John Cuthber

Roughly how common is that?

There are real losses due to eddy currents. On the other hand the idea that the magnets"wear out" isn't a real problem. The worst position for a magnet to be in from the point of view of demagnetising force is next to another magnet N to N and S to S. Any combination of gears will sometimes be less strongly demagnetising than this. Think about an ordinary bar magnet- it is 2 magnets stuck together head to head and tail to tail. If you cut it carefully down the middle you get 2 magnets. Since ordinary magnets are stable for years there is evidence that these gears should work well. On the other hand, normal gears are fairly efficient anyway so, except in a few odd situations, it's probably not worth bothering. The thread's title is misleading. These are not really gears so the fact that you can't have gears without friction doesn't apply. "Something that isn't a gear does something that gears can't" isn't very eye catching. "you need to remember conversation of energy." There's nothing inconsistent with the conservation of energy with using magnetic forces to move things. A magnet has, by virtue of the field) some stored energy. For you to say this energy "goes away" is actually a breach of the conservation principle unless you can say where it goes.

Joy, Do you understand that there is a difference between "poodles are dogs" and "dogs are poodles"? Similarly, there is a difference between "liquids that acts like a solid under pressure are non newtonian" and "non newtonian liquids acts like a solid under pressure ". Since the second of these is what you said, but the first of them is true I still think you were wrong.

"Are not arrogant and inconsiderate bicyclists equally as annoying as their counterparts in cars?" No, because they don't kill other people.

I agree that you should "think before you drink"; it's darned hard to think properly afterwards. Anyway, I used to brew my own and the best advice I can give is keep everything clean. (Also don't prime bottles with too much sugar)

Breathing might be an interesting problem too.

Well, you may say "That's assuming the building doesn't have a decent ventilation system... but ours does." But there seems to be some question of the adequacy of the ventillation. "After about an hour and a half, they let us back into the building, but they turned up the vacuum system in the building, so get the fumes out and to cycle the air, I guess. The problem, is that this changed the pressure significantly in our P2 lab (for dealing with hazardous pathogens), which set of an alarm. (sigh)." Anyway, no reasonable ventillation system can keep the methanol concentration above a large spill within safe limits. Ravio, before posting this "In my humble opinion such reaction to the methanol spill was surely an overkill. Not that this kind of spill does not need attention - it surely does - but funny thing is that university with all its educated minds is not able do deal with it and so much help from other institutions is needed. " Did it occur to you that those educated minds might have a better informed humble opinion than yours and that their reaction was not overkill? Just think what one static spark could have done in the right place at the right time. Then think what you would be saying if they hadn't decided to clear the building and get the clean-up squad. Would you be saying "Well, we lost the building and a few people but since it was only a methanol spill that's OK"?

If you need to ask that sort of question please don't try working with phosphorus (red or white). The reactions are rather complex but they can be summed up as the glycerine get's oxidised by the permanganate. This reaction generates heat and the hotter the mixture gets the faster it reacts. The temperature rises rapidly until the material catches fire.

Yeah, It's just methanol. Roughly as flammable as gasoline. Burns with a near invisible flame so it's possible to walk into a methanol fire before you see it. It's got an idlh value of about 8 g /metre cubed so 4 liters ie 3.2Kg is enough to make 400 cubic metres of air unbreathable. Hey, why tell anyone to get out of the building? It is noted for its ability to be absorbed through the skin but that's no reason for the delivery bloke to remove any contaminated clothing. It sends you blind at doses less than it takes to kill you but if it's a choice between that or flashing next week's washing at passers by then hey, who wants their underwear on display. Get 6 % or so of it into the air and then you can light it too. This stuff is used to power racing cars but that's no reason to worry about it exploding in the building is it? Seriously, as far as I can see the only things that went wrong during that event were that the stuff should have been packed better and someone should have tripped the fire alarm to get everyone out. I would ask why you didn't set the alarm off ecoli, but I know that when I had an incident with a leaking hydrogen cylinder I didn't sound the alarm. People don't always think straight in emergencies. At the end of the day nobody was hurt, the emergency services might have had their day livened up a bit and your experiment went West. As you said, "Or maybe the problem is that scientists just like to complain about everything... especially when it comes down to criticizing their university amoungst themselves. "

Since AgSCN is practically insoluble you can't really do a titration with it. You can use it as part of an indicator system (in the presence of Fe). Titrating with HCl then trying to measure Cl would be ill advised- it's much easier not to add lots of the stuff you are trying to measure. There's nothing to stop you doing the titration with HNO3 to as exact an end point as you can get for the determination of the base then adding excess acid and titrating with AgNO3 to measure the chloride, again to as good an end point as you can get. Warming the solution isn't going to help a lot either.

Since many elements show multiple oxidation states the table is ambiguous. If it's meant to me highest oxidation states then copper is wrong; if it's meant to be most common then iron is wrong. If the asignment is arbitrary then it's all wrong. It also fails to convey any information about the underlying reason for the periodic nature. It springs from the arangement of the electrons in what for simplicity's sake are usually called shells.

"Believing in creationism is kind of like one scientest believing in a certain scientific threory and another one disagreeing with the theory. " Bollocks! In the end the evidence of further experiments should get the 2 scientists to agreee. That's the whole point of science. The creationists will (and do) continue to believe in their "faith" even after it has ben shown to be, at best, unreliable. Believing in fairy tales is not, directly, a bad thing. But if it leads to killing your neighbour because he eats boiled eggs blunt end first then it's very clearly a bad thing. If we stopped tollerating the myth that "it's OK to believe stuff with no evidence" then at least some of the causes of conflict in society would be addressed. Racism, for example, has just as much scientific validity as creationism. Stamp out the idea that "people should be permitted to believe rubbish if they want" and you get rid of both evils. Of course, I'm not saying that religion is the sole source of trouble in the world, just that it's one of the biggest and that most of the others (nationalism for example) are similar in that they rely on a belief (my God/ my country is better than yours) which is invalid.

I know that wiki is not always reliable but, in this case, it is correct. Why bother to raise the matter of wiki's editabillity? it doesn't make any difference to the error you made in the first place.

I don't think anyone has synthesised hexaphenyl ethane yet; there are plenty of similar examples where steric considerations make the molecule impossible. Still the question is a bit odd, I think that several hundred million different compounds have been synthesised. Which ones do you want big ones, smelly ones, left handed ones?

OK, thanks to the incompleteness theorem there are at least some things for which there is no answer. There are quite a lot of things for which, at least in principle, science can give the answer. Is there anything that can give an answer to (at least some) questions that fall outside the first 2 groups?

The point I was making was that whatever the cause; real or related to diagnostic criteria, there is a pressing neeed to do the research to check which it is. The idea the the NIH were looking into autism therefore there must be a link as expressed here "Also, why would NIH put so much effort towards this disorder if they did not feel it was truly on the rise?" is the idea I was trying to question. The other point being that the reported rise (whether it's different reporting or a higher true incidence) predated the use of the vaccine. That's a killer point against the "vaccine causes autism" argument. Whatever the cause may be, it could never have been a vaccine that hadn't been used yet.

Well, I think I know what a non Newtonian fluid is and I don't think you are right about it. http://en.wikipedia.org/wiki/Non-Newtonian_fluid There are plenty of thixotropic varnishes on the market, I don't know if they are clear before they dry. You might be able to find a dilatant mixture of a solid and liquid (that behaves like cornstarch and water) where the 2 components have the same refractive index. Even then you will have problems because the optical dispersions of the 2 materials are likely to differ. I might try powdered glass in glycerine if I were looking for such a mixture.

How does onion help? Is there any evidence that onion does help?

The true rate of autism (whatever that means) may be rising or it may be steady- it may even be falling. The reported rate is definitely rising. For the NIH and its equivalents round the world to ignore the rise in reported cases would be negligent; it falls to them to try to establish what the rise is due to. If it better diagnosis then we should rejoice; Autism isn't the easiest disease to treat but the first step is certainly to diagnose it. If there is a real rise in the rate of the disease then we need to know about it. If nothing else it would, in the long term, have an effect on healthcare spending. More importantly if it becomes more common then there is a greater need for research into the disease. We need to know what causes it and we need to know what we can do about it. The utter bollocks that was talked about measles and mercury does nothing to help those who are affected by the problem. It offers false hope to their families and it fills the pockets of those who, at the most charitable interpretation, have deluded themselves. Worse, it does this at the expense of real research into a real problem. Don't get me wrong, I know that sometimes you have to consider weird theories in order to find the true cause of things. H pylori and its role in ulcers is the classic example. The point is that the research should be judged in a scientific forum, not in court or (God help us) in the media. Distraught parents are not usually well placed to make judgements on such things. We really shouldn't let them get involved in that aspect of the work.

Why do people mix up homosexuallity with pedophillia? I understand that some peopel feel they are both "forbidden by my religion" and therefore equally wrong (though even that seems a strange opinion to me) but even then "equally wrong" doesn't mean "the same thing as". Most religious groups who condemn both of these groups also condemn infidelity in the same way. Yet the followers of those faiths don't generally mix up people who sleep with someone else's wife with pedopiles. Even the most devout (or deranged depending on your point of view) can tell that homosexuallity is not actually the same as eating shellfish even if they are both an abomination. So what is it? Why the blind spot? (BTW, just in case anyone's wondering- no I'm not a member of any of those groups but I'm hopelessly prejudiced against irrationallity)

When I was at school we were taught that one of the poperties of a gas was that it filled the container it was placed in. The He hardly knows about the CO2 so it will fill the container. So will the CO2. It would be a challenge to measure the difference in concentration with any sensible size of container. You have got the equation; why not use it and see what the answer is.

Nice gadget, what's the frequency response like?

Sepiraph, why do you say "At the very least it allows you to practice to be ambidextrous in writing"? Anyway, I gave up taking notes when I was a student. I realised that I was better off listening to the lecture and trying to understand it. In some cases the lecture was little more than the guy at the front writing out the textbook he had written, from memory, on the blackboard. Well, by simply buying the book I could avoid 2 sets of transcription errors and (more importantly) I could stay in bed rather than going to the lecture.

That's pretty nearly what I said except that 1) I don't think you will get the carbonate to decompose quantitatively to the oxide at any temperature low enough that you don't get significat loss of Na2O as the vapour. 2) I would have given the right formula for Na2O 3) you cannot do that titration with AgNO3 until you have acidified the mixture.

Oops! Sorry. You are quite right. What I should have said was that the reported rate of autism rose first.