:42, 17 March 2008 (UTC)
 * Yes. Someguy1221 (talk) 09:24, 17 March 2008 (UTC)


 * See condensation reaction.  Wisdom89  ( T |undefined /  C ) 19:03, 17 March 2008 (UTC)

infrared raman spectroscopy
can infrared raman spectroscopy be used to detect bones in in vivo detection Neel shah556 (talk) 08:22, 17 March 2008 (UTC)


 * If the bones are covered by flesh, no. Infrared raman spec is used mostly on thin tissue samples or single cells. In these samples it can detect differences in the concentrations of proteins, lipids, carbohydrates and nucleic acids.--Shniken1 (talk) 11:11, 17 March 2008 (UTC)


 * Good answer ("that's using the old noodle"). :-) StuRat (talk) 14:48, 18 March 2008 (UTC)

Minimum entropy
Can whatever proceeded the Big Bang be defined as the state of minimum entropy?


 * There is no accepted physical theory on what preceded the big bang. In fact, accepted physics only deals with what happened after the very moment of the big bang. So there's nothing you can say about it. Someguy1221 (talk) 09:30, 17 March 2008 (UTC)


 * It is reasonable to say that some point in the early or very early universe there was a point of least entropy, and that entropy has increased since then, giving a direction to the cosmological arrow of time. The problem lies in trying to pin down just when this point of least entropy was. One big difficulty is that we have no agreed model for the physics of the very early universe (up to the end of the inflationary epoch) so we can't be sure that the second law of thermodynamics even applied then. One theory is that inflation itself drove entropy down, so that the point of least entropy is at the end of inflation, and the universe has been climbing out of this entropy "hole" ever since. Gandalf61 (talk) 12:15, 17 March 2008 (UTC)

swing??
why can't bernoulli's theorem be used to explain swing in cricket balls? --scoobydoo (talk) 14:19, 17 March 2008 (UTC)

because cricket is not a series of tubes? —Preceding unsigned comment added by 79.122.42.52 (talk) 14:59, 17 March 2008 (UTC)


 * I've read through the article and I suppose it might involve Bernoulli's Principle, but since I'm American half the words are complete Greek to me. The article doesn't really explain what swing does, can someone fix that? 206.252.74.48 (talk) 19:05, 17 March 2008 (UTC)


 * The Swing bowling article might help, but it is still full of cricket jargon. Perhaps the best explanation for american ears is to think of it like pitching a curveball, but using a different principle to get the ball to curve. Astronaut (talk) 03:36, 18 March 2008 (UTC)


 * Most ball sports players, can use Bernoulli's Theorem to cause the ball to curve in flight. I've seen it in football, golf, tennis, table tennis, baseball.  However, I think Bernoulli's Theorem assumes the surface is of constant roughness.  In cricket, bowlers will polish one side of the ball (by polishing it on their trousers), and occasionally cheat by roughening the other side (by stepping on the ball with their spiked shoes or scratching the surface with coins or dirt).  Having one smooth side and one rough side affects the airflow around the ball and causes it to curve in flight - towards the rough side (I think :-)) where there is more aerodynamic drag.  If the bowler has also put some spin on the ball, the overall effect can be very complicated.  Astronaut (talk) 03:36, 18 March 2008 (UTC)


 * See also the related Magnus effect. -- Coneslayer (talk) 22:06, 19 March 2008 (UTC)

temp & fire
does temperature & fire have any relation? i mean, can i put out the fire of a burning body by cooling it?--scoobydoo (talk) 14:23, 17 March 2008 (UTC)


 * You might be able to - for instance if you manage to freeze it.


 * Also some things just won't burn below a certain temperature.87.102.13.144 (talk) 14:56, 17 March 2008 (UTC)

See our article on fire triangle. Fires do need heat. Rapidly cooling a fire (by adding lots of water for example) does put it out. Theresa Knott | The otter sank 15:25, 17 March 2008 (UTC)


 * NASA has a page here that shows how to snuff a candle by drawing the heat away from the wick with a coil of bare copper wire. --Milkbreath (talk) 16:47, 17 March 2008 (UTC)


 * There are basically three ways to extinguish a fire: deprive it of heat, fuel, or oxygen. Spraying water on a fire removes heat because the water absorbs heat when it is vaporized to form steam.  Since water is inexpensive and readily available, this makes a good choice for most fires.  It's not a good choice for some fires, like electrical fires (because water conducts electricity and could electrocute the firefighters) and oil fires (because water can splatter burning oil).  In such cases they normally try to deprive the fire of oxygen by using halon or foam, or just wait until it burns itself out by using up the available fuel supply. StuRat (talk) 14:42, 18 March 2008 (UTC)


 * You can actually put out fires by causing an explosion nearby. The more you know... sho  y  03:53, 20 March 2008 (UTC)

Speed of ...
Say you have a rigid object, such as a meter long titanium pole. When you pull one end, the other end presumably doesn't move instantly, because the force would have to move faster than the speed of light. It must be determined by the flexibility between the bonds of the titanium atoms/molecules. So ignoring the impracticality of its weight and size, if you were to pull a light-year, or some similar length, long titanium pole, the other end wouldn't notice it's been pulled until all the bonds are at their maximum pulling length? At that point, it still can't be instant if it's pulled further? Could anyone elaborate on what goes on? -- MacAddct &#xF8FF; 1984 (talk &#149; contribs) 15:16, 17 March 2008 (UTC)


 * I'm not sure what you are asking but yes, it is impossible to pull all of it instantaniously. The rod will deform elastically and the pull will travel down it at the speed of sound in that material. (much slower than the speed of light). Theresa Knott | The otter sank 15:28, 17 March 2008 (UTC)


 * This is a Reference Desk Frequently-Asked Question but I think you've already sussed-out the answer: What we consider to be the "structural strength" of solid materials is actually the electromagnetic interaction of the electron shells of the constituent atoms. And these electromagnetic interactions can never propagate faster than the speed of light. So if you pull or push on that light-year-long titanium rod, a compression or expansion wave propagates through the material. It certainly doesn't go faster than the speed of light and probably only travels at the speed of sound in that material.


 * Atlant (talk) 15:31, 17 March 2008 (UTC)


 * Thanks! Yeah, that's about what I was thinking. It's hard to think in terms of familiar objects moving in ways we're not familiar with.


 * As for it being FAQ, is there an FAQ (official or unofficial) for the Reference Desk? If not, there really should be one started... -- MacAddct &#xF8FF; 1984 (talk &#149; contribs) 15:53, 17 March 2008 (UTC)


 * There is a FAQ page, at Reference_desk/FAQ. It is embryonic and underused, because it is hidden. We should link to it from the main RD page, and maybe mention it in the Before asking a question/Search first section at the top of each RD page. --169.230.94.28 (talk) 19:04, 17 March 2008 (UTC)


 * So what happens if you move one end faster than the speed of sound ? StuRat (talk) 17:36, 17 March 2008 (UTC)


 * You'd be breaking the rod. By definition you would be moving the atoms faster than they could convey that movement on to the atoms next to it; the rod wouldn't be structurally stable if you could do that, by definition. Remember it's the speed of sound in that material, not the speed of sound in air, which is normally what we think the speed of sound as being. --Captain Ref Desk (talk) 18:08, 17 March 2008 (UTC)
 * Or, if you are moving in a compressive direction, and buckling doesn't occur, you may create a shock wave. --169.230.94.28 (talk) 19:04, 17 March 2008 (UTC)
 * It's not speed that would break or buckle the rod, but acceleration 196.2.113.148 (talk) 22:07, 17 March 2008 (UTC)

Diabetes
I've been told that in the disease of Diabetes damage to the body is done by excessive amounts of either sugar or insulin molecules. Exactly what type of damage is done by excess amounts of either molecule besides oppressing the production/utilization of the other molecule that would cause the loss of toes? Is it damage to cell chemistry or structure, and if so of what does the damage consist? —Preceding unsigned comment added by 71.100.174.10 (talk) 15:47, 17 March 2008 (UTC)


 * Wikipedia has a very detailed article on diabetes, signs and symptoms, the different types, etc... -- MacAddct &#xF8FF; 1984 (talk &#149; contribs) 15:56, 17 March 2008 (UTC)


 * If you're losing toes, you should go see the doctor. -- MacAddct &#xF8FF; 1984 (talk &#149; contribs) 15:58, 17 March 2008 (UTC)
 * LOL... I'm hoping to learn what the sugar and the insulin do to the body that causes reports to be written of poeple with Diabeties to loose toes. Mine remain quit tasty, thanks, according to the wife. —Preceding unsigned comment added by 71.100.171.236 (talk) 21:40, 17 March 2008 (UTC)


 * Nothing in the post suggests that the poster is losing toes.
 * More specifically this is probably the section of the article you need. AlmostReadytoFly (talk) 16:52, 17 March 2008 (UTC)
 * this is much more what I'm looking for. Thanks.

It brings tears to my eyes...
...to waste part of an onion, but are the green sprouts in the center edible ? That is, should I make the best of them or make compost of them ? StuRat (talk) 18:07, 17 March 2008 (UTC)


 * They are edible, but you are only getting them as your onions are starting to grow. Try keeping your onions in a dark cool place, if in a hot country the fridge will do. This will stop the central green bit appearing. Taste wise the green bit will be slightly more tough than the cooked down flesh, more similar to a spring onion. I would not use it in a Burre Blanc sauce but it would be fine in a stir fry or stew. GameKeeper (talk) 19:23, 17 March 2008 (UTC)


 * Thx. StuRat (talk) 20:06, 17 March 2008 (UTC)


 * 1138? 206.252.74.48 (talk) 16:01, 18 March 2008 (UTC)

1-Octen-3-ol CAS numbers?
I'm trying to track down the CAS numbers for 1-octen-3-ol. The best I could find is this page from a book about coffee. It lists the numbers [3391-86-4], (&plusmn;) [50999-79-6], (R)-(-) [3687-48-7], (S)-(+) [24587-53-9]. The latter two clearly refer to the two enantiomers. My question is: what's the difference between 3391-86-4 and 50999-79-6? Both appear to refer to a mixture of the two enantiomers. Thanks, AxelBoldt (talk) 18:43, 17 March 2008 (UTC)


 * [3391-86-4] clearly states "matsutake alcohol FEMA 2805" almost certainly "Flavor and Extract Manufacturers Association".


 * The most probable explanation is that the natural product 'matsutake alcohol' was known before it was recognised to be indentical to 1-octen-3-ol, hence the different numbers.


 * The simplest way if possible would be to examine the papers referenced by [3391-86-4] and see exactly what they describe.87.102.13.144 (talk) 19:32, 17 March 2008 (UTC)


 * Also [3391-86-4] might refer to a naturally obtained product - if in the future this product is shown to contain other components then the distinction will be useful (for example conside oil of almond which is almost all benzaldhehyde - but not 100%)
 * Take a look at the papers cited for both from chemical abstracts - this might give you a clue as to what's going on eg does the use of one of the numbers cease after a certain date, or is the term 'matsutake' specific to certain countries ?87.102.13.144 (talk) 19:40, 17 March 2008 (UTC)


 * According to CAS, [50999-79-6] is a deleted CAS number and [3391-86-4] should be used. -- Ed (Edgar181) 19:44, 17 March 2008 (UTC)

Magical self cleaning wound
Yesterday I cut myself in my finger whilst outside. It had some dirt in it so I attempted to clean it to the best of my ability. However some small about of debris was still stuck inside. After a while I stopped trying to get the debris out, thinking it would most likely do more harm than good to go out of my way to pick out the last bit of dirt. Come next morning my wound was magically clean. And when I say clean I mean, perfect pink/reddish skin with not a hint of dirt. I'm wondering, where did this dirt go? Is there some mechanism by which wounds are able to expel small amounts of debris? Did it just fall out whilst I was sleeping even though I couldn't get it out myself? PvT (talk) 18:58, 17 March 2008 (UTC)


 * Blood would be the obvious agent to pour out of a wound and cleanse it. I've also noticed a clear fluid flow out of wounds not deep enough to bleed.  I suspect that this is the blood plasma without the red blood cells, which need a larger opening to escape.  Pus can also flow out, but only after the wound becomes infected.  StuRat (talk) 19:13, 17 March 2008 (UTC)

Well the skin literally grows from inside to out - so it's unlikely to trap any dirt.. Once formed the new skin layer will be drier than a wound making it less sticky - and so any remaining dirt just fell off. Probably.87.102.13.144 (talk) 19:15, 17 March 2008 (UTC)

There is also the possibility that while you were asleep your unconcious mind went to work scraping the wound against the bed sheets or instructing other parts of your body to scratch or rub the wound. Sleep study video reveals all sorts of directed movements as if we were actually or part awake.


 * I wouldn't be so sure wounds are self-cleaning. When I was a child, I managed to stab myself in the hand with a newly sharpened pencil.  Decades later, I still have a small grey dot under the skin.  Astronaut (talk) 02:47, 18 March 2008 (UTC)


 * And I have a 20 year old splinter that hasn't managed to work it's way out, yet. StuRat (talk) 04:41, 18 March 2008 (UTC)


 * I too have a mark from a pencil stab (a "friend" did this to me in primary school). I think these are different from cuts as they are deep puncture wounds. Also, the graphite is organically neutral meaning that it won't be attacked by the immune system. I once had a thorn stuck in a deep cut, and it became an infected boil, and the thorn was eventually ejected along with puss. -- Q Chris (talk) 10:10, 18 March 2008 (UTC)


 * In my case I believe the wooden splinter eventually dissolved, leaving the dark brown wood stain which once coated the splinter behind as a type of tattoo. StuRat (talk) 14:19, 18 March 2008 (UTC)
 * As far as I know White blood cells do this trick, if that dosen't happen right away some white cells will die trying and form pus, which should do the trick then. As for some particles sometimes remaining in the body - I guess this is because new skin forms before immune system has managed to clean the wound, and even then sometimes stuff grown into the body is eventualy pushed out, but probably this happens to larger (or otherwise "more dangerous") stuff than dirt. Xil ...  sist!  23:45, 20 March 2008 (UTC)

Searching for massively-multiplayer synonyms in PubMed
So "tight junction protein 1" has a variety of names; how am I supposed to search effectively in PubMed? Is there some way of referring to this gene/protein in such a way that all synonyms are searched for at once?


 * I might be wrong, but a little further down on that page it has all of the names in a list box ("Search for TJP1"). Hold down shift and you can select all of them at once. Change the boolean term to OR so that you get publications with any of those names in it (AND would get publications that contain each and every one of them). Hit search. Many results abound. --Captain Ref Desk (talk) 20:25, 17 March 2008 (UTC)


 * Have you ever worked with the MeSH function?
 * Change the drop down to "MeSH" and search for, say, tjp 1. The result shows zonula occludens-2 protein, and it the page lists the synonyms.  On the same line of the substance name, all the way to the right, click on "Link", then on "Pubmed".  Hopefully this will give you good results. 128.163.116.64 (talk) 22:18, 17 March 2008 (UTC)

Chem Acid Stoichimetry problem
Suppose I was given Ba(OH)2 at 0.5 M/L and was asked to find it's pOH. Since it's diprotic, I have to multiply the concentration by 2 right? If so, why do I multiply the concentration by 2? Why not the number of moles?

It will dissociate into Ba + 2OH right? 99.240.177.206 (talk) 21:04, 17 March 2008 (UTC)


 * Yes, Ba(OH)2 will dissociate into Ba2+ and two OH- (note charges). It's not really diprotic, as it has two hydroxyls, not two protons (diprotic refers to acids, not bases). The reason you multiply by two is that each mole of Ba(OH)2 contains two moles of OH-, so in a sense, 2 is the number of moles. BTW, this analysis only holds if the barium hydroxide is completely dissolved and completely dissociated. If it's a weak base it may stick around as dissolved Ba(OH)2 or possibly Ba(OH)+ (Sorry, I don't know the pKas of Ba(OH)2, so I can't give you a definitive answer.) Also, I don't think the solubilities work out - the barium hydroxide article lists the solubility as ~60 g/L (for the octahydrate), whereas a 0.5 M solution would be ~150 g/L (for the octahydrate). Lastly be aware that the capitol M already means moles per liter (molar). You don't have to divide through by liters again, unless you mean moles per liter per liter. -- 128.104.112.85 (talk) 21:46, 17 March 2008 (UTC)
 * If we're going to be pedantic about terminology, then it's the Kb, not the Ka.
 * Now, you have a molarity of .5M. Let's set up the first equation. Barium Hydroxide has a Kb of 104.71. Assuming that's for the reaction Ba(OH)2 --> Ba+2 + 2OH-, we have the following:
 * 104.71=[Ba+2][OH-]^2/[BA(OH)2]
 * 104.71=(x)(2x)^2/(.5-x) (where x is the number of moles/L disassociated)
 * 104.71=4x^3/(.5-x)
 * x=.4954
 * We really want 2x, since we get 2 mol OH for every mol Ba(OH)2
 * 2x=.9907
 * [OH-]=.9907
 * pOH=.00405
 * Odds are, this is completely wrong. --uǝʌǝsʎʇɹoɟʇs (st47) 21:55, 21 March 2008 (UTC)

Part of the USS Pampanito's hull
The USS Pampanito is the submarine pictured in this photo. Is there a term for the black part of its hull that tapers from the bow? Or is it still the hull? -- Broken Sphere Msg me 21:08, 17 March 2008 (UTC)
 * If you mean the part that bulges around the waterline, I'd say tapers to. That said, it's certainly part of the hull -- or at least the light hull.  On similar-era U-boats, those structures were "saddle tanks" -- auxiliary ballast tanks.  Such tanks could also be designed to carry fuel, but the Germans left their diesel tanks inside the pressure hull to improve depth charge survivability. &mdash; Lomn 21:23, 17 March 2008 (UTC)
 * Whaddaya know? Saddle tank (submarine). &mdash; Lomn 21:27, 17 March 2008 (UTC)

Paraffin/aluminium foil
Years ago at a ski-lodge as after-dinner entertainment one of the guests carried out a trick involving a bit of chemistry, and I wonder whether anyone here knows how it was done. A piece of foil - the type found in some cigarette packs - had something done to it using paraffin/kerosene. The foil was then crumpled into a tight ball and placed in the palm of the hand. Within a few seconds it became too hot to hold. How was it done? —Preceding unsigned comment added by 196.2.113.148 (talk) 21:56, 17 March 2008 (UTC)
 * Probably caustic soda......Rotational (talk) 16:18, 18 March 2008 (UTC)