Wikipedia:Reference desk/Archives/Science/2010 June 22

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June 22

basic physics question about inertia, riding the bus, balance, etc.

When I ride the city bus I stand perpendicular (facing out the window) to the direction of movement (forward). Knowing that we will soon be approaching a stop, I shift my weight to my rear (nearer the back of the bus) leg. Then, as the bus rapidly decelerates, I gradually shift my weight to my front (neared to front of the bus) leg and thereby disperse the change in inertia? velocity? momentum? in a controlled fashion. Done properly, I never need grasp a handrail no matter how abruptly the bus stops. At no time am I off-balance.

What I want to know is: from a Physics standpoint, what exactly is going on here? How can I properly describe this sequence of events? As a layperson, I can sum it up by just saying "shifting my weight and maintaining my balance" but I'm very curious to hear a detailed explanation of the physics involved. Any takers?

Thank you! —Preceding unsigned comment added by 218.25.32.210 (talk) 01:14, 22 June 2010 (UTC)

You are making sure the reactive force on your feet from the floor (well, the total of the forces on each foot) points through your centre of mass (by moving your centre of mass), so that it does not produce a torque. The direction of that force will usually simply be "up", but when the bus accelerates/decelerates the direction changes. You can think of this simply as a change in the direction that is "up", since the equivalence principle tells us that acceleration is indistinguishable from gravity (without external reference, so let's assume the bus's windows are so dirty you can't see out - not a big assumption on the buses I use!). --Tango (talk) 02:05, 22 June 2010 (UTC)

When the bus is not accelerating (bus stationary or moving at constant speed) there are only two forces acting on your body – your weight acts downwards, and the floor of the bus exerts an upward force equal to your weight but opposite in direction. The vector representing the upwards force passes through your center of mass.

When the bus is accelerating there is an extra force – a horizontal force exerted on your feet by the floor of the bus. (If the floor of the bus was slippery with water or ice this horizontal force would not exist. When the bus accelerated you would slide towards the rear, and when the bus stopped you would slide towards the front.)

The horizontal force exerts a torque about your center of mass. When the bus stops, this torque tries to make you rotate (fall forwards.) When the bus is increasing speed, the torque tries to make you rotate in the other direction (fall backwards.) You prevent this from happening by leaning forwards or backwards so that the upwards force exerted on your feet is no longer through your center of mass and exerts a torque on your body. By adjusting the position of your center of mass you can ensure that the torque exerted by the horizontal force on your feet is equal and opposite to the torque exerted by the upward force on your feet. When the two torques cancel you do not rotate (neither fall forwards nor backwards.) Dolphin (t) 02:41, 22 June 2010 (UTC)

I'm not sure that you'd need an external reference (clear windows). All you need to keep from falling over is that the total force vector (gravity + other acceleration) points from your center of gravity to some point on the floor between your feet. This is certainly made easier by seeing the relative motion of a fixed reference frame, but theoretically, at least, it wouldn't be necessary. -- 174.24.195.56 (talk) 15:30, 22 June 2010 (UTC)

You misunderstand me. The external reference is required to tell the difference between the bus accelerating and gravity changing. (Obviously, you know it's the former, but there is no experiment that could actually demonstrate it.) You don't need to know which it is in order to remain upright. --Tango (talk) 16:53, 22 June 2010 (UTC)

Another way to think of this is that when you consider gravity and acceleration to be equivelant, when the bus accelerates forwards, and gravity pulls straight down, the vector sum of those two things is a vector that's as some angle to the vertical. (If the bus accelerated at 1g, it would be a 45 degree tilt). So standing without falling in an accelerating bus is just like standing on a hillside. When you stand on a hillside, you have to put your weight on the 'topmost' foot and brace yourself with the 'lower' foot...and that's exactly what you instinctively do when the bus accelerates. SteveBaker (talk) 19:46, 22 June 2010 (UTC)

A few more questions on quantum mechanics.

Is the observer effect a basic part of quantum theory or a particular interpretation of it? Is the observer effect falsifiable? Is the ensemble interpretation incompatible with the observer effect? And is quantum entanglement a possible explanation for why individual photons might still exhibit interference in a Mach-Zehnder interferometer, regardless of whether they're being observed? ☯  Zenwhat (talk) 02:43, 22 June 2010 (UTC)

To answer your first question: it depends what you mean by "observer effect". If you mean the effect in which observing a system disturbs it (or, in more QM terms, any interaction between two initially isolated systems leavs them in an entangled state) then yes, I think this is a basic part of quantum theory. If you mean wavefunction collapse then I think this is interpretation dependent - in the many-worlds interpretation, for example, there is no objective wavefunction collapse - the apparent collapse of the wavefunction is an illusion due to the fact that an observation implicitly selects one out of a multitude of universes. Gandalf61 (talk) 09:36, 22 June 2010 (UTC)

Another way to look at that is using the classical Schrodinger's cat thought experiment - but without the observer having "special" status:

• The poison gas container became entangled between being closed and being open when it "observed" the quantum event that set off the trap.
• The cat became entangled by "observing" the poison gas canister and is simultaneously dead and alive.
• When the outside experimenter opens the box to look at the cat (and thereby "collapses the wavefunction"), he/she merely becomes a part of the entanglement - and is now the entanglement of an experimenter who is sad for the loss of the cat with an experimenter who is pleased that the cat is OK.
• When the experimenter phones the cat's owner to tell of the sad/happy news - that person on the other end of the line also becomes entangled.
• The telephone system also became entangled between two states where more or less electricity was used for the phone call - the air in the laboratory is entangled between one set of sound vibrations and another - the photons of light reflecting off of the cat and the experimenter are entangled between the two states and head outwards through the laboratory windows entangling other things that they interact with.

In this view, wave functions are not collapsed by some special "observer" - they merely entangle the observer along with everything else. The observer has no special status - which is a much more comfortable position than proposing that human brains are somehow "special". The entanglement ripples outwards (in truth, at the speed of light), affecting more and more things. Since every quantum scale event in the universe is simultaneously entangling different parts of the universe into different states, you effectively have the many-worlds interpretation where every possible quantum event creates an entire new copy of the universe that is an 'entanglement' of all of the other copies. SteveBaker (talk) 10:47, 22 June 2010 (UTC)

It is important to caution that the observer effect is not the same thing as the uncertainty principle. The latter is an intrinsically quantum mechanical effect that is anavoidable. The former can be present in quantum mechanics, classic mechanics, and any other theory for that matter, and is avoidable in principle though it may be hard to avoid it in some experiments. Dauto (talk) 23:10, 22 June 2010 (UTC)

Fossil fish

Hello, does anyone know what kind of fish this is? Thanks, --The High Fin Sperm Whale 03:25, 22 June 2010 (UTC)

It tells you right in the file description. TheGoodLocust (talk) 03:46, 22 June 2010 (UTC)

He's the one who uploaded the file, so I think he wants a more specific answer than the file description. ☯  Zenwhat (talk) 03:57, 22 June 2010 (UTC)

I would imagine that HFSW knew that, since it is his photo. "Ray-finned fish" is not a very specific description. There are more species of ray-finned fishes than all other vertebrates put together. Anyway, I'm certainly not an expert, but it looks very generic to me. Looie496 (talk) 04:00, 22 June 2010 (UTC)

Yes, I would like to know the order, genus, or, preferably the species. --The High Fin Sperm Whale 04:03, 22 June 2010 (UTC)

Have you tried at Wikipedia:WikiProject_Fishes#Related_WikiProjects eg fishes, biology or tree of life.87.102.66.101 (talk) 12:52, 22 June 2010 (UTC)

One would almost certainly have to know the location / geological formation from which the fossil came to assign it to a particular genus or species. Do you have that information? Deor (talk) 15:03, 22 June 2010 (UTC)

I'm afraid not. I guess this is hopeless then. --The High Fin Sperm Whale 16:39, 22 June 2010 (UTC)

It's similar to a knightia alta, such as this one [1]. Mikenorton (talk) 18:13, 22 June 2010 (UTC)

Geophysics survey

Following up on the question about "Faraday cage from water": Would the electromagnetic sensors used for geophysical surveying (such as ground-penetrating radar, or induction-based electromagnetic sensors) be useful for detecting magnetic/conductive materials (e.g. iron ore deposits, manganese nodules, or the occasional Electra 10-E) underwater? 67.170.215.166 (talk) 03:55, 22 June 2010 (UTC)

Perhaps in freshwater, but I think it is unlikely to work at sea. I imagine some advanced form of sonar would be necessary for the latter. TheGoodLocust (talk) 07:08, 22 June 2010 (UTC)

read magnetotellurics which can detect material of different conductivities in the earth. Careful measurement of the magnetic field with Aeromagnetic surveys can reveal iron ore deposit below water, but it would not be economical to mine. Your ground penetrating radar would suffer too much attenuation in water to be useful. Graeme Bartlett (talk) 10:59, 22 June 2010 (UTC)

Specifically Controlled source electro-magnetic or CSEM is being used to identify the presence of relatively resistive hydrocarbons in hydrocarbon exploration offshore. Most potential reservoir rocks contain brine, which is low resistivity, except where the pores are filled with oil or gas when they become much more resistive causing an anomaly on the CSEM data. The technique is still somewhat experimental - identifying that depth at which the anomaly is located remains problematic AFAIK. Ground penetrating radar has almost no penetration into low-resistivity materials and even under the best conditions can only penetrate a few 10s of metres. Mikenorton (talk) 17:56, 22 June 2010 (UTC)

Yes, I was wondering when I wrote that if magnetic measurement could do such a thing but it seemed a bit iffy to me and I wasn't sure how well it'd work on some metals. That's why I thought sonar, specifically ultra-high frequency sonar (which might limit the range?) for its penetrating effects, would be more useful since I imagine veins of various materials would have fairly distinct sounds. TheGoodLocust (talk) 21:56, 22 June 2010 (UTC)

Seismic reflection surveys are the main geophysical tool used in hydrocarbon exploration. They're also used to in coal mines and deep gold mines. All you need is a significant contrast in acoustic impedance and you should be able to image it. The frequencies used are generally rather low - 20–40 Hz is pretty normal although special kinds of acquisition can get up to 1000 Hz, but such high frequencies are attenuated very quickly in the earth and so the depth of penetration is limited. Mikenorton (talk) 22:09, 22 June 2010 (UTC)

The OP has asked for solutions to different problems. Metal ores, mineral deposits, and hydrocarbon reservoirs occur (usually) deep below the seafloor. A crashed airplane or a sunken ship should be near the seafloor - depending on the depth of water, there will be minimal to severe buildup of new sediments. But, there will still be a "bump" on the sea floor. When searching for Titanic, the crew from WHOI used a side-scan sonar to detect a "bump". But, Titanic was on the bare edge of detectability (many years ago - presumably the resolution has improved with new technology). In any case, it's not likely that a small aircraft would be detectable at great depths by any technology currently available. On the other hand, streamer-based seismic reflection surveys operate at very low frequencies (as low as even 5 Hz, and up to ~40 Hz as Mike Norton pointed out). These surveys can operate in much deeper water; but they are specifically intended to survey the deep subsurface (below the seafloor). At such frequencies, it would be very unlikely to detect a small bump on the seabed due to a ship, aircraft, or other anomaly on the surface. After significant post-processing and analysis, you might be able to discern a surface static, but that could be due to anything - geological anomaly, rocks on the seafloor, variations in the bathymetry, even choppy water at the sea surface. Nimur (talk) 15:46, 23 June 2010 (UTC)

Site surveys for locating exploration wells offshore use a mixture of high-frequency seismic reflection and side-scan sonar data. This is is intended to look out for any obstructions on the seafloor at the proposed well location that might get in the way of the rig - such as shipwrecks. This data of course is only acquired in a small area around the proposed location, you couldn't do it over large areas. Mikenorton (talk) 18:01, 23 June 2010 (UTC)

Potato battery

A recently published article has been making the rounds on the Internet lately, with bold claims of "The treated potato battery generates energy that is five to 50 times cheaper than commercially available batteries". But reading the study I did some calculations and with the 225cm² of Zn surface area in their potato cell at ~1.2mWh/cm² (their data) the total power capacity of their potato cell is only 270mWh, less than half of the most basic Zinc-Carbon AA battery, yet they proclaimed "at maximal performance the treated Zn/Cu-potato cell is markedly more economical than a typical 1.5 V AA alkaline or D batteries." Is my calculation correct? Can anyone decipher how they arrived at the cost analysis and conclusion? Is this article (at least its claims) completely hogwash? --antilived^{T | C | G} 06:50, 22 June 2010 (UTC)

I think the idea is that you have more than one cell, and their combined cost is lower than a regular battery. That said, the idea is nonsense anyway. There were people talking about how much potatoes cost, and sorts of other nonsense. The power comes from the metal. NOT the potato. The potato does nothing. Just replace it with some salt water. Ariel. (talk) 06:53, 22 June 2010 (UTC)

You'd have to pay for the metal rods and wires and cost your time too. By the way can I interest you in some stone soup?, a couple of potatoes now would give it some body. Dmcq (talk) 10:29, 22 June 2010 (UTC)

50 times cheaper - I cannot disagree with this claim - the cost of the battery is that of the metal plates they are using, plus the boiled potato - compare with convention batteries - they don't just use zinc plate - but specially prepared zn powder, plus MnO2, plus construction costs - to what is a quite sophisticated finished product - the potato battery just uses the raw materials - it will without doubt be much cheaper. I don't know if they've included transportation costs...

They also compare against $1.89 AA batterys - not only is this overpriced, but a poor comparison - D cells are much cheaper per Joule. —Preceding unsigned comment added by 87.102.66.101 (talk) 15:41, 22 June 2010 (UTC)

Second claim more economical - no idea what 'economical' means in this context - probably a repeat of the above correct claim.

Summary: Not hogwash (but getting close) - but not actually a practiable energy source. (see below)

Note: This battery would be fine for a digital watch, but I'm fairly certain that it would have serious problems driving a substantial load - eg radio loudspeaker, or even tiny electric motor. A led is not a demanding load. They tested at loads of less than 0.01Amp Otherwise it's interesting to note the suitability of boiled plant matter as a ion conudctive material.87.102.66.101 (talk) 13:11, 22 June 2010 (UTC)

monofilament cutting string

In SciFi stories sometimes they have monofilament strings that are just one atom wide and can cut through anything. But wouldn't the material that was cut just immediately vacuum weld back together again? (You don't get a better vacuum than that, and the cut piece are exactly in the right spot to join right back together.) I'm guessing metals would do that? But would more complicated molecules? Say a piece of wood? Would it depend on what kind of bond the molecule used? Ariel. (talk) 07:12, 22 June 2010 (UTC)

Yes, this idea pops up in Sci-Fi books/comics/manga/anime/movies/cartoons a lot; see this partial (but very impressive) list. A "monofilament" (a molecule, really) one atom thick makes no sense, however, as it has a strength of a single molecule. The work needed to tear it is about the same as the work required to move a couple of electrons from one orbital to another, that is, something of order of 10^-18 Joule. So no, that won't cut anything. If you take a bunch of, say, nylon molecules side by side, however, then you have a fishing line. The thicker it is, the stronger it is. And yes, you can get some nasty cuts from the fishing line if you are not careful. --Dr Dima (talk) 08:24, 22 June 2010 (UTC)

I'd imagine having such low mass would be a major hindrance as well. If one could increase the strength of the electromagnetic force in the filament then that should get rid of the strength issues (it is sci fi after all), but that would still leave the mass problem, which I suppose could be countered by increasing the acceleration of the weapon. TheGoodLocust (talk) 08:37, 22 June 2010 (UTC)

Yes, you can do that, but the cutting implement will not be a monofilament string anymore; rather, it would be an ion beam. Yes, an ion beam can cut solid materials. --Dr Dima (talk) 08:52, 22 June 2010 (UTC)

Why would it be an ion "beam"? I'm saying increase the electromagnetic force to increase the strength of the molecular bonds, sure you could do that with ions, but would that have to be a beam? TheGoodLocust (talk) 21:39, 22 June 2010 (UTC)

By the way, if we return to the original idea of a very thin monofilament string, you can see that it is unlikely to work by doing a simple dimensional analysis. Note that, for a given force applied to the filament, the pressure it exerts on the surface you are trying to cut is proportional to the force applied to the filament divided by the filament diameter to the first power. However, the maximal force the filament can withstand is roughly proportional to its cross-section, so to its diameter squared. Assuming you pull on the filament with the maximal force it allows without breaking, then, for the same cutting configuration, the pressure will increase as the first power of the diameter. That is, the larger is the filament diameter the higher is the pressure it exerts on the surface you are trying to cut. Indeed, I've never heard of anyone getting cut by walking into a spiderweb; but a snapping steel cable will cut a person clean in two. --Dr Dima (talk) 09:04, 22 June 2010 (UTC)

...and to finish that thought: Spider's web is gram-for-gram stronger than steel...so if the idea of thinner (being "sharper") is better - then spiders web ought to cut more easily than a cheese wire - which in turn ought to cut better than a steel cable. SteveBaker (talk) 10:24, 22 June 2010 (UTC)

In the stories the monofilaments are made of unobtainium. So assuming they are strong enough - what about the vacuum weld part of my question? Would molecules reconnect? Ariel. (talk) 03:21, 23 June 2010 (UTC)

Sounds feasible, but I guess you don't know until you try. If it is a problem then perhaps heating the monofilament, causing evaporation as it cut, would solve such a problem - the only problem with that is that it would have to be pretty hot and good at conducting heat to work since it'd have such a small contact area. In this imagining it'd essentially be a strong and flexible heating element - and would probably look a lot cooler than a simple monofilament. TheGoodLocust (talk) 06:52, 23 June 2010 (UTC)

If you've removed molecules with the (abrasive?) monofilament then there's a gap -a gap remains a gap even at 1 atom wide.77.86.123.157 (talk) 12:57, 23 June 2010 (UTC)

Again, it is more complicated than that. Some of the molecules (proteins, genetic material, structural elements of the cell wall) in the living cells are fairly large. If they get cut or dislocated, some of them may reconnect (see e.g. our very extensive article on DNA repair), and some may not; especially unlikely to reconnect are the structure elements under tensile stress. If the damage is extensive, the cell will go into necrosis or apoptosis. Perforation of the cell wall alone is usually a good enough reason for a cell to promptly die. So no, the cell will not necessarily repair itself, but there will not be a 1-atom gap left, either. Here is a good example: when you stick a glass microelectrode in a nerve cell, and you are careful enough, the membrane seals itself around the electrode and the cell keeps functioning, at least for a few hours. If you are not careful enough, and the membrane damage is too big, the cell dies within seconds. --Dr Dima (talk) 22:11, 23 June 2010 (UTC)

Inner asteroid belt?

Is there any reason there is no asteroid belt within the Mars, Earth, Venus, Mercury and the Sun? Just chance, or some does physical principal exclude this possibility?80.1.88.13 (talk) 08:00, 22 June 2010 (UTC)[Trevor Loughlin]

Well, I'm totally guessing here since I've never taken any astronomy classes, but I'd imagine that as matter accretes into planets they'll move closer to the sun. Once this happens I think the complex gravitational interactions between the planets, sun, and asteroids would tend to throw the remaining asteroids in the core of the system into each other to make more planets, into the existing planets to increase their mass or into the sun. The outer asteroid belt wouldn't be subject to such chaotic gravitational forces as frequently and should remain relatively stable. TheGoodLocust (talk) 08:32, 22 June 2010 (UTC)

Jupiter perturbs orbits and makes planet-formation difficult. Being further away allows the asteroids to accrete into planets. So implies our Asteroid_belt#Origin article, anyway. Vimescarrot (talk) 10:36, 22 June 2010 (UTC)

In this close the planets will muck up the orbits and make them unstable, even though Mars etc are smaller, they would be much closer to an inner belt and have a huge impact. Graeme Bartlett (talk) 10:54, 22 June 2010 (UTC)

There are small groups of asteriods in these regions: Atens, Apoheles, etc. (See also List of minor planet groups.) There are no known Vulcanoids, whose orbit would be between Mercury and the Sun, though. 75.41.110.200 (talk) 17:08, 22 June 2010 (UTC)

As far as I know, one of the most accepted theories of the formation of the asteroid belt is that the huge mass of Jupiter stopped them to form a planet (or destroyed the emerging new planet via its tidal forces). The other planets are just not big enough to do this. --131.188.3.21 (talk) 01:19, 23 June 2010 (UTC)

Ferrofluid heart assist jacket?

Some researchers have created experimental powered jackets surrounding the heart to give about 10% assistance in the case of heart failure. Could the power limitations be overcome by using a ferrofluid filled jacket (surrounding the heart, as before) powered by superconducting magnets external to the patients body?[Trevor Loughlin]80.1.88.13 (talk) 08:20, 22 June 2010 (UTC)

I can't comment on the physics, but I doubt the FDA would approve such a device with that kind of liquid in it. Perhaps someone qualified can comment on the FDA's views on the chemicals used in ferrofluids.--mboverload@ 09:28, 22 June 2010 (UTC)

Ferrofluids tend to be things like oil or water with nano-scale particle of iron, magnetite or hematite suspended in it. Certainly stuff like that would be pretty disasterous to have inside your body if the surrounding container leaked. I think the toughest problem would be to find a material flexible enough to pump the heart millions of times without breaking - that is also biologically tolerated. For a short-term emergency, it ought to be OK - but not for long-term use. SteveBaker (talk) 10:17, 22 June 2010 (UTC)

A superconducting electromagnet has significant size, weight and power consumption. Besides its non-portability it raises safety issues, see MRI#Safety, and it would be unacceptable for a patient with a medical implant such as a pacemaker. Cuddlyable3 (talk) 10:31, 22 June 2010 (UTC)

If I had tubes of magnetic fluid wrapped around my heart I don't think I'd want to go anywhere near a superconducting magnets. APL (talk) 15:21, 22 June 2010 (UTC)

Metal mesh interfere with WiFi signal?

Could a laptop stand fashioned from this mesh interfere with the laptop's WiFi signal? --89.243.136.23 (talk) 09:35, 22 June 2010 (UTC)

If it is just a stand it won't have much effect, but if the mesh blocks the line of sight to the wireless router it could well seriously degrade the signal. Graeme Bartlett (talk) 10:50, 22 June 2010 (UTC)

power electronics

what's the difference between a volotage regulator and voltage stabilizer? —Preceding unsigned comment added by K.saikishan (talk • contribs) 10:53, 22 June 2010 (UTC)

A voltage stabilizer appears to be the name of a finished product (ie a box with inputs and outputs). A voltage regulator is a more general term which can refer to a single component, integrated chip, or finished product.87.102.66.101 (talk) 13:15, 22 June 2010 (UTC)

See Voltage regulator and Voltage regulator#DC voltage stabilizers. The article does not make a consistent distinction between voltage regulator and voltage stabiliser. For me a voltage stabiliser uses a non-linear component in parallel with the load to conduct i.e. waste current as required to prevent the voltage exceeding a specified voltage, while a voltage regulator has a more complex circuit with feedback that employs a voltage reference separate from the load. Cuddlyable3 (talk) 22:05, 22 June 2010 (UTC)

The term voltage stabilizer usually applies to an ac source, whereas voltage regulator usually applies to control of a dc source.--RampantHomo (talk) 21:03, 27 June 2010 (UTC)

Cheetah attacks

Have there ever been any reports of Cheetahs attacking humans? Your article on the Cheetah doesn't give any details on this. 202.129.232.194 (talk) 13:41, 22 June 2010 (UTC)

Yes http://www.google.co.uk/search?hl=en&q=cheetah+human+attack&meta= eg [2] [3]

87.102.66.101 (talk) 15:20, 22 June 2010 (UTC)

saltation velocity vs choking velocity

What is the rough numerical difference between choking velocity and saltation velocity for fine particles? How reliable is the rizk correlation for saltation velocity compared to the equation: slip velocity at saltation=terminal velocity? Can anyone suggest an accurate correlation for particle velocity? Thanks —Preceding unsigned comment added by 122.172.201.6 (talk) 15:36, 22 June 2010 (UTC)

First question. Try [4] p4.12

This book also has numerous models for both which might be useful to you [5] 87.102.66.101 (talk) 15:53, 22 June 2010 (UTC)

Dense phase flow vs dilute phase flow

In pneumatic conveying which uses more power, dense phase flow or dilute phase flow? Thanks —Preceding unsigned comment added by 122.172.201.6 (talk) 15:40, 22 June 2010 (UTC)

Petroleum detergent in Dawn

There was an NPR story[6] this morning about the use of Dawn dish detergent in the BP oil spill. The story mentioned that Dawn contains a petroleum product itself and alluded that is why it works so well. Any idea what type of compound that would be? --70.167.58.6 (talk) 15:52, 22 June 2010 (UTC)

A lot of surfactants are made from alkanes and paraffins as chemical feedstocks. It's like saying hydrochloric acid is water-based and that's why it works so well. John Riemann Soong (talk) 16:00, 22 June 2010 (UTC)

They mentioned that Dawn was composed of about 1/7th petroleum ingredients. One of the theses in the story was that Dawn was "eating it's own tail" by being a super-cleaner used to combat a spill of the very parent material it's derived from. They brought up the fact that petroleum-free soaps do exist but are ignored by anyone on cleanup duty because they lack effectiveness. The other telling part of the story was that the cleanup process for marine life is actually kicked off by coating them in cooking oil, as a way to displace the crude oil that's grown very thick and sticky from it's time in the sun. Seems to me that the basic premise behind Dawn is that it's so effective because it can totally displace so many other oils, and rinses away completely when diluted. Interesting, all around. --144.191.148.3 (talk) 16:27, 22 June 2010 (UTC)

Depending on the type of 'dawn' [7] ? The active ingrediants are/will be anionic surfactants and non-ionic surfactants msds There's a list at Surfactant#Classification

Without knowing 'dawn' (I assume it's similar or near identical to Fairy Liquid) [8] likely major constituents are Sodium lauryl sulfate, Sodium laureth sulfate. The non-ionic components include Lauramine oxide [9] , C9-11 pareth-8 link shows C12 version 1,3-Cyclohexanedimethanamine [10] , polypropylene glycols and Dimethyl aminoethyl methacrylate/hydroxyproplyl acrylate copolymer citrate , which are also detergents/surfactants/dispersants and reduce the harshness of the formulation in terms of degreasing of hands etc.

All of these will contribute to its activity.87.102.66.101 (talk) 16:23, 22 June 2010 (UTC)

There must be something special about "Dawn" as opposed to other brands of washing up liquid. It's common for particular applications to specify Dawn in particular...for example, when I put vinyl rally stripes on my car, the instructions were very specific that the area where the decals were to be applied had to be washed with water with a few drops of "unscented Dawn" - and NOT any other brand. I also had some rubber grommets to fit into a row of tight holes through which electrical wiring has to be threaded - and again, the instructions were to lubricate the grommets with "Dawn". I suspect (without proof) that Dawn has very little in the way of non-detergent stuff in it so it's more pure than the stuff that's usually sold with hand softeners, scents and who-knows-what other junk in them. SteveBaker (talk) 19:35, 22 June 2010 (UTC)

Isn't it just another fuzzy example of a Genericized trademark? I'm even going to go crazy and say that there is no such thing as 'unscented dawn' as a product .. what they mean is 'plain normal dawn'. 87.102.66.101 (talk) 21:07, 22 June 2010 (UTC)

Dawn (brand) and Fairy (brand) are both brands owned by Procter & Gamble. Here is video documentation] of the former compound's ability to maintain the resilence of an adult female's epidermis during culinary utensil cleansing duties. Cuddlyable3 (talk) 21:38, 22 June 2010 (UTC)

I'm more interested in SteveBakers admission "..when I put vinyl rally stripes on my car.." - was that a long time ago steve? 1970's much ? 87.102.66.101 (talk) 22:01, 22 June 2010 (UTC)

Once a year ago (white stripes on my British Racing Green '63 Mini), then 2 years ago (black stripes on my Orange MINI Cooper'S convertible) then 3 years ago (white stripes in my British Racing Green MINI Cooper'S)...between those, my Yellow MINI got crushed before I had time to put the (Black) stripes on it - and my present Red MINI came with stripes from the factory. MINI's just look good with stripes...other kinds of cars...not so much. Evidence: [11], [12], [13], [14] SteveBaker (talk) 23:40, 22 June 2010 (UTC)

Sorry to here about your yellow mini - we used to have one of those .. long time ago..87.102.66.101 (talk) 23:46, 22 June 2010 (UTC)

I heard the NPR story, and as I recall, the reason for the use in cleanup is that it's a strong detergent which is able to break up oil, but will not unduly strip oils from hands and skin. This was attributed to the particular *mix* of surfactants used by Dawn. (Online lists include sodium lauryl sulfate, sodium pareth-23, sulfate C-12-14-16, dimethyl amine oxide, undeceth-9, cyclohexandiamine, and polyacetate. P&G somewhat reasonablly keeps the exact formula secret.) -- 174.24.195.56 (talk) 05:05, 23 June 2010 (UTC)

Clarify - All liquid hand washing detergents are formulated to not unduly strip oils from hands and skin - not doing so would result in tens or thousands of people suing the producer for induced dermatitous or similar. The ingrediants in dawn/fairy liquid are commmon to all liquid hand washing detergents. One of dawn/fairy's main selling points is the higher concentration they use - "more dishes per bottle" - Their formulation is a good one (and probably the original and best, from which others copy), but any innate advantage isn't there - that's all due to the millions Procter and Gamble spend on advertising and marketting every year - the rival products are so similar - the only way to differentiate is consumer awareness.77.86.123.157 (talk) 13:05, 23 June 2010 (UTC)

You'll find similar brand loyalty for "Ludwig" in Poland, and for "Pril" in Germany. The article http://de.wikipedia.org/wiki/Pril is interesting in it's description of an early advert for Pril.77.86.123.157 (talk) 13:42, 23 June 2010 (UTC)

arent surfactants toxic to fish ?

any way to get plant cells to grow along a surface?

Plant cells with intact plasmodesmata behave a little differently than protoplasts....anyone have a technique for culturing cells only at max a few cells thick on a microscope slide? John Riemann Soong (talk) 15:59, 22 June 2010 (UTC)

well here's what I roughly have in mind -- I'll take a sample from an explant, sonicate it in some solution to make a suspension culture; then add it to an polylysine-treated slide and let the slide incubate.

I'm thinking if I control the incubation time, the plant cells will grow along the surface than against gravity. (Okay someone help me -- I don't know that much about plant cell division.) I was thinking that if I even control the culture medium I leave on the slide as it incubates, I could get a thin layer rather than a thick callus. I'm thinking that if I leave part of the slide barely immersed, even if the medium evaporates the cells can still pull water through the plasmodesmata; the strong osmotic forces might even help the gold particles I will eventually insert on the liquid-rich side travel faster? John Riemann Soong (talk) 16:32, 22 June 2010 (UTC)

Can't answer your specific questions but how about using the skin found between layers of onions - it is already one cell thick. 86.7.19.159 (talk) 23:58, 24 June 2010 (UTC)

terminal velocity of flour?

Hi Can anyone tell me what the terminal velocity of flour is? Thanks —Preceding unsigned comment added by 122.172.201.6 (talk) 16:04, 22 June 2010 (UTC)

Loose flour? I suspect it is going to depend on how finely it is ground. Googlemeister (talk) 16:31, 22 June 2010 (UTC)

Wheat flour having a rough particle size of a little over 0.1mm —Preceding unsigned comment added by 122.172.201.6 (talk) 16:48, 22 June 2010 (UTC)

I don't think it's meaningfull to talk about the terminal velocity of such small particles. They will be suspended in the air for a long time before settling. That isn't because they are falling very slowly, it's because they are moving around randomly (see Brownian motion). We considering terminal velocity, we don't think about individual molecules of air, we average them all out because there are so many hitting the falling object. For a single particle of flour, though, there aren't many molecules hitting it (well, there's probably still a big number by every day standards, but it's a small number relatively speaking) so we can't ignore the fact that they are all moving around at random. The particle will be pushed in different directions by different molecules, which makes its movement unpredictable. --Tango (talk) 17:04, 22 June 2010 (UTC)

There is an equation at Terminal_velocity to use to calculate it. You can use the density of flour and an assumption of light packing to calculate the mass of a 0.1mm flour object.87.102.66.101 (talk) 17:14, 22 June 2010 (UTC)

Tango, two problems. A) 0.1 mm isn't very small. From the spherical approximations in terminal velocity you can estimate a velocity of order 1 m/s. For very fine particles, the second equation in Stoke's Law actually gives a better estimate of the settling velocity. At this particle size however, it also predicts ~1 m/s. B) Brownian motion in air (as opposed to water) is almost always overshadowed by turbulent motion. You'd need an exceptionally still volume of air to be able to appreciate Brownian diffusion, rather than eddy diffusion. You're right that other effects can become important when the particles are small enough, but the natural scale for observing solids suspended in air is ~1-10 microns rather than the 100 microns in this question. Dragons flight (talk) 17:42, 22 June 2010 (UTC)

Well, I don't know the maths of it, but I've spilt flour before and it doesn't fall at a steady rate. It gets suspended in air and gets blown around randomly. (You are right that the motion is more turbulent than Brownian, I apologise for that mistake.) --Tango (talk) 17:59, 22 June 2010 (UTC)

Judging from the questioneer's previous I think they're looking at transportation of fine powders using air blowers. eg Conveyor_system#Pneumatic_Conveyor_Systems 87.102.66.101 (talk) 18:10, 22 June 2010 (UTC)

I hope the OP is aware that transporting fine combustible powder suspended in air is a recipe for a disaster. See Dust explosion. --Dr Dima (talk) 19:30, 22 June 2010 (UTC)

Thanks a lot guys. I was hoping for some experimental confirmation of the equations... as the above includes a drag coefficient which again depends on some correlation. Anyway I was also expecting a velocity of around 1 m/s so this confirms my calculations in a way. Thanks. —Preceding unsigned comment added by 122.166.161.184 (talk) 04:15, 23 June 2010 (UTC)

I am sure that you will get a mixture of sizes and a variety of speeds. The dust you see suspended in the air when you drop flour is likely the finer bits. Graeme Bartlett (talk) 12:07, 23 June 2010 (UTC)

Latitude

Which latitudes(geodetic or geocentric) are shown on the topographic maps of a country? —Preceding unsigned comment added by 113.199.191.33 (talk) 16:34, 22 June 2010 (UTC)

It's going to depend on the map/mapper surely - did you have a map series in mind?87.102.66.101 (talk) 16:45, 22 June 2010 (UTC)

Any accurate map from the mid-nineteenth cenury onwards will show geodetic latitudes, that is latitudes that take account of the fact that the Earth is slightly "flattened" at the poles. The difference is small, except at high latitudes where few people live or work, but, for the most accurate work, one needs to be aware that there are several different geoids and to check which one is used for the map in question. Physchim62 (talk) 19:10, 22 June 2010 (UTC)

Excuse me, but the question isn't whether you take account of the shape of the earth, it's how. Both geodetic and geocentric latitudes are well defined for any particular geoid. --Anon, 21:22 UTC, June 22, 2010.

Indeed. See Geodetic system#Geodetic versus geocentric latitude for details. If I understand it correctly, the difference is greatest around 45 degrees latitude. At the equator and the poles, they should agree. --Tango (talk) 01:34, 23 June 2010 (UTC)

RDA percentage for calories

Is there a reason that food labels (in the USA) contain % recommended daily amount for many nutrients such as fat, protein (sometimes), carbohydrates, etc, but never do they provide a percentage for calories? There is always a caveat on the label proclaiming that it is "based on a 2000 calorie diet" but then the calories are never expressed as a percentage of that basis. It would be easy to read a conspiracy into this; the manufacturers don't want you to think "oh this 350 calorie soda is 17% of what I am allowed to have all day!" but maybe there is a more rational explanation? Is the 2000 calorie diet just not meant to be taken literally? --144.191.148.3 (talk) 17:25, 22 June 2010 (UTC)

The 2000 calorie guideline is an approximation. The number of calories you need varies widely depending on your size and level of activity. The other requirements probably don't vary as much (they probably still vary by size, not so much by activity), so giving percentages for them probably makes more sense. --Tango (talk) 18:07, 22 June 2010 (UTC)

The psychology of hog drivers

You know those incredibly loud motocycles that people drive around on? Can anyone offer an explanation for why people do that? I mean, it's just plain rude, but I'm thinking that's kind of the point. In fact there's a lot of people in my community that do this even with their regular vehicles -- they rev them so hard, it's like every day is an existential crisis for them, and doing that is their only way of balancing their mental books. But I'm interested in other people's explanations. Especially anyone who actually owns and drives a noisy vehicle. What can I do to see a decline in this behaviour, besides moving towns or deafening myself? Vranak (talk) 17:34, 22 June 2010 (UTC)

It may be cruel of me to link this, but perhaps this Tom the Dancing Bug cartoon is apposite: [15] darn I can't find it on the real TtDB website-- Finlay McWalter • Talk 17:41, 22 June 2010 (UTC)

Yeah, I feel that you're on to something. Vranak (talk) 17:52, 22 June 2010 (UTC)

it's like every day is an existential crisis for them  :) Yeah. I think from their point of view they like the sound of the engine, and the ability to control it.. Give me an electric motor and power supply and I'll happily spend hours revving it from 0 to 1500rpm. For me it's relaxing for everyone else it's annoying. Buy a drill.87.102.66.101 (talk) 17:59, 22 June 2010 (UTC)

People often don't see motorcycles. Making them annoyingly loud is thought to improve safety by making them harder to miss. As for cars, well, a free-flowing exhaust can slightly improve efficiency... but I suspect some people just like the sound. Why you most frequently see this on cars that sound like chain saws, I'm not sure. I suspect they think the exhaust sends a message saying "look at me, my car is fast".. altho, if you're driving fast, the LAST thing you want is for people to notice this. I prefer going fast in a way less likely to draw law enforcement attention. Friday (talk) 18:21, 22 June 2010 (UTC)

You need to have a passion for cars, bikes or engines in general to appreciate it. Your comment about "existential crisis" is way off the mark, it's simple enjoyment. Me? I love the sound of a Honda S2000 screaming to 9,000 rpm in 3rd gear, especially when overtaking trucks or driving through a tunnel ;) Zunaid 20:28, 22 June 2010 (UTC)

Ok, fair enough. Let me approach this from a different angle then. Do hog drivers get off on the fact that their engine noise bothers everybody else? Because I find it intolerable, and it in fact puts thoughts into my head about acquiring a Glock to take matters into my own hands. Our local government periodically talks about making such noise illegal, but all they ever do is talk. Vranak (talk) 20:40, 22 June 2010 (UTC)

Well that could be because it is very difficult and costly to enforce such issues. Googlemeister (talk) 20:45, 22 June 2010 (UTC)

I'm not sure it would be. Install a few listening devices around the neighborhood to triangulate offenders, find out where they are coming from, install a few more, and find out where they live. Then execute a search warrant, run a test of the machinery to see if it falls within acceptable parameters, and if not, prosecute. I mean, we're basically talking a few microphones and a bit of software, and a bit of analysis. It's no great feat. I wonder if perhaps we let these guys get away with it because if they couldn't express their hatred of the world that way, they'd be committing even worse crimes. Vranak (talk) 20:56, 22 June 2010 (UTC)

Riders ride for a wide range of different reasons, I used to have a 100 mile commute each way and riding it was far quicker and more fun than driving it. Born Agains and wunday riders have their own reasons, but largely people ride because it's a huge amount of fun. I suspect that you'd find that most really don't give too much of a flying f**k what other people think.

All that said there isn't the same culture here in the UK around bikes, most riders are on sports bikes, sports tourers or big trailies. There are a lot of tarts handbag riders, but proportionately far fewer than elsewhere.

There is a noise limit in the UK, and janitors can, and do, enforce it. Stopping a rider is a judgement call, and the bike is taken into the workshop to have the noise output assessed. There are practical reasons for that, largely around emissions regulation.

Riders don't hate people, although we do tend to get very p!ssed off with cagers and their SMIDSY approach to road safety.

ALR (talk) 21:11, 22 June 2010 (UTC)

Yeah, this is exactly my point of contention -- people not giving a flying fig what people think. I mean, the general rule is that if you piss people off, then you live in a community of pissed off people, which is fun for no-one, right? It just seems so short-sighted. Make a loud horrible noise and make the whole world around you a little angrier. But maybe these guys, at least where I live, are angry to begin with and so want to bring everyone else down to their level. I really wish there were a more palatable explanation but this seems to be what I arrive at again and again. Vranak (talk) 02:50, 23 June 2010 (UTC)

I think you missed my point. It's highly unlikely that anyone is doing it with the intention of p!ssing you, or anyone else, off. It's just not worth it, there are more important things to concern oneself with.

Anyway, the sound does depend on the engine type. A single cylinder has a wonderfully antiquated thump, hence thumper, I'm not keen on twins, triples make a wonderful singing sound as they rev, four cylinders and it starts getting a little anonymous.

In practice engine efficiency is quite badly affected by opening up the baffles as it reduces the backpressure on the cylinders. So it's counterproductive to mess around with them.

ALR (talk) 08:09, 23 June 2010 (UTC)

Perhaps it makes Conspicuous consumption more conspicuous? Perhaps they're worried that if they had a proper muffler some people might tragically not notice how awesome, manly, and American-made their bikes are. APL (talk) 21:26, 22 June 2010 (UTC)

More importantly, there is a significant issue of noise pollution here. Although it is annoying to encounter these sounds during the day, hearing them before eight in the morning and after nine at night can interfere with sleep patterns. I think the effects of noise pollution are considerable and may have a role to play in human health. What is so interesting (and sad) about this, is that in many cities and urban areas, people live in and swim through an ocean of noise from the moment they wake until they sleep again at night. Viriditas (talk) 22:17, 27 June 2010 (UTC)

Absorption of sugars and carbs

does the rate of how long the sugars and carbs are absorbed effect your blood sugar level? For example if I took a pill with a piece of chocolate cake and that pill slowed the absorption up to seven hours for the carbs and sugar of that cake to be absorbed, would the same number of sugar and carbs be absorbed if I hadn't taken that pill? Would your blood sugar spike more if the sugars and carbs were instantly absorbed rather than more slowly over a longer time period? How does that work? —Preceding unsigned comment added by 71.137.241.251 (talk) 18:23, 22 June 2010 (UTC)

For the record, carbohydrates are sugars. I can't answer your question, though, sorry! Regards, --—Cyclonenim | Chat  20:37, 22 June 2010 (UTC)

Your citation is invalid. I can't find that anywhere in Regards going all the way back to 1932. 71.100.2.16 (talk) 15:06, 27 June 2010 (UTC)

I think you mean, sugars are carbohydrates, not the reverse. For example, starch is a carbohydrate, but not a sugar. --Trovatore (talk) 08:17, 27 June 2010 (UTC)

Eating chocolate cake would indeed spike your blood sugar. Bodybuilders and some diets promote the concept of eating low [GI] foods and other techniques to avoid blood sugar spikes, which also lead to spikes in insulin, may lead to diabetes and will cause food cravings later on. To answer the first part of your question, if you had a pill which slowed the absorption of the chocolate cake then theoretically you might get more calories from the same amount of food. This is less clear with regards to something as easily digestable as chocolate cake, but with something like meat if you eat a massive amount of food all at once your body won't digest it as efficiently and you'll get less calories. In general, as I said, it is better to keep blood sugar at stable levels by avoiding simple sugars, eating fiber with your meals to slow digestion, and, on a related subject, mixing proteins (e.g. casein, egg, etc), which digest at different rates, will provide your body with a constant stream of amino acids necessary for maintaining and building muscle. TheGoodLocust (talk) 21:29, 22 June 2010 (UTC)

what is a "thin cell layer explant"? (TCL)

People in the literature keep talking about this technique (with some modifications) as some promising way for growing whole plants... which is not what I want. I just need to observe a layer of plant cells (with plasmodesmata intact) under a DIC microscope! Can someon help me find a protocol just how to MAKE a TCL culture, straight up? John Riemann Soong (talk) 19:14, 22 June 2010 (UTC)

Well, here is a recent review of the technology and its applications, for what it's worth. Looie496 (talk) 22:26, 22 June 2010 (UTC)

Wait I think I read that one already...John Riemann Soong (talk) 22:41, 22 June 2010 (UTC)

human brain and language

Is it possible for a person through brain trauma to completely forget their own language and have it replaced with a different one? I am not talking about foreign accent syndrome, but actual language change. Even incomplete would be of interest, perhaps a single word is always replaced with a foreign word? Like an English speaker who lost the ability to express the word "air", even in thought, and it came out as the German word "Luft" instead? Or perhaps they completely forget English and are unable to relearn it, but are able to learn German as a substitute? Googlemeister (talk) 19:28, 22 June 2010 (UTC)

You can't suddenly learn a language you didn't previously know following a bump on the head, if that's what you mean. I believe there are forms of aphasia (that's the article to read for everything on this subject) where you might sound like you are speaking another language, but it is actually nonsense. I believe there are also conditions where patients revert to their mother tongue and lose the ability to speak foreign languages they had previously known. I'm not aware of any condition where you can learn a new language but not relearn a previously known one, nor can I see how that could occur. --Tango (talk) 19:37, 22 June 2010 (UTC)

I don't think OP means that the person would suddenly start speaking another language, but instead have the person replace certain words of say English with other languages that they know (for example I know hello in English and bonjour in French). Could that happen? Regards, --—Cyclonenim | Chat  20:35, 22 June 2010 (UTC)

That is quite common, even without any sort of brain injury! As a "serial ex-pat", I've seen it many times; when I used to live in France, it was not uncommon for me to switch unconsciously from English to French while talking to my parents on the phone. Physchim62 (talk) 22:37, 22 June 2010 (UTC)

The "incomplete" type definitely occurs -- "pathological mixing" is a common result of bilingual aphasia. It is also possible for the native language to be more seriously impaired than the second language. I couldn't find any mention of cases where the native language is completely lost and the second language remains fully intact, though. Search Google Scholar or Pubmed for "bilingual aphasia" if you want to get into the literature on this topic. Looie496 (talk) 21:42, 22 June 2010 (UTC)

See the article Glossolalia. Cuddlyable3 (talk) 22:22, 22 June 2010 (UTC)

Glossolalia usually involves the person speaking in a previously known, unknown (by the speaker) or "holy language", but any inability of the speaker to use their own language would be temporary. ~AH1^(TCU) 15:19, 23 June 2010 (UTC)

Fiber Optic Duplex Communication

Can an optical fiber carry optical information in opposite directions at the same time when both light beams are the same frequency or will they interfere?--74.67.89.61 (talk) 20:12, 22 June 2010 (UTC)

Yes. One needs an optical directional coupler or "hybrid" at each end to separate the forward and reverse signals. Cuddlyable3 (talk) 22:18, 22 June 2010 (UTC)

An Optical circulator can do the job. They work at a specific wavelength such at 1550 nm. Alternatively you can have different wavelengths going in each direction. Graeme Bartlett (talk) 10:55, 23 June 2010 (UTC)

So full duplex communication along one optical fiber with the same wavelenght is possible, you just need special equiptment to seperate the signals from any reflections? —Preceding unsigned comment added by 74.67.89.61 (talk) 14:08, 23 June 2010 (UTC)

Asked and answered. Cuddlyable3 (talk) 13:07, 24 June 2010 (UTC)

culturing pollen tubes

Are pollen tubes capillaries of many cells or just a single cell? The article says that sperm cells are carried in them....so cells get carried within a single cell?

I am thinking of culturing some pollen grains....it may be promising to have them germinate long shoots along a microscope slide (treated with polylysine if necessary to help the cells "stick" to the slide).

Also how far back the plant lineage are plasmodesmata present? Are they present in bryophytes or even plants' algae ancestors? John Riemann Soong (talk) 22:26, 22 June 2010 (UTC)

Plasmodesma says: "Species that have plasmodesmata include members of the Charophyceae, Charales and Coleochaetales (which are all algae), as well as all embryophytes, better known as land plants". Pollen tube says they are a single cell, from what I understand, the pollen grain germinates forming the pollen tube and this allows the two sperm cells to move down to the ovary and fertilise the egg. So yes, two sperm cells are transported inside another cell. You must need to use something to initiate pollen grain germination - otherwise they would germinate if they got wet which doesn't happen. 86.7.19.159 (talk) 16:03, 23 June 2010 (UTC)

Does sulfuric acid ignite matches?

I think so but I haven't actually tried it. Any other common chemicals that would ignite matches without setting off gasoline? TheGoodLocust (talk) 23:40, 22 June 2010 (UTC)

yes I believe so - the explanation is that strong acid converts Potassium chlorate to HClO₄/Cl₂O₇ (both very unstable)

Quote Mixtures of potassium chlorate and a fuel can be ignited by contact with sulfuric acid and this reagent should be kept away from potassium chlorate (from the wiki article) , probably other strong acids would do the same. Other compounds and elements are also very unstabel with potassium chlorate - more detail in that article.

I'm not sure about lighting the match and not setting off gasoline - usually the two are related..87.102.66.101 (talk) 23:52, 22 June 2010 (UTC)

It doesn't form perchloric acid; it forms the highly reactive chloric acid. --Chemicalinterest (talk) 10:57, 27 June 2010 (UTC)

Not necessarily, 87 IP -- sulfuric acid is indeed inert to gasoline, it's even used as a catalyst for petroleum refining. The reason it ignites matches is because of the aforementioned reaction with potassium chlorate. FWiW 67.170.215.166 (talk) 02:49, 23 June 2010 (UTC)

Que? "I'm not sure about lighting the match and not setting off gasoline" is what I said, what are you talking about?77.86.123.157 (talk) 13:08, 23 June 2010 (UTC)

Oh I see now - something that lights a match and does not ingnite gasoline.. As a cheat answer how about sandpaper, or the strips on the box that is used to light the match?77.86.123.157 (talk) 13:19, 23 June 2010 (UTC)

The point is to ignite on impact. The bottle shatters, letting out both the acid and the gas, the acid sets off the match and that ignite the gasoline. I'm also rather curious how sulfuric acid would react with some of the other things added to molotov cocktails like coal/charcoal dust, various thickening agents (e.g. egg whites) and oil/tar. I'm assuming it wouldn't react with the charcoal/oil stuff (I could be wrong), which makes me most interested in which method of gelled gasoline would be best for an impact fire grenade. TheGoodLocust (talk) 17:14, 23 June 2010 (UTC)

Can you expand on what you are talking about - your original question was about matches and sulphuric acid - now you seem to be talking about some sort of incendiary device - what is this ? 77.86.123.157 (talk) 17:36, 23 June 2010 (UTC)

I'm basically talking about a modified (easier to make and use) version of this. This device is commonly described in a lot of books, but I've never seen a description that uses matches instead of sugar/KClO3 for ignition . TheGoodLocust (talk) 20:21, 23 June 2010 (UTC)

I see. The strike anywhere match will almost certainly ignite on contact with conc sulphuric acid. The safety match might, or may not, or the combustion may be delayed or weak due to the relative lack of reactive combustable material in the head (excluding the wood of the match itself); the remainder in a safety match is sulphur - I'm not sure hwo readily it reacts with acidified chlorate - but think it won't be spontaneous. An experiment would check this.77.86.123.157 (talk) 21:11, 23 June 2010 (UTC)

Well, I think the only confounding factor is that I believe there is a coating on matches that covers up the potassium chlorate (not sure what it is). Anyway, homemade incendiary grenades are basically bottles filled with sulfuric acid and gas and (after cleaning the outside of the bottle of course) they tape/tie on cloth that is soaked in a sugar/potassium chlorate solution (going off of memory here). It just seemed like taping on matches would be a more accessible method for creating such a device and would last longer. TheGoodLocust (talk) 00:01, 23 June 2010 (UTC)

You can check out the article on Molotov cocktail for more info. Clear skies to you 67.170.215.166 (talk) 02:51, 23 June 2010 (UTC)

Yes, I hadn't looked at it, but it looks like the version I described is close to the Polish Home Army version. However, that article doesn't mention the ignition system that I'm proposing, which is to tape matches along the outside of the bottle. The match on the one in the article is supposed to be lit before throwing, which is inferior in several ways - time, environment (wind/rain), and stealth (a light storm match at night would tell people where the bomb came from, which is why impact ignition is preferable). TheGoodLocust (talk) 03:29, 23 June 2010 (UTC)

Guys perchloric acid may be very thermodynamically unstable, but it takes a lot to get it going. John Riemann Soong (talk) 16:11, 23 June 2010 (UTC)

Also as I recall, perchloric acid is a stronger acid than sulfuric acid. There is no way sulfuric acid will completely protonate perchlorate. John Riemann Soong (talk) 16:12, 23 June 2010 (UTC)

The nice thing about sulfuric acid is that anyone can get a hold of it pretty easily (concentrate it from battery acid). TheGoodLocust (talk) 17:16, 23 June 2010 (UTC)

I think concentrated sulfuric acid will ignite a matchstick — no need for the matchhead at all. But I haven't actually tried it. --Trovatore (talk) 21:13, 23 June 2010 (UTC)

I think it will just char the wood - but not burn .. in fact matchsticks are coated in paraffin/wax - which would protect it from reaction with the acid. A small piece of untreated wood would be converted roughly to carbon, but with no flames - a similar reaction to the sugar/sulphuric acid reaction (see youtube), but slower since the wood is not finely divided.77.86.123.157 (talk) 21:17, 23 June 2010 (UTC)

Well, I was thinking that I might have to scrap off the coating on the head, but I wasn't sure how difficult it would be and wouldn't want to do it if it wasn't necessary. I suppose the nice thing about soaking something in a sugar/chlorate solution is that you could take something like a bottle of Snapple brand ice-tea, soak the label in such a solution and let it dry. That'd be a nice little covert weapon. TheGoodLocust (talk) 21:52, 23 June 2010 (UTC)

Yeah, that's a good idea, but you have to be sure to use a strike-anywhere match, not a safety match -- the latter doesn't contain KClO₃ in the matchhead, only in the matchbox. Seriously, though, what do you need this info for? First you ask about extracting arsenic from microchips for use as a poison, next about igniting matches with sulfuric acid, and now this? 67.170.215.166 (talk) 01:35, 24 June 2010 (UTC)

KClO3 is in the matchbox for safety matches? The matches article says it is in the head? As for your question, I have nothing nefarious planned, but I suppose the information would be handy in a Red Dawn or V for Vendetta scenario - I just have an interest in improvised and/or stealthy weaponry. I probably should re-ask my question about how to poison someone with microchips (or if it is even feasible) since it was posted so far up. TheGoodLocust (talk) 01:54, 24 June 2010 (UTC)

Oh yeah, I must've confused the potassium chlorate with the phosphorus -- it's the phosphorus that's in the matchbox, and the chlorate is in the head (that's what makes safety matches {relatively} safe). As for the microchip question, I'll repeat what I already said: you could extract the arsenic by melting the microchip in an inert atmosphere (which would sublimate the arsenic), but the quantity of arsenic extracted in this way would be too small to be useful. Good luck with your writing :-) 67.170.215.166 (talk) 02:31, 25 June 2010 (UTC)