Wikipedia:Reference desk/Archives/Science/2008 September 6

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September 6

Potassium Carbonate as a Fire Supression Agent

The Scientific American website currently has a news story [1] about a fire suppression "grenade" which uses potassium carbonate as its active ingredient to suppress fire "at the molecular level". It appears that potassium carbonate/potassium bicarbonate is a common ingredient in fire extinguishers (e.g Purple-K). However, none of those pages mention how it works, except for Purple-K saying it "directly inhibit[s] the chemical chain reaction", with the CO₂ smothering being relegated to a minor role (as expected, since potassium chloride also works in fire suppression). - So what is the mechanism for potassium (bi)carbonate fire suppression? -- 128.104.112.147 (talk) 00:19, 6 September 2008 (UTC)

This old patent seems to indicate that part of it is that heating potassium bicarbonate will release both CO₂ and H₂O. Perhaps that has something to do with it? (I'm no chemist) --98.217.8.46 (talk) 00:45, 6 September 2008 (UTC)

See HowStuffWorks --Russoc4 (talk) 02:36, 6 September 2008 (UTC)

I'm pretty sure I sure something on one of Adam Hart-Davies's shows, where he demonstrated glass fire extinguishers (probably Victorian era). They were roughly grenade shaped and sized, and contained bicarbonate of something. DuncanHill (talk) 09:48, 6 September 2008 (UTC)

Those links don't exactly answer my question. The article potassium chloride (KCl), notes that it works as a fire extinguishing agent, but obviously doesn't have any CO₂ or H₂O to release. HowStuffWorks is claiming that dry chemical fire extinguishers work by smothering the fire by coating the fuel with an "inert solid (similar to dirt or sand)". However, the article Purple-K notes that "Dry Chemical Powder works by directly inhibiting the chemical chain reaction" (the bottom of the fire tetrahedron, versus the oxygen leg of the fire triangle, as implied by HowStuffWorks). The article potassium carbonate notes that aqueous potassium carbonate is used for restaurant fires - so it's not just water release (as they'd use just water), and it isn't smothering with an inert solid (as the dissolved carbonate isn't a solid). - So to clarify my question, I'm looking for confirmation if there is some sort of chemical (versus physical) mechanism of action in potassium/sodium bicarbonate/carbonate/chloride fire suppression, and if so, what the chemical mechanism is. -- 128.104.112.147 (talk) 19:38, 6 September 2008 (UTC)

Consider two Cockatiels, A and B...

Both birds are the same sex and age. Both are descended from many tens of generations of captive-bred stock. Both have been parent raised and kept in an aviary with others of their own kind for their whole lives. A lives in England. B lives in China.

Now suppose that A and B were to be introduced to each other in aviary conditions. Would they be able to communicate and interact with each other in the same way as two wild Cockatiels of the same age and sex from roughly the same area in their natural habitat would - or would there be a significant 'language gap'? --Kurt Shaped Box (talk) 01:23, 6 September 2008 (UTC)

Good question, and I can only imagine they could at least communicate basically. After years of separation in the New World, Americans simply developed a different language from their English ancestors, they don't speak a strange unrelated language called American. Further, any normal bird doesn't answer direct commands like a dog - "sit, fly" etc. Unless, like a parrot, it learns to talk, it's Chinese speaking owners are hardly going to morph it into a different "bird language." Unfortunately it would take a long time to find out, though.78.144.137.205 (talk) 08:51, 6 September 2008 (UTC)

If they wanted to sit around and discuss the current political situation then clearly they would need a common language. But what sort of communication are we talking about. I have never kept these birds but most of their communication is about posture, eye contact, squawking, pecking and scratching. Wouldn't all of that stuff be genetically hard-wired? If you went to a country where you spoke not a syllable of the language I'll bet you could communicate quite a lot without speaking - facial expressions for starters. A smile is a smile and a frown is a frown wherever you go in the world. When you start using language that moves the personal interface (can I say that?) to a higher plane, one not necessarily available to even sibling cockatiels. Richard Avery (talk) 10:17, 6 September 2008 (UTC)

There are really four possibilities here:

1. That parrots learn "language" (or body language or whatever) from their parents. In which case, in your thought experiment, it's likely that the chinese birds would have gradually drifted from the original language - but would that be enough so they couldn't communicate? Who knows? However, you could test this hypothesis with a bird raised entirely by humans who could not have learned from a parent bird and in just one generation would have entirely lost the ability to communicate with others of its species.
2. That parrots have language built in at the genetic level as an "instinct" - and therefore all parrots, no matter how they are raised can communicate.
3. That language is genetic - but that the evolutionary/genetic "drift" would be so rapid that our chinese birds would be unable to understand their English counterparts. This seems unlikely.
4. That parrots don't really communicate with each other much at all making the question entirely moot.

It seems to me that (1) and (4) should be easy to test. If you can eliminate those two then we're down to a genetic/inherited effect - and then if the chinese birds can communicate then it's (2) and if they can't, it's (3).

I presume that such studies have been done for bird-song in general - but perhaps parrots (with their talent of mimicry) are special. That inherent ability to mimic suggests to me that they pick up language from other parrots nearby - so (1) is most likely to be the case and therefore the 'linguistic drift' with the chinese birds may make communication difficult - but perhaps not impossible. But that's entirely supposition based on the idea that mimicry in parrots is there solely to enable them to learn "parrot talk" from their parents and not for some other reason. SteveBaker (talk) 12:25, 6 September 2008 (UTC)

According to Animal_communication#Animal_communication_and_linguistics, Human language is largely learned culturally, while animal communication systems are known largely by instinct, which would suggest both cockatiels would be able to communicate by the same techniques and efficiency as two who were raised in the wild.--El aprendelenguas (talk) 18:26, 6 September 2008 (UTC)

Thanks for the answers so far, folks. As to Steve's comment - I *think* that the main reasons that parrots 'parrot' is to enable the individuals from a certain flock to communicate with each other more easily over distance, or when aggregating with other flocks. IIRC, each bird copies certain unique elements of the vocalizations from the other birds in the local flock (which consists of relatives and trusted associates - friends, basically) to weave a 'song' (yeah, I know - parrots don't really have what we would call a 'song') that is unique to that flock and is recognized by all other members of the flock as belonging to a bird from that flock. Male birds will also attempt to accurately mimic the calls of females when wooing them, also embellishing the 'song' with sonic elements taken from the surrounding environment - which is apparently seen as a desirable trait in a potential mate (and explains why male companion parrots tend to be be better talkers). Sorry, no refs - this is all 'I read it on the web somewhere' stuff... --Kurt Shaped Box (talk) 15:02, 8 September 2008 (UTC)

Winter Solstice

Does this help? SteveBaker (talk) 02:05, 6 September 2008 (UTC)

Did the Winter Solstice fall on the 22nd in 1990?

Or how can I track down that info? It's hard to find old calendars... 128.239.177.28 (talk) 01:29, 6 September 2008 (UTC)Capricorn

How about this? -hydnjo talk 02:22, 6 September 2008 (UTC)

Yes, the solstice was at 03:07 UT on 22 December 1990.--Shantavira|^{feed me} 08:20, 6 September 2008 (UTC)

The answer depends on where in the world you live. The solstice occurred at the same absolute instant everywhere inthe world. This was 1990-12-22-0307h UTC, but this was 1990-12-21-2207 EST.-Arch dude (talk) 11:31, 6 September 2008 (UTC)

And if you happened to be in the southern hemisphere, then the winter solstice was at about 15:38 TDT on the 21st of June. Algebraist 13:27, 6 September 2008 (UTC)

Verily. Inhabitants of the northern hemisphere sometimes think their half is the only half worth worrying about, and is therefore for all intents and purposes the entire world. But we southerners know differently.  :) -- JackofOz (talk) 14:41, 7 September 2008 (UTC)

Awwww. I thought it would be cool to have been born on the solstice, but I was born in Massachusetts, where it seems the solstice occurred on the 21st. So I was born on a plain old non-holiday. I don't suppose anything interesting ever happened on the 22nd of December?

And I apologize if I unintentionally insulted anyone south of the equator. I think Australian and New Zealand accents are some of the coolest in the world, if that helps. 128.239.177.28 (talk) 17:03, 7 September 2008 (UTC)Capricorn

You should read December 22 - that article has a long list of things that happened on that day. In fact, the very day you were born (Dec 22 1990) was "Final independence of the Marshall Islands and Federated States of Micronesia after termination of trusteeship. and you share a birthday with the "famous" French actor Jean-Baptiste Maunier - and you thought nothing interesting happened!...(OK, maybe you have a point!) Hmmm...Disneyland opened on the day I was born! SteveBaker (talk) 18:52, 7 September 2008 (UTC)

I'm not too sure what "final independence" means (they were free for the last time? so they were taken over immediately after that?)and I'd never heard of the Federated States of Micronesia, though according to its article it's a real place somewhere in Oceania. But thanks anyway! I guess I'll have to start watching more French movies to see Jean-Baptiste Maunier... 128.239.177.28 (talk) 13:53, 8 September 2008 (UTC)Capricorn

Drugs that daze or slow down?

1. What category of drug generally slows down your movement or walking speed?
2. What category of drug drug puts you in a daze, e.g. making you only able to do one thing in the time it would take you to do 2 or 3?

(Or names of specific drugs with these effects)--Sonjaaa (talk) 02:18, 6 September 2008 (UTC)

Depressants. --Tango (talk) 02:22, 6 September 2008 (UTC)

Alcohol (EtOH) being the most prevalent. -- MacAddct  1984 ^{(talk • contribs)} 02:33, 6 September 2008 (UTC)

Thorazine is somewhat legendary in it's ability to put people into a slow-moving, slow-witted daze. --Kurt Shaped Box (talk) 02:47, 6 September 2008 (UTC)

1. Drug-induced parkinsonism, notably antipsychotics (of which Thorazine (chlorpromazine) is one). Axl ¤ [Talk] 10:00, 6 September 2008 (UTC)

Maximum Water Vapor In Air

Why is there a specific maximum amount of water vapor that can exist in air at specific temperatures? A similar question would be 'Why is there a dew point temperature for each air temperature?'. I have searched the internet (and Wikipedia of course) and have not been able to pick up this answer. 172.168.186.87 (talk) 03:04, 6 September 2008 (UTC)

Have you read dew point? It doesn't have a very detailed explanation, but it has a brief one. If you want more than that, you'll have to wait for someone more knowledgeable to come along, I'm afraid. --Tango (talk) 03:12, 6 September 2008 (UTC)

As this is a phase transition you have a critical point in the system. --Ayacop (talk) 07:06, 6 September 2008 (UTC)

While that is correct, of course, it's hardly helpful to the OP, I would think. Basically, two forces are at work here: entropy favours all the water molecules to be homogeneously distributed in the form of vapour, while the attractive Van der Waals forces between water molecules favour the water molecules to be close (i.e., favours the liquid form of water). Now, if the certain amount of water in the air exceeds a certain limit (or the temperature drops below the dewpoint), the attractive forces become strong enough to overcome the entropic forces and it becomes energetically favourable for the system to separate into two phases (drops of liquid and the existing vapour). In the liquid fase, the energy of the attractions is low, while in the gaseous state, the entropic contribution to the energy is low, and the fraction of water that condensates will be such that the total energy of the liquids droplets and the vapour together will be lower than the energy of a system where only vapour would be present. --baszoetekouw (talk) 09:40, 6 September 2008 (UTC)

Can you add that to the article? Titoxd^{(?!? - cool stuff)} 02:02, 7 September 2008 (UTC)

Here is a really excellent overview of the process, specifically worded to avoid the rather poor metaphors often employed by textbooks. Further on the website here you can find the replies to the protests you'll make after reading the first page. Matt Deres (talk) 01:56, 7 September 2008 (UTC)

Mystery critter

Mystery buglie

Two questions: 1) What is it, and 2) Why do I keep finding them in supposedly-sealed packages of food? --Carnildo (talk) 07:02, 6 September 2008 (UTC)

I don't have an answer for what it is, but I think you should be writing to your local trading standards officer as well as the Wikipedia Refdesk. SpinningSpark 08:07, 6 September 2008 (UTC)

Where do you live and what is the country of origin of the food?--Shantavira|^{feed me} 08:22, 6 September 2008 (UTC)

Is it hairy? Anthrenus verbasci - larva side (aka).jpg on the German wikipedia [[2]] looks similar! In english it might be a Dermestidae larve.--Stone (talk) 09:13, 6 September 2008 (UTC)

No, not hairy. --Carnildo (talk) 09:16, 6 September 2008 (UTC)

Western US, the food is mostly dry goods (flour, noodles, rice, etc.) from the local supermarkets. I'm not sure if they're inside the packages to start from, or if they've taken up residence in my pantry and are eating their way into the packages. I only rarely spot them outside the packaging, and they're invariably dead when I do find them. --Carnildo (talk) 09:16, 6 September 2008 (UTC)

It looks a bit like a Mealworm beetle larva. --baszoetekouw (talk) 09:43, 6 September 2008 (UTC)

It could be a waxworm the larva of one of the family of Pyralidae moths. Try image googling 'waxworm'. Richard Avery (talk) 10:04, 6 September 2008 (UTC)

I think Richard Avery is right. HERE is a link to one common species of Pyralidae. It can get into small spaces and loves grain products. Do you often see small moths flying around in your kitchen?

If these are what you have, the texture of the infested flour (or other finely ground grain) is likely to be unusual, as if it was impregnated with many tiny spider webs. It could be described as "stringy".

If this is what you have, the nontoxic traps mentioned in the article are worth trying. They are made specifically for this pest and can catch hundreds of moths. If you google "pantry moth trap pheromone" you can find more information. My local hardware store sells the traps. Maybe yours does also. Wanderer57 (talk) 17:10, 6 September 2008 (UTC)

I'd say they're mealworms (I've also seen some bugs that look like the adult beetles in that article), but the larva and adults I've seen are less than half the size mentioned in the article. --Carnildo (talk) 19:17, 6 September 2008 (UTC)

If I can make a recommendation... we've always found that sealing flour and sugar in large glass containers to be the most effective way of deterring pests of this sort. Boxes and bags just don't cut it. --98.217.8.46 (talk) 18:35, 6 September 2008 (UTC)

UK Coal Reserves

The table, entitled 'Proved recoverable coal reserves at end-2006 (million tonnes (teragrams))' in the Coal article, under section 'Production Trends', subsection 'World coal reserves', does not include an entry for the United Kingdom. This source states that there are enough 'untapped coal reserves in the UK to last 400 years.' and this source states that there 'are around 250 million tonnes of coal not yet mined in South Wales' (obviously this excludes the rest of the UK). My question is: Is the table incomplete, are the two BBC reports incorrect, or is there another explanation? I've asked this question on the Coal article talk page, but haven't received a response. Thanks, Daicaregos (talk) 08:24, 6 September 2008 (UTC)

The source for that table has the UK with only 220 million tonnes, which is less than 0.05% of the world total, so wasn't included in our table. The source says that it only includes reserves that are known to be extractable under "existing economic and operating conditions", so perhaps they didn't include all the coal mines in the UK that have been closed with coal still in them. Seems an odd decision - they can be re-opened pretty easily if the need arises. --Tango (talk) 08:06, 6 September 2008 (UTC)

Thanks for your reply, Tango. That makes sense (why it's not on the table). Perhaps the discrepancy between your source and the BBC/Media Wales sources will disappear when they next update their table. We'll see. In the meantime I'll update the United Kingdom, economy section to read reserves of at least 220 million tonnes (It currently says 'The UK has a small coal reserve'. 220 million tonnes doen't seem that small to me though). Would you mind posting the link to the reference please, so I can quote it? Cheers :) Daicaregos (talk) 08:24, 6 September 2008 (UTC)

As usual - let's crunch the numbers guys: Fossil fuel power plant says that a typical coal-fired power station uses 10,000 tons of coal per day. (1 tonne == 1.1 ton) So 220 million tonnes (240 million tons) is only enough to run one "typical" power plant for 24,000 days - about 70 years...or 70 power plants for one year. I'm fairly sure there are more than 70 coal-fired power stations of "typical" size in the UK. So 220 million tonnes is NOTHING...not even a year's supply for the UK. That's hardly a significant reserve - in fact it's such an utterly trivial amount as to be essentially negligable - and it certainly doesn't come close to explaining the "400 years" figure. (And this assumes that no coal is used in other industrial uses - such as coke production - which is needed for steel making and other industrial activities) SteveBaker (talk) 12:09, 6 September 2008 (UTC)

According to one of the tables at [3], Britain uses about 50 Megatonnes of coal a year in electricity generation. I am still digginf for information on the UK's coal reserves, but it should be noted that they declined sharply after the Conservative government's pit closures of the 80s of last century. This is because reserves are usually quoted of coal which is both technically and economically recoverable. The costs of reopening a deep mine are massive (dewatering, propping, ventilation etc), so while the coal may be there, at current prices it isn't worth getting it out. DuncanHill (talk) 12:24, 6 September 2008 (UTC)

And this paper [4] suggests that there is a minimum of 7 billion tonnes of coal in the UK suitable for underground coal gasification. DuncanHill (talk) 12:28, 6 September 2008 (UTC)

This last paper says 'The volumes represent 200 years based on the current UK coal consumption of 64 mt p.a.'. Is this paper correct/worth quoting? Or do you guys think I should just leave the United Kingdom, economy section to people who actually know what they're talking about? Daicaregos (talk) 18:48, 6 September 2008 (UTC)

I think the paper is worth using, (it is from the UK Coal Authority), but do be careful about which of the estimates you use from it, and how you introduce them, as the assumptions on which they are based are important for an understanding of them. DuncanHill (talk) 18:54, 6 September 2008 (UTC)

Well DuncanHill, would you care to make the amendment to the United Kingdom article, Economy section? You seem to know what you're talking about, and we both know that I don't. I only knew that it wasn't right. How about it? :) Daicaregos (talk) 19:27, 6 September 2008 (UTC)

Well, OK, but not straight away, I'll need to read, mark, learn and inwardly digest the paper first - I'm not an expert in this area, just a chap with a love of holes in the ground which have useful stuff at the bottom of them. DuncanHill (talk) 19:44, 6 September 2008 (UTC)

DuncanHill, you're an absolute star. At least you know it'll be right. Many thanks. Daicaregos (talk) 21:01, 6 September 2008 (UTC)

Body Temperature

I heard of an unusual feature where some people's body temperatures are higher than average, at about 100-102 degrees Fahrenheit. Is this condition real and is there a name for it if so?CalamusFortis 15:14, 6 September 2008 (UTC)

Hyperthermia is one of the dangers of congenital insensitivity to pain with anhidrosis because subjects won't feel that they heat up due to the anhidrosis, similar to people suffering from quadriplegia who have the advantage of normal perception above the shoulder, so they can change to lighter clothing before becoming too hot due to the anhidrosis. --Ayacop (talk) 16:41, 6 September 2008 (UTC)

That's a start, but not quite the answer I wanted. The condition of higher than average body temperature occurs all the time. The person's body temperature is normally about 100-102 degrees Fahrenheit, not because the person absorbs too much heat but because his or her body temperature is naturally regulated at 100-102. Is it a symptom of hyperthyroidism?CalamusFortis 17:56, 6 September 2008 (UTC)

There is significant variation of "normal" body temperature between different people - and technically, half of all people in the world have higher than average body temperature while the other half have lower than average. It varies throughout the day and for women, throughout their menstrual cycle. Our pyrexia article says that normal body temperature varies between individuals by about 1 degree F - so someone who is up at 102 is definitely not considered "normal". This makes me suspect that the condition is not in fact "real". The hypothalamus is responsible for temperature regulation. I don't see a name for this problem though...the names seem to relate to the specific causes of elevated temperature. SteveBaker (talk) 18:21, 6 September 2008 (UTC)

If by "all the time" the OP means that this is a common condition, then I would want to see a WP:RS; if "all the time" in rare individuals is meant, then that is more likely. In addition to the work of Phil Mackowiak, my comment is based on personal experience having looking at daily temp curves in thousands of inpatient adults over the past 20 years. There is a distribution in average temperatures in persons without overt infection, but it's a pretty narrow distribution and many of those with higher temperatures are subsequently found to have occult disease conditions. Scray (talk) 19:38, 6 September 2008 (UTC)

I should have clarified. What I meant by "all the time" is that the small number of people who have the condition have their temperatures elevated permanently because their bodies maintain their temperatures that high.CalamusFortis 23:05, 6 September 2008 (UTC)

Crystal Filter and Clocks

1. Are the crystals in the crystal filter same as crystals used oscillator circuits?
2. Can some one direct me to good resource which has details on how Tx and Rx synchronize their clocks.(wireless n/w).
3. Suppose I am using two crystals of same frequency from the same manufacturer and using them in Tx and Rx circuits as clocks(After frequency division from several MHz to say 3 or 4kHz)(No temeperature oven or anything fancy...). Once synchronised, how long will they be in sync(order of magnitude) before requiring resynchronization? Lets say that the the Tx and Rx are in the same house or within 20 to 30 metres of each other so that their environment is essentially the same...

59.93.2.176 (talk) 18:20, 6 September 2008 (UTC)

• 3:you may be able to get a one part per million match in the frequency. Then at 4kHz it would take 250 seconds to drift one cycle. Even in the same house you cannot expect to get identical temperatures. With a good oven you may be able to get 1 in a hundred million stability, and if you need higher periods of coherency with out synchronisation you may wish to use a rubidium frequency reference. Graeme Bartlett (talk) 21:50, 6 September 2008 (UTC)

and, still on #3, how long will they be "in sync" and how frequently they "require" resynchronisation is a function of your application requirements. They're really never in perfect sync; you have to decide what degree of unsync is acceptable. You take the maximum drift (from the crystal's datasheet), do the calculation that Graeme describes, and then compare that to how out of sync you're willing to be. But in the real world you'll resynchronise more frequently than that, to account for worst-case problems in your syncrhonisation scheme, and (this being engineering) an embarassingly large fudge-factor to boot (for all the stuff you don't know to take into account). -- Finlay McWalter | Talk 22:06, 6 September 2008 (UTC)

I'm not sure what the application is here - but generally, in any data transmission system, you use the crystal in the receiver to get you CLOSE to the transmitter's frequency, then use a Phase locked loop to lock into the precise frequency of the transmitter. SteveBaker (talk) 21:58, 6 September 2008 (UTC)

To Steve- The application is that I'm trying to make (as a part of a project) a serial digital wireless transmission system without using custom chips; as I will not learn anything new if those chips do all the work. So I'll try to use only basic stuff like counters, freq dividers, PLLs, decoders, MUXs, DEMUXs etc... Its reinventing the wheel, and may be too advanced or complicated for me...

Well, I'm not sure I want to lock to the carrier itself. Say I'm plannig to use ASK i.e. switching on and off the carrier according to the ones and zeroes; So i want to sync with the switching frequency (bit_rate^-1). If the switching time is a factor of the carrier frequency (i.e if a bit takes up integral number of carrier cycles), then I will implement your idea. So synchronization will need to be done only once (neglecting problems).Thanks

59.93.15.56 (talk) 07:27, 7 September 2008 (UTC)

1. One more question: I did some SPICE sims on a (not so well designed) crystal filter. The loss due to that stage was much more than 3dB. In what range do these filter's insertion(?) losses lie generally?