Wikipedia:Reference desk/Archives/Science/2006 August 11

How to produce TiCL4 in industry
please tell me how to produce TiCl4 from Ilmenite ore in industry. why the producer usually produce TiCl4 from Rutile without Ilmenite. AND could you tell me how to separate Vanadium from crude TiCl4


 * Is this homework by any chance? Why not try looking at the pages I have linked for you and try to work it out for yourself?--Light current 03:02, 11 August 2006 (UTC)


 * How do you get Vanadium from TiCl4? Isopropyl 13:57, 11 August 2006 (UTC)


 * You dont. Why dont you look at the pages Ive linked! 8-)--Light current 14:03, 11 August 2006 (UTC)
 * Alchemy. Tito xd (?!?) 09:44, 12 August 2006 (UTC)

IMAGE TRANSFER CONSTANT.
I Wanna know what is


 * You wanna??? Try rephrasing the question--Light current 04:42, 11 August 2006 (UTC)


 * I think they want to know what "image transfer constant" means. I can't help, except to say it apparently has something to do with electronics .  --Allen 04:51, 11 August 2006 (UTC)


 * Doesnt mean anything in my electronics knowledge!--Light current 05:01, 11 August 2006 (UTC)

Passengers boarding bridges.
tell me more about passengers boarding bridges, technology used in it. and also manufacturers —Preceding unsigned comment added by 59.144.44.56 (talk • contribs)


 * Tell you what? TRy rephrasing--Light current 05:45, 11 August 2006 (UTC)


 * Do you mean a jetway? Take a look at the article and its links.--Shantavira 07:13, 11 August 2006 (UTC)

solution of liquids inside vessels
A niece, who is very concerned about health issues, recently told me that she was avoiding buying mineral water in plastic bottles, because "the plastic gets dissolved" and was instead using only glass bottles.

This set me thinking about the whole issue of the solubility of vessels. I remember from my physics lessons in school that all vessels are dissolved to a certain extent by the contained liquid and also, though it may not be strictly relevant, that research in West Africa, where I worked for many years, indicated that when the local people stopped using the traditional iron cauldrons for their stews and went for more modern cooking appliances, they lost out on iron in their diet (derived from the cauldron).

I realize that the issues are extremely complex because they depend on: the nature of the vessel, whether wood, pottery, glass, platic; what the liquid is...anything from water, whiskey, sulphuric acid; maybe the environmental conditions such as temperature.

Even with water the nature of acidity and impurities in the water would presumably have an effect.

So to keep in simple, I am requesting as to whether anybody has statistical data on the solubility of different types of vessels in water (perhaps of different qualities) contained in the vessels. Are these rates to be considered signficant in any case in terms of ingestion by the drinker or are they, as one scientist told me over the phone last night, just of laboratory interest like the phenomenon that the glass in your window pane is gradually sliding downwards.85.12.64.148 08:50, 11 August 2006 (UTC)F.D. O'Reilly −Ihana enterprises


 * I might not be a full fledged scientist but I'd think that the plastic in most bottles will not dissolve, in any substantial amount, into the liquid it contains. Even if it did dissolve into the liquid it contained, you should remember that little children swallow plastic bits from their toys all the time, it simply passes through their system. PvT 09:27, 11 August 2006 (UTC)


 * Pharmaceutical companies spend quite a lot of time worrying about 'partition coefficients' - how much a given chemical prefers oily (hydrophobic) liquids to water. You can search for 'log P' or 'log D' values for compounds you're interested in. I'll bet that most plastics (or specifically the monomers) in water bottles have pretty high log P values (i.e. they much prefer oily solvents). They're unlikely to leach into water in significant amounts. Of course, I could be wrong. Ignoramibus 05:44, 16 August 2006 (UTC)

Who cares if plastic got into the water? Why does she care? Before you do anything, she has to tell you why it matters =D. Oh yeah, and glass doesn't flow =D. People just got that idea because the way they used to make windows would make the edges "bulge". So people see old windows, see that the bottom seems to be "thicker" and assume water is liquid. Cheers --mboverload @ 09:45, 11 August 2006 (UTC)


 * I ve learned something today: solid glass doesnt flow. But rock and mountains do (v slowly)--Light current 14:15, 11 August 2006 (UTC)

Yeh the sliding glass phenonemon is a myth that derives from the fact that early panes of glass are thicker at one end, because the technology wasn't accurate enough to produce flat glass, not because they changed shape. I would consider the effects of using iron pots, irrelavent to this case, as plastic and iron are extremely different physically and chemically. The only thing I have heard about plastic bottles is that the free radicals on the end of the polymerised chains cause carbondioxide to be absorded out of the water, and connect to then ends of the chains, but all that does is decrease fizziness. Anyway plastic is made of carbon and hydrogen neither of which are harmful (infact they are essential for survival) so I dont see any problems with ingesting microscopic amounts anyway. Philc TECI 12:00, 11 August 2006 (UTC)


 * It's quite absurd to say that everything made out of carbon and hydrogen is completely safe. Thousands of hydrocarbons are toxic, including some in plastic containers. StuRat 00:49, 12 August 2006 (UTC)


 * There should be little concern that plastic will dissolve in water, or anything else you want to drink. But there is legitimate concern about plasticizers such as phthalates, which are non-polymeric chemical compounds added to the plastics to improve their physical properties.  There are controversies surrounding the health effects of these compounds. --Ed (Edgar181) 12:49, 11 August 2006 (UTC)

It sounds to me as if your niece has succumbed to the plastic-dioxin hoax. --Ginkgo100 talk · contribs · e@ 17:37, 11 August 2006 (UTC)


 * Plastics most definitely do give off chemicals into the liquid they contain. This seems to be particularly true if the liquid is acidic.  Ever notice a total lack of plastic pickle jars ?  There is a reason for this.  Spaghetti sauce also usually comes in glass, as plastic bottles, especially soft ones, tend to absorb tomato color and odor, just as the sauce absorbs a plastic taste and odor.  Soft plastics, like those used in two liter pop bottles, also seem worse than hard plastics.  Time is another important factor.  If you wait long enough, anything in a plastic bottle will acquire an unpleasant plastic taste.  This is why water in plastic bottles has an expiration date.  Temperature is also important.  Keeping plastics cool would lower the speed at which the diffusion of chemicals into the contents takes place.  However, avoid freezing, as the stress put on the bottle by the contents expanding actually increases diffusion of chemicals from the plastic.  To be completely safe, avoid plastic wherever possible.  Now, if anyone doubts what I've said here, get a plastic pop bottle, pop in a metal can, and pop in a glass bottle; store each under identical conditions for 10 years, then compare the three.  The plastic bottle version will be completely flat and disgusting, while the pop in the can will be better (perhaps with a metallic taste) and the pop in the glass bottle will be exactly the same as when new. StuRat 19:53, 12 August 2006 (UTC)


 * You say that you have to avoid plastics to be safe, but you fail to give any reason to actually do so.    --mboverload @  00:49, 12 August 2006 (UTC)


 * Because they leach chemicals from the plastic to the liquid, some of which may be toxic. Put the question the other way, what exactly is the advantage of using plastic containers instead of glass ?  Also, how do you explain bottled water having an expiration date, if not from leaching of chemicals into the water ? StuRat 19:53, 12 August 2006 (UTC)


 * yes there is a reason for no plastic pickle jars, and it has nothing to do with leaching of plastic components. a lot of plastics are actually rather permeable to oxygen, much more so than glass, so putting pickles in plastic would result in them not keeping as well. and the acidic point you have confused with items in metal jars, such as aluminium. here liquid acidity plays a role, becuase it reacts with the metal surface, contaminating the food with metal ions. Xcomradex 02:13, 12 August 2006 (UTC)


 * Acids dissolve many things, not just metals. And avoiding plastic bottles, because you don't want food that has been oxidized, is yet another good reason. StuRat 19:53, 12 August 2006 (UTC)


 * See, this is why I avoid this kind of "omg it's bad more me" thinking. It always turns out to be misinformation crud. --mboverload @  09:37, 12 August 2006 (UTC)


 * A lot of people's opinions/facts here seem to contradict each other. Does anyone have a viable source for this information? --Proficient 13:39, 12 August 2006 (UTC)


 * Well, the source for the info that plastic water bottles have expiration dates on them is the bottles themselves, go look at some in the store. StuRat 19:56, 12 August 2006 (UTC)


 * It is true, however, that very few studies have been done in this field. The reason is that government food health regulation organizations, like the FDA, don't consider containers to be under their jurisdiction, and food companies, unless forced to do so, have no interest in paying for a study that may make them liable for damages and/or force them to change their packaging. StuRat 20:13, 12 August 2006 (UTC)


 * Well, in addition to the Snopes link I provided above, here is another. Why use plastic rather than glass? Because it's much lighter weight and less prone to breakage. Broken shards from a heavy jar are, I daresay, more dangerous to my health than plastic compounds in my food. I have indeed seen red pasta sauce packaged in plastic bottles, as well as items such as pickle relish. As for expiration dates on bottles, I had always assumed this was a marketing ploy, in which companies hope consumers will throw out old bottles and purchase new ones, although I could be wrong. --Ginkgo100 talk · contribs · e@ 23:26, 12 August 2006 (UTC)


 * If you're going to go that far in finding risks in glass jars, how about empty plastic containers, set too close to the stove, catching fire, spreading to the rest of the house and killing your entire family ? Now, if we can keep the discussion reasonable, what are the risks of glass bottles which are used properly (which doesn't include smashing them and jumping up and down on the shards) ? StuRat 04:37, 13 August 2006 (UTC)


 * I once had a beer bottle with a splinter broken off the top. I decided not to take any chances and threw it down the sink.


 * Water that has been in a plastic container can indeed taste 'platicy', so I assume some of it does dissolve. I don't know if bits of plastic eaten by children are harmless because they pass through their system, but dissolved plastic may get absorbed (first into the blood and then where?). The quantities may be minute (I've had water stored in a plastic bottle for years and the bottle was still there :) ), but toxins can be dangerous at extremely low concentrations and I don't know if there might be a cumulative effect.


 * I've checked a Spa bottle and there is a date on the lid, but it doesn't say whether that is expiration or production, so I'll assume the latter. Also, I've tried your experiment. Be back with you in ten years. DirkvdM 10:07, 13 August 2006 (UTC)


 * You can tell if it's a production date or expiration date by whether it's long ago (production date) or in the future (expiration date). If the date just passed, then either you just bought it hot off the production line or it's quite old and that's the expiration date.  As for kids eating chunks of plastic, some portion of the plastic would dissolve, or leach out, but the relatively short period inside the body (about a day) means that not much leaching will occur.  A water bottle left on the shelf for years, especially if in the hot sunlight, on the other hand, has plenty of time to leach toxic chemicals into the water. StuRat 19:29, 14 August 2006 (UTC)

Potency of liquid explosives
With the recently foiled plot to blow up passenger airplaines by mixing liquid explosives, a danish expert on television explained that as little as 100ml explosives would be enough to blow up a plane. That's some pretty intense firepower, if you ask me. The article on organic peroxide isn't very helpful in determining how explosive it is, but I would assume the exact details on where on the plane the explosion is placed is important. Merely blowing a small hole in the fuselage clearly isn't enough.

Is the terrorists plan even feasible? Could a skilled pilot land a damaged plane on the sea, if the plane is only partially destroyed?


 * Merely blowing a small hole in the fuselage clearly isn't enough. Pardon 8-? Have you ever made a small hole in a balloon? What happens?--Light current 13:39, 11 August 2006 (UTC)


 * I was under the impression that the bulk of air travel is not by balloon these days? Blowing a small hole in a plane's hull will have extremely uncomfortable effects and will probably cause a few deaths, but it would not necessarily induce the plane to crash. dab (&#5839;) 13:51, 11 August 2006 (UTC)


 * I too must have miised it when they unpacked and inflated the planes at heathrow. Philc  TECI 20:25, 11 August 2006 (UTC)


 * What you mean you can breathe ok at 30000 ft?--Light current 14:06, 11 August 2006 (UTC)


 * no, why? dab (&#5839;) 14:18, 11 August 2006 (UTC)


 * Lack of oxygen after being sucked thro a window! (or decompression) See altitude sickness--Light current 17:29, 11 August 2006 (UTC)


 * I would have to side with the pessimists. A small hole in an otherwise smooth airframe travelling 450MPH at 30000' is nothing short of catastrophic.  If you're lucky, the plane might make it down in one piece.  If you're even more lucky, it will do so on a runway or other suitable facility.  The article on Oplan Bojinka has more details relevant to the question at hand, which is how much damage could a little explosive do to an airliner.  The 'successful' 1994 Manila Air bombing had 1/10th the intended quantity (for 'testing purposes') and was enough to kill one, injure 11, and force the plane to perform an emergency landing. --66.195.232.121 14:19, 11 August 2006 (UTC)


 * The effects of explosive decompression vary; see for example Turkish Airlines Flight 981 and Aloha Airlines Flight 243. --Lambiam Talk 14:59, 11 August 2006 (UTC)


 * I would actually interpret the Philippine Airlines Flight 434 bombing differently: a bomb big enough to split a man in half makes a hole in the plane, and the plane lands succesfully. Death and injuries were caused by the explosion, not by the hole. The real damage to the plane comes from any avionics that are affected (hydraulic and electrical wires traveling throughout the plane). Bomb: death, fire: death, damage to avionics: death, air leakage: discomfort. The only place where decompression instantly kills you is Hollywood movies. Reading material: Cabin pressurization, (from the first page of google results for plane hole myth). Weregerbil 15:04, 11 August 2006 (UTC)


 * The plane showed surprising resiliency, but it was only subject to 1/10th the nominal explosive volume. Decompression is one thing, a huge hole in a fuselage is quite another.


 * I commonly see the argument that a pinhole in a plane will take it down. My father has worked all his adult life as an aircraft mechanic.  His job is repairing holes on the body of passenger jets.  Every flight puts holes all over the plane.  Lightning turns it into, as my father describes, swiss cheese.  So, am I to believe that my father has not been working his whole adult life and not only made up the story of fixing holes in the plane's body but also faked the repair shop I visited him at and all those body sheets with little holes in them that he was filling in? --Kainaw (talk) 17:45, 11 August 2006 (UTC)


 * A pinhole wont take it down, but what about a 2" dia hole? See explosive decompression Also there is a way to stop a balloon exploding when puctured with a pin. Put a piece of sticky tape on the surface first then ouncture thro that. Does this tell you anything about the problem? It should!--Light current 17:51, 11 August 2006 (UTC)

....And dont say all planes should be wrapped in sticky tape!--Light current 18:02, 11 August 2006 (UTC)

A small hole would cause the cabin to decompress slowly. Note that the air is nowhere near a vacuum at the altitude planes fly, however. The problem becomes breathing in the thin air. The oxygen masks would drop, and that would allow the passengers to breath. The pilot would also likely decide to lose altitude to a point where people could breath without the oxygen masks. Also note that it takes some 10 minutes to die from total oxygen deprivation, while we are only talking about a slight reduction in the oxygen level (due to the thin air), so it might take hours for people to die, even if they had no oxygen masks and stayed at high altitude. Finally, an emergency landing would be made at the first available airport (not "in the sea", which would be deadly). The only likely deaths would be as a result of the explosion and from heart attacks, due to the stress. StuRat 18:21, 11 August 2006 (UTC)


 * Assuming you had oxygen to breathe, its a question of whether the low pressure or the rate of decompression, or the extremely low temperatures would kill you. Im not certian after looking at a number of our pages on related subjcts. I suppose it depends on how fit you are, and how long you are exposed to this environment. 8-(--Light current 18:36, 11 August 2006 (UTC)


 * A small hole wouldn't cause much of a temp drop, except right around it. I should think the heating system on board could easily keep pace with the heat loss through the hole, especially once the it was plugged (this might even happen automatically, if a blanket or pillow gets sucked up against it).  Another effect would be noise.  It might be quite loud near the hole, causing hearing damage to those nearby. StuRat 23:58, 11 August 2006 (UTC)


 * Loss of cabin pressure isn't a deadly incident, surely. But you all seem to think that a large nitroglycerin bomb going off inside an airplane would be a casual occurrence!  A huge bomb blowing a gaping hole in the side of an aircraft at altitude is certainly cause for concern in my book.


 * Loss of cabin pressure at altitude (e.g. 35000ft) is certainly deadly. See Helios Airways Flight 522 and Payne Stewart for examples where death was most likely by hypoxia; alternatively if decompression occurs suddenly (e.g. as the result of an explosion or structural failure) the fuselage can be ripped open as happened on Turkish Airlines Flight 981. IIRC, at 35000ft hypoxia can incapacitate the pilot within 15-20 seconds without emergency oxygen following a rapid decompression. In this event the pilots rapidly don their oxygen masks and execute an emergency descent; their vision is likely to be impaired as the pressure drop causes tears to evaporate from the surface of the eye, and they may have suffered severe hearing damage or perforation of their eardrums. Meanwhile any passengers who have failed to get their oxygen masks on can expect to be suffering permanent effects within two minutes, as lowered pressure causes blood oxygen to diffuse back into the lungs. The outside temperature is roughly -56ºC so it is likely to get rather cold rather quickly, even with the heat turned up (although this would obviously depend on the size of the hole). As a result of the emergency descent (to below 18000ft to ensure the safety of passengers), fuel consumption will be drastically increased and range will be correspondingly shortened - if this occurred far from an airport there is a real likelihood of a crash or ditching attempt. --Yummifruitbat 03:11, 12 August 2006 (UTC)


 * Those are the type of things that would happen if a door was blown off, not from a small hole. The Helios timeline also shows that people were still awake 2.5 hours after the cabin pressure alarm went off.  It was human error (failure to react to the situation) which downed that flight. StuRat 04:46, 13 August 2006 (UTC)


 * I won't be doing any guesswork here, just quote a guy from an 'national emergency team' (something along those lines) who said that a bomb could blow a hole in the hull that, if strategically placed, could crash the airplane. He didn't say where that place was and why it would crash the plane, though. DirkvdM 10:18, 13 August 2006 (UTC)


 * Even if the cabin was depressurized don't they have really thick metal doors around the cabin>? meaning that the pilots could still land the thing without any problems?--71.247.125.144 14:58, 13 August 2006 (UTC)


 * I think you're saying the cockpit is a separate pressurized chamber from the passenger compartment. This is not the case, they share the same heating and A/C system, and those common ducts keep the pressure equal between the two parts of the plane. StuRat 19:21, 14 August 2006 (UTC)

Strength of HCL
There is an experiment for calculating the strength of HCL. It is a titration using NaOH. After the titration I used a formula with the figure 3.646. I multiplied this figure to the mL of NaOH. Where does this figure come from.


 * Roughly speaking, because HCl and NaOH are a strong acid and base respectively (and of roughly equal strength in each direction), it takes 1 mol of HCl to neutralise 1 mol of NaOH, with a result that is pH neutral - 7. So if you have 10 mL of 1 M NaOH, then that's 0.01 mol of NaOH, which has to react with 0.01 mol of HCl. If that takes 5 mL of HCl, then you have 0.01 mol / 5 mL = 2 M, for example. Your calculation probably has that kind of reasoning hidden in it somewhere. Confusing Manifestation 15:05, 11 August 2006 (UTC)

Damn edit conflicts!! :)


 * So, the titration probably told you that $$V_{NaOH}$$ mL NaOH of a given molarity $$M_{NaOH}$$ neutralized $$V_{HCl}$$ mL HCl of unknown molarity $$M_{HCl}$$.
 * $$M_{NaOH}$$ has units of moles/L, and you want a value in moles, so you probably multiplied the number of mL of NaOH by $$\frac{M_{NaOH}}{1000}$$ (since you measured the NaOH in mL not L).
 * So, $$ N_{NaOH} = V_{NaOH} \frac{M_{NaOH}}{1000} $$. $$N_{NaOH}$$ is the number of moles of NaOH used.  Since NaOH and HCl both separate into only two ions, you can simply take $$M_{HCl} = 1000 \frac{N_{NaOH}}{V_{HCl}}$$ to get the molarity of HCl.  I'm not sure which one of these numbers was 3.646, but it probably depended on what molarity of NaOH you were using to do the titration.  --Bmk 15:09, 11 August 2006 (UTC)


 * The molar mass of HCl is given as 36.46 g/mol. Was there a factor of 0.1 mol/l for the NaOH? --Lambiam Talk 15:24, 11 August 2006 (UTC)


 * Please don't confuse the strength of an acid with its concentration. I suspect the original question was to calculate the mass concentration of the HCl, with units in g/l. HCl is a strong acid at all times, but it can be made dilute or concentrated by altering the ratio of acid to water.--G N Frykman 17:52, 11 August 2006 (UTC)


 * Well, the question is ambiguous. Depending on the circumstances, titration could measure either "strength" or concentration.  --Bmk 19:54, 11 August 2006 (UTC)

The strength of the acid - how much it ionises - would be calculated by conductivity measurements. Titration will only tell you the concentration of the acid, and won't tell you whether it is strong or weak.--G N Frykman 09:41, 12 August 2006 (UTC)

Thermodynamics
Hi, I have a question with a bet I am trying to settle, I cannot find the info on wikipedia. Is it possible for a fridge/air conditioner ect to produce more cold then heat? I thought a thermodynamics law stated that it was impossible for it to produce a net cold? Any answers? If so could you provide the law or some reference? Thanks

Hanez


 * A refrigerator merely sucks heat energy from the interior and dumps itoutside the case. You also have the heat produced by the compressor. So the answer is : it produces more heat than cold!--Light current 17:19, 11 August 2006 (UTC)


 * So, yes, Hanez, you are correct, it would violate the laws of thermodynamics for any device to lower the temperature of the universe. StuRat 18:08, 11 August 2006 (UTC)


 * So why do you need a fridge that big?--Light current 18:12, 11 August 2006 (UTC)


 * Maybe so you can put stars inside the fridge to induce cold fusion ? :-) StuRat 18:24, 11 August 2006 (UTC)


 * Stars are already (hot) fusion reactors 8-)--Light current 18:31, 11 August 2006 (UTC)


 * So cool them down, and then you have cold fusion, right ? :-) StuRat 23:53, 11 August 2006 (UTC)

Thanks for the responses. How about heat neutral? Is it possible for a dehumidifier or a fridge ect to produce the same amount of heat as it does cold? Or should it always be producing more heat than cold?


 * That would require 100% efficiency, which never exists in the real world. StuRat 23:53, 11 August 2006 (UTC)


 * You've never seen me at work, have you? Then again, some people claim I'm not for real, so may still be right. DirkvdM 10:23, 13 August 2006 (UTC)


 * You are 100% efficient at spouting nonsense, I'll have to grant you that. :-) StuRat 07:28, 16 August 2006 (UTC)


 * This concept will be much easier to understand if you stop thinking of "cold" as a substance. The best way to think of a refrigerator is an engine that works between two heat baths of different temperatures by taking in external energy.  See heat engine.  A refrigerator is a heat engine working in the opposite direction.  --198.125.178.207 00:53, 12 August 2006 (UTC)

It's actually pretty humorous that the only thing air conditioners do is produce heat overall =D --mboverload @ 01:24, 12 August 2006 (UTC)


 * please do not pull tongues here! thans --Light current 04:34, 12 August 2006 (UTC)


 * And that's not even counting the global warming they cause. DirkvdM 10:23, 13 August 2006 (UTC)

Soda Water
I drink a lot of soda water. I do so to help me prevent from drinking soda. But also cause water is boring and I want to keep hydrated. So, for the latter reason, am I really hydrating myself with soda water? Here are the ingredients on one particular bottle:

table salt, sodium citrate, sodium bicarbonate, potassium bicarbonate, potassium sulfate, or disodium phosphate

Also, does milk hydrate? Thanks!!!


 * THe question is: are any of those substances diuretics?--Light current 17:23, 11 August 2006 (UTC)


 * What do you mean by "hydrated?" If you simply mean "not thirty" than pretty much anything with water in it will do. When energy drink makers talk about "hydration," it's a marketese way of refering to osmotic pressure. When you sweat, you give off not just water but salt. Your body needs to maintain a pretty stable ratio of both, so drinking pure water is not ideal. Electrolytes (ie, salt) help. If you're running long races or hiking in the desert, you need to care about this. Otherwise, it doesn't really matter. --Pyroclastic 17:34, 11 August 2006 (UTC)


 * Why cant you be hydrated even if you are thirty?--Light current 17:47, 11 August 2006 (UTC)


 * I'm way past thirty and still pretty hydrated. DirkvdM 10:26, 13 August 2006 (UTC)


 * Anything with water in it will "hydate" you, it isn't that scientific. — [  Mac Davis ] (talk)


 * Well, your statement certainly isn't. Sea water and whiskey contain water. DirkvdM 10:26, 13 August 2006 (UTC)

Purified water
On the North American cooking show Good Eats, in an episode on making stock, the host Alton Brown mentioned that distilled water was too pure to be good for dissolving the collagen and flavor compounds that are necessary for good stock. I was under the impression that very pure water is "hungry" to dissociate into ions and is therefore a very good solvent, not a poor one. Am I mistaken, or is Alton? --Ginkgo100 talk · contribs · e@ 17:48, 11 August 2006 (UTC)


 * Pure water is an excellent solvent, but is reckoned not to be very good for making tea, for example. This is possibly due to the lack of dissolved air - boiling the water to distil it gets rid of most of the dissolved air. The degree of ionisation of water itself is always very small (it's called the ionic product of water) but it is a wonderful solvent for ionic substances.--G N Frykman 17:57, 11 August 2006 (UTC)


 * Yeah I think its bad to drink pure (deionised) water. It needs some minerals (or whisky).--Light current 18:16, 11 August 2006 (UTC)


 * Well, stock isn't intended as a beverage, but as a food base for sauces and soups. The idea is that some types of water will be better at dissolving substances in the meat, bones, and vegetables and therefore produce a higher quality stock. If the problem is dissolved air, would aerated distilled water be as effective as tap water or artesian water? -- 66.7.182.48 Ginkgo100 talk · contribs · e@ 19:30, 11 August 2006 (UTC)
 * I say Alton Brown is just wrong. It doesn't matter. Once you dump the bones, meat, and vegetables in it's not "purified" anymore anyway. I will say that buying distilled water for food purposes is a waste of money. --GangofOne 19:51, 11 August 2006 (UTC)
 * His claim was that there was a negative benefit to using distilled water (as is not usually the case in cooking, since you want the purest ingredients possible) since normal water has a baseline of impurities that works toward bringing more flavor out of the stock. Also, saying that using purified/distilled water for food use is wasteful, is a matter of complete opinion as many culinary experts and food connoisseurs would argue the opposite and can easily tell the difference in food prepared with purified water versus typical tap water.

There is a well-known (among protein biochemists) phenomenon of "salting in" proteins. First google hit: "Initial salting in at low concentrations is explained by the Debye-Huckel theory. Proteins are surrounded by the salt counter ions (ions of opposite net charge) and this screening results in decreasing electrostatic free energy of the protein and increasing activity of the solvent, which in turn, leads to increasing solubility. This theory predicts the logarithm of solubility to be proportional to the square root of the ionic strength." (source) For protein solubility, the pH of the water can also be important. --JWSchmidt 22:35, 11 August 2006 (UTC)


 * but that is irrelevant, once you dump meat etc in the water (full of ions etc), you no longer have pure water. i'd say the amount of ions in the water (generally on the ppm level for most ions) contributes only the tiniest amount to the amount of ions in stock (which will be much much more). i'd say your cook is talking smack. Xcomradex 02:08, 12 August 2006 (UTC)


 * Well, that could very well be, but Alton is normally quite good with his science, is a trained chef, and makes copious use of various food scientists in his episodes, so he'd seem to be in a position to know. When you add something to distilled water, you are obviously adding impurities, but perhaps not the same kinds of impurities that would be found in "normal" water.  Our article on distilled water is spectacularly uninformative and google searches are cluttered with nutcases pro- and anti- for drinking distilled water, so it's difficult to tell.  Alton has a website, so I guess we could ask him to explain himself. Matt Deres 03:02, 13 August 2006 (UTC)
 * A link I added to a question on one of the Reference Desks about using honey in homemade beer said specifically not to use distilled water for beer.--Anchoress 03:06, 13 August 2006 (UTC)
 * But why? Just because somebody, an unknown person who has a computer, said that doesn't make it true. --GangofOne 04:10, 13 August 2006 (UTC)
 * 1) I'm not saying it's true, I'm saying someone said it. 2) I don't know why, and I don't think I'm obligated to figure out why. 3) It wasn't just 'somebody, and unknown person who has a computer', it was the corporate website for a brewery, answering questions about how to optimise home brewing. Please don't jump down my throat for trying to be helpful. Anchoress 04:19, 13 August 2006 (UTC)
 * I assure you I am not, and have no interest in, attacking you. My only interest is a deeper understanding of reality. --GangofOne 06:56, 13 August 2006 (UTC)
 * According to The Complete Joy of Homebrewing, 3rd ed., by Charlie Papazian, whether distilled water is appropriate for homebrewing depends on whether you're doing a malt-extract beer or an all-grain beer. Malt extract contains adequate minerals, so distilled water is acceptable (p. 78). The chapter on "advanced homebrewing" (applying to all-grain brewing) does not explicitly state one should not use plain distilled water, but does imply it, because certain minerals are needed for a good mash. --Ginkgo100 talk · contribs · e@ 22:00, 13 August 2006 (UTC)

British bombing plot explosives ingredients
Reportedly (I am not too impressed by the news media's facts), the bombers planned on using liquid mixtures in British sports drink bottles to make an explosion. Does anybody have any guesses to whether or not this is true, or what chemicals they were planning on using? — [  Mac Davis ] (talk)


 * There was a demonstration on the TV last night by a Professor of chemistry (or something like that) who took some simple ingredients making a mixture of 200 ml or so. He placed this on top of a (5mm?) steel plate, ignited it, and it made a neat hole about 30mm across. Draw your own conclusions.--Light current 18:43, 11 August 2006 (UTC)


 * So basically if the self destruct button on the plane is hidden behind a 5mm steel plate, you can punch hole in it and press the button. Otherwise you'll need something better. Philc  TECI 21:09, 11 August 2006 (UTC)


 * The article on the 2006 transatlantic aircraft plot mentions some possible mixtures. Some of the articles listed in the "see also" section describe what has been used in other strikes. Weregerbil 18:45, 11 August 2006 (UTC)


 * I read somewhere that a mixture of acetone and concentrated hydrogen peroxide was likely. --Pyroclastic 18:58, 11 August 2006 (UTC)


 * I thought of this as a possibility, but I don't know. --Bmk 19:58, 11 August 2006 (UTC)


 * Nitroglycerin has been used by terrorists in at least one aircraft bombing, although it did not succeed in destroying the aircraft. If carefully positioned in a vulnerable location, and possibly combined with other components to generate shrapnel, I'm sure this could potentially be used to cause a crash. --Yummifruitbat 23:13, 11 August 2006 (UTC)


 * Look up binary explosive. Also keep in mind that aircraft skin is made of aluminum and is a lot thinner than that 5mm steel plate.  Something that can blow a one-inch hole in that plate can create a hole five feet across or more in an airplane. --Serie 21:51, 11 August 2006 (UTC)

I have no idea how aircraft keep a balance between internal and external air pressure. Would it be possible for a gas generator of the type used in airbags to produce so much gas in a short period of time that the skin of an aircraft could rupture and pop open? --JWSchmidt 22:43, 11 August 2006 (UTC)
 * I think such a device would need to produce a phenomenal amount of gas - remember that an aircraft fuselage is itself a pressure vessel and is designed to withstand a considerable pressure differential. I think causing a rapid (i.e. explosive) decompression would be more feasible, particularly since this has the potential to incapacitate the crew even if the aircraft is not destroyed by the explosion. --Yummifruitbat 23:13, 11 August 2006 (UTC)


 * bearing in mind a fire on board an aircraft is a rather serious issue, i'm sure simply spreading 100 mL or so burning flammable liquid around could cause a fair amount of disruption. and 100 mL nitroglycerin would cause a tremendous amount of damage, given (a) it is 1.5x more powerful than TNT, and (b) it has a reasonable density. so 100 mL nitroglycerin would be about 117g, which would be equivalent to around 175.5g TNT. for comparision, in a hand grenade there is about 180 g Composition B. so you could certainly do a lot of damage to a soft aluminium shelled aircraft. Xcomradex 02:03, 12 August 2006 (UTC)


 * just a thought, i bet a chemically aware terrorist could make some pretty clever bombs, say a concentrated solution of diazomethane or neat phenyldiazomethane. i imagine its the last thing sensors are looking for. or even something around organic azides, eg diazidomethane. i imagine we aren't getting the whole story out of the respective govts, especially since a lot of sensitive compounds (eg TATP?) become a lot less sensitive in solution. Xcomradex 02:24, 12 August 2006 (UTC)


 * and i am entertaining the thought of panclastite type explosives being what was going to be used, easily prepared from relatively inert and readily availible ingredients. Xcomradex 02:30, 12 August 2006 (UTC)

Instead of bombs, Andrew Sullivan suggests instead that the weapons might be the "terrorist breakthrough" device called a "mubtakkar" that quickly evolves a large quantity of hydrogen cyanide gas. Via a report in Time magazine. -Wfaxon 07:38, 12 August 2006 (UTC)

Speed of Smell
Is there any way to quantify the speed of smell? Here is a crude example but its the first to come to my mind; sometimes when I fart, I smell it right away...other times it takes a while. Well, not that I think about it wind, humidity prolly are factors in this. But is there anyway, in like a controlled in environment, that the speed of smell can be quantified?


 * It just depends how fast the smelly molecules are travelling. THis of course depends on the air velocity in the vicinity. If you were to fart downwind, the smell would travel woth the wind (hopefully) at its speed. I predict this question will attract a great many comments (some funny, some not).--Light current 18:47, 11 August 2006 (UTC)
 * Brownian motion ? :-) StuRat 23:46, 11 August 2006 (UTC)
 * I guess the speed of a fart would be the speed of any air currents that are present combined with entropy in the form of Brownian motion. Weregerbil 18:51, 11 August 2006 (UTC)


 * Yes I think you are correct. Plus of course the exit velocity from the offending orifice?--Light current 18:53, 11 August 2006 (UTC)


 * Well this is an odd question. Well if we're talking about the time it takes for the " smell " to reach you that would be depend on the speed at which the particles involved move. You should note that a cloud of particles isn't a " smell ", it becomes one when it interacts with the receptors in your nose. I think Olfaction might be a good read for you PvT 18:54, 11 August 2006 (UTC)


 * Besides air currents, the main factor affecting the "speed of smell" is simple diffusion. (A question for others with a better understanding of physics: Is there a known rate of diffusion in still air? Would it depend on air pressure?) A more concentrated odor will seem to travel faster than a less concentrated one because the threshold of molecules necessary to detect it will reach the nose faster. -- 66.7.182.48 Ginkgo100 talk · contribs · e@ 19:27, 11 August 2006 (UTC)


 * I believe small molecules diffuse faster, and diffusion speeds up at higher temps and lower air densities. It some cases, the rate of diffusion in air is amazingly high. StuRat 23:44, 11 August 2006 (UTC)


 * For biomolecules, which are relatively heavy compared to air, stray air currents (caused by such things as breathing, moving, ventilation, farting, etc) are usually much more efficient at moving odors around than actual diffusion. In perfectly still air an odor could take many hours to cross a room.  In practice people often use an effective diffusion rate which is really not diffusion at all, but an average rate of transport due to all the stray air currents.  Dragons flight 00:05, 12 August 2006 (UTC)


 * I would have thought there are a few factors involved. Firstly, the volatility of the odor source, then the considerations described above on the air currents carrying the volatiles to the nasal epithelium. Then you have to consider the number of molecules required to activate the number of neurons required for our noses to recognise a smell. The next consideration is the rate at which the olfactory neuron can transduce the binding of the odor to its receptor, into an action potential (this is pretty quick when tested experimentally). Then you have to consider the neural circuitry (the details of which are currently unknown) as the activated olfactory neurons project to their glomeruli in the olfactory bulb and pass the signal on to mitral cells, which in turn project to regions of the cortex. Once there, we recognise the "smell". One would think the speed of the signal along the neural circuitry would be pretty repeatable, thus the variation would most likely be at the level of odor detection, reception and transduction, especially considering its know we undergo adaptation to odors (though the mechanism not fully understood).  Rockpock e  t  01:52, 12 August 2006 (UTC)

We used to perform a simple experiment for our Year 9 pupils (UK: 13-year-olds) in which we took the lid off a gas jar of hydrogen sulphide in one corner of the laboratory, and got the pupils to note at what time they could detect the smell, and plot iso-smell (?) contour lines. It used to take about 20 minutes for the smell to get from the front to the back of the laboratory - which was way too fast for the theoretical speed of diffusion of hydrogen sulphide. There were many factors to consider, of course - the fidgeting boys, the heat each one was giving off, air currents from under the door and so on. When hydrogen sulphide became politically incorrect, as it were, we used a squirt of lemon-fragrance air freshener. --G N Frykman 09:34, 12 August 2006 (UTC)


 * Nice experiment! However, i guess you would also have consider the competition among kids to be the first to smell it and the natural variation among individuals to odour sensitivity. The interesting thing would be to see if different odor classes (that are thought to activate different receptor subclasses) but with the same volatility, showed different iso-osmic contours. That way we would begin to get an idea of the rate distinct odors are detected and transmitted. *starts writing grant*  Rockpock e  t  20:31, 12 August 2006 (UTC)


 * I wouldn't tell them in advance what the odor is. Then, record when they say that they smell something and what they think that they smell, at that time.  If they get the odor wrong, ignore their input. StuRat 20:44, 12 August 2006 (UTC)

Anything exceeding that smell would be, ehm, ultra-olfactoric? No article on that yet? Ultra-smelly? Nope. Suggestions? DirkvdM 11:31, 13 August 2006 (UTC)

Speakers
Can you assume that speakers are producing sound within the limits of their construction if there is no sound distortion? Or would it not be unreasonable to expect a speaker burst after cranking the volume a bit too high, even if it was producing clear sound just before bursting? freshofftheufo ΓΛĿЌ  19:44, 11 August 2006 (UTC)


 * I would say : yes--Light current 04:54, 12 August 2006 (UTC)


 * Without much knowledge about the science behind speakers, I would say no. --Proficient 13:53, 12 August 2006 (UTC)


 * think you will hear some bad noises before the speaker bursts. Thats the time to turn down--212.74.96.197 23:52, 12 August 2006 (UTC)
 * As someone who knows a fair bit about speaker application, I can say you certainly can damage them without hearing a thing beforehand. The chief killer of speakers is overheating and eventual distortion of the voice coil.  A speaker is basically a big electric motor, that moves back and forth along its center axis, instead of spinning.  Like anything (beisdes a Superconductor) that moves electricity, some energy is lost to heat.  What happens to the heat, you ask?  It builds up within the coil, and if it cannot dissipate fast enough it can cause breakdown of the magnet (leading to a dull ineffective speaker), or complete thermal runaway (leading to meltdown of the coil).  Now, most well made speakers take this process into account and can dissipate the heat fast enough at peak output.  Also, a cone built too thin, or a rubber surround that isnt wide enough, can fail prematurely due to heavy use with little warning.  What's the moral of the story?  Expect cheap speakers to fail, unless you listen very delicately.  If you want something that sounds good AND lasts, do some research and pick out a well made brand. --24.210.26.146 23:58, 12 August 2006 (UTC)


 * no I dont go with this run away thing. you can burn the coil but thats if you put too meuch volts on it, but you will hear it long before that happens.--212.74.96.197 00:10, 13 August 2006 (UTC)


 * Right, but since more than 90% of the energy in most speakers is converted into heat energy, it seems to make sense that a speaker would "burn out" at high volumes. It would explain why speakers burst below max capacity after they have been used for a while, when natural corrosion isn't an issue. Thanks for the answers! freshofftheufo  ΓΛĿЌ  06:13, 13 August 2006 (UTC)

Monogamy
As I was reading Brian Skyrms' book Evolution of the Social Contract and as he was discussing the evolutionary fitness of various strategies of division of a cake (greedy (2/3) vs. just (1/2) vs. modest (1/3)...) I wondered how monogamous relationships affect the evolutionary fitness of a species. On a naive level it seems that monogamous (especially lifetime monogamous relationships) would decrease the genetic variation of a species' off-spring, which seems (at least on my understanding of evolution) decrease the fitness. But likewise, if monogamy in that species is particularly helpful in raising well-adjusted adult members then that increases the fitness of the off-spring. Does anyone know of any semi-technical (or even technical, I guess I can attempt to read technical articles even though my major is philosophy) material on this subject? I'd imagine if you could find a species with monogamous relationships and a closely related species without that type of relationship, then you could get a beautiful study on how monogamy affects the evolutionary fitness of a species (insects would be great given their short life-time). And if my admittedly naive understanding of the complexities of evolution is wrong, then please point this out.--droptone 20:45, 11 August 2006 (UTC)


 * You should also factor in the venereal disease spread by polygamy. StuRat 23:38, 11 August 2006 (UTC)

There has been a significant amount of research on monogamy using rodents, for example, see: Prairie Vole. You might also be interested in this. --JWSchmidt 00:13, 12 August 2006 (UTC)


 * The thing is, long-term pair bonds for the purpose of raising offspring does not require monogamy. IIRC animal studies have shown that many of the animal species that supposedly mated for life had paired females who 'stepped out' with other males (bald eagles were an example they gave). Furthermore, another thing I read (sorry, don't have links and too lazy to look) said that something like 50% of Europeans with royal blood had DNA that indicated unknown paternity somewhere in their ancestry. Aaaand... it's the opinion of some paleo-sociologists or whatever they're called that this explains the evolution of the 'Alpha' vs 'Beta' males; 'cavewomen' chose Alpha males for their ability to protect and provide, but while the Alphas were out hunting, they were canoodling with the Beta males who were hanging around the camp. Remember, the postman always rings twice. Anchoress 00:21, 12 August 2006 (UTC)


 * But does the postman always bang twice ? :-) StuRat 19:35, 14 August 2006 (UTC)

The Strange Case of Diabetes, Genetics, and the MP
Recently my MP Dr Ian Gibson (who's a nice bloke, for a politician) said that a rise in diabetes in Norfolk may be due to inbreeding. Now, naturally, us in Norfolk were not too happy about being portrayed as a bunch of inbred hicks, and scientifically I would question if Norfolk actually is significantly more inbred in this day and age than anywhere else in the UK. Dr Gibson later said his remarks were not meant to cause offence: he meant the term in a "scientific" sense (he has a degree in Genetics), which I guess means that he meant "the rise is caused by a small genetic pool" rather than the more unscientific and offensive "the rise is because my constituents are incestous". But I wonder if he's not using his badge as a geneticist to say "I didn't mean to offend, I meant something completely different because I'm a Scientist." Sorry for the long-winded question. Sum0 21:58, 11 August 2006 (UTC)
 * I read what Ian Gibson said and I think he was commenting on type 1 diabetes in much the same way that geneticists would normally discuss the possibility of a genetic basis for a disease. I doubt if he entertained any thoughts about incest in Norfolk. There can be a founder effect leading to high rates of certain genetic diseases is a population without any incest in a population. --JWSchmidt 22:17, 11 August 2006 (UTC)
 * I read about this story myself this morning and felt a bit sorry for Dr Gibson. Geneticists, among whose number i count myself, talk about "inbreeding" and "outbreeding" in a very matter-of-fact way, without any negative connotation the the general population may attach to the terms. Lab mice strains, for example, are divided into inbred and outbred lines, and these have implications on their fitness and use in disease models. His major mistake IMHO was, when referring to humans, was not using a less emotive term such as consanguinity, if indeed that was his point. As an aside, and at risk of offending our East Anglian friends, i used to live in rural Suffolk and remember as a child an elderly neighbour telling me how she never travelled more than 30 miles from her village until the age of 25, by which time she had already met her husband and had children. She also told me that people used to know which nearby village an individual was from based on their villiage characteristic, such as a squint, polydactyly or big ears. Of course, this is just the testimony of an old woman, but it did make me think Gibson has a point.  Rockpock e  t  01:31, 12 August 2006 (UTC)
 * Heh, no offence taken. I wouldn't doubt that a century ago there would have been a lot of inbreeding, but there's obviously a lot more migration these days and so I wouldn't think inbreeding would still be a noticable factor. I have a strong interest in genetics myself, so the fact that I didn't "get" his reasoning puzzled me. Sum0 19:45, 12 August 2006 (UTC)


 * I agree, i would think these days the level of homozygosity in Norfolk would be not significantly different from another other rural-ish county (it would be interesting to compare diabetes rates with Suffolk, for example). Gibson's theory would not be a good explanation for a rise in type 1 diabetes, however, if the statistic has been consistantly higher in Norfolk - and since the environmental factors causing the disease are unknown - i guess a significant genetic influence can't be ruled out, due to a historically restricted population. Still, this whole saga is somewhat Partridge-esque.  Rockpock e  t  22:53, 12 August 2006 (UTC)

Camera Zoom
Are there any cameras where the zoom mechanism is internal to the camera body, so that the final (first?) lens remains stationary? (I mean on normal commercial cameras, not wacky specialist ones). -- SGBailey 22:18, 11 August 2006 (UTC)


 * wow that would be cool..Wjlkgnsfb 02:58, 12 August 2006 (UTC)


 * Yeah! The Kodak EasyShare V570 has an internal zoom mechanism. --jpgordon&#8711;&#8710;&#8711;&#8710; 03:26, 12 August 2006 (UTC)


 * See also digital zoom (which is not true zoom) and click on "what links here" for a list of cameras.--Shantavira 06:52, 12 August 2006 (UTC)


 * Digital zoom is worse than no zoom at all, it just makes a big blurry mess, don't ever use it. StuRat 19:37, 12 August 2006 (UTC)


 * Except when taking pictures of UFOs and Nessie. freshofftheufo  ΓΛĿЌ  19:40, 12 August 2006 (UTC)


 * Well, of course UFO pics are blurry. If you just had an anal probe you would be more concerned about getting home to your trailer park than focussing the camera, too, wouldn't you ? :-) StuRat 20:48, 12 August 2006 (UTC)


 * If they weren't blurry, the flying object could be identified and it would become an IFO. Wow! I make something up and we've got an article on it! DirkvdM 11:37, 13 August 2006 (UTC)

Smoking and lung cancer
Okay, I managed to find in tobacco smoking that a person who smokes tobacco is 25 times more likely than a non-smoker to develop lung cancer, but I can't seem to find the answer to this question: what pecentage of smokers die of and/or are diagnosed with lung cancer? Better still, good reference desketeers, does anybody happen to kow where I could find to access the approxiamate pecentage of all common causes of tobacco smokeing-correlated death among smokers, seperate from non-smokers? A pie chart (I like pie) would be striking gold. Many thanks in advance. – ClockworkSoul 22:37, 11 August 2006 (UTC)


 * http://www.cancer.org/docroot/PED/content/PED_10_2X_Smoking_and_Cancer_Mortality_Table.asp


 * Unfortunately, this only has cancers, not other causes of death, but take a look at the "PAR" column. Lung Cancer has an 88% PAR, which means that out of 100 cases of lung cancer, 88 were caused by smoking.


 * Also, you may want to check out some NCHS resources like this :http://www.cdc.gov/nchs/datawh/statab/unpubd/mortabs.htm


 * there's a ton of CDC/NCHS/NIH data to wade through on mortality...