# John Cuthber

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1. ## Balanced equation

I don't think there's enough information to answer the question. As it happens the formula of hydrogen selenide is H2Se This decompses to give H2 and Se. The Se then reacts with the tin I think it will give SnSe- it might be SnSe2 but it doesn't matter because it takes up vrey little space whichever compound is formed. H2Se --> H2 + Se The H2Se and H2 have the same volume because there are the same number of moles of each. However, imagine that you chose H2Se2, the selenium equivalent of hydrogen peroxide. It too will decompose to give H2 and Se (which will be removed by the tin)
2. ## A plane on conveyer belt will it take off?

A couple of thoughts. 1 A plane flying in the right direction (heading into the sunrise I think) on the equator is, in effect, on a conveyor belt travelling at about 1000MPH (this conveyor is normally called the earth). This wouldn't make any real difference to its abillity to take off because the air is being dragged along by the earth. Any conveyor that could run under a plane that was trying to take off would drag an enormous amount of air with it. This would create at least some lift. Once the plane starts to rise the friction is reduced. If you raise the belt speed in order to try to c
3. ## Smoke which can be poured

In terms of the LD50 and such the bromides are roughly as toxic as the chlorides but, since bromides are used as drugs acting on the central nervous system, I would sugest steering clear of them.
4. ## Smoke which can be poured

Since all bromides are toxic I really wouldn't recommend tasting them or inhaling the smoke.
5. ## Silent Van de Graaff?

The problem is that, unlike a V de G, it doesn't help you at all. You might as well use a bit of wire connected to the power supply. With a V de G you spray charge onto a belt and the motor drags that charge towards the top sphere- in doing so it has to overcome the electrostatic repulsion between the charges on the belt and that of the top sphere. This means that work is done on the charges and their potential is raised. The current is the same as that sprayed onto the belt by the HT power suuply, but the output voltage is much higher. With an electron beam this doesn't happen so the output
6. ## Petroleum Ether

That mixture of hydrocarbons is fairly good at extracting things from water so, unless you happen to have something very water soluble in it as an impurity, washing with water won't remove the impurity. If on the other hand the stuff is very water soluble then it's unlikely to disolve in the naptha in the first place. Having said that, it looks like you have found a source of pet ether which was the original problem.
7. ## Petroleum Ether

Can anyone else see why this "Shellite from the hardware store is generally an ok substitute for backyard extractions" is exactly why this "if you dont trust it's purity wash it with distilled water before use (ie add water, shake, let separate into layers - the shellite floats ... discard water layer from the bottom)" may not work very well.
8. ## Phytoestrogen = estrogen = gay

Yes, if you are eating "the pill". Otherwise the body's feedback mechanisms make sure that the effects are tiny, certainly less than the natural variation in hormone levels from one person to the next. Anyway, the idea that eostrogens make you gay is utter balderdash. Don't forget that all of us, while in utero, were exposed to female hormone levels nearly as high as our pregnant mothers. If that exposure led to homosexuallity then there simply wouldn't be any straight men.
9. ## Copper contamination

Last time I was doing this I precipitated the silver with sodium acetate and washed off the copper acetate (you lose Ag this way but you can always recover it as chloride). If you want to get the silver then you can heat the acetate carefully so it decomposes. Since the acetate is slightly soluble you should be able to convert it to Ag2O with excess NaOH, wash it then redissolve it in HNO3.
10. ## Pyruvate reduce body fat?

Don't forget that if it looks too good to be true it probably is. IIRC pyruvate is naturally present in the body, created and used up rapidly so adding a little wouldn't have much effect.
11. ## Imaginary numbers

Fractals, like those generated using imaginary numbers, are used for data compression which is reasonably important in this www world. I don't know if the particular fractals they use are calculated using imaginary numbers. "I just fail to see how this makes the equation any more solvable. You still can't have the square root of a negative and just because you put an i down doesn't change this." That's a fair point but I think there are 2 answers. Firstly the mathematicians are happy because now they can write down an answer. If they had to keep on making up "strange" numbers in order
12. ## Brain teaser

Because we have to shed the waste heat that metabolism generates. We can do that by sweating (the heat is used to evaporate the water) but it's easier to do it if we can lose heat simply by conduction to the outside air. Normally the skin is a fair bit cooler than 37C so the excess heat is conducted (as well as carried by the blood) to the skin. When the air temperature is as warm as 37C we have more difficulty losing the waste heat we generate.
13. ## calculator fun

Or, if you prefer a geometric equivalent, the 2 halves of the expression on the right are 2 triangles, put together with a line of n "stars" they form a square. * *** ** ** *** * **** Can someone who understood that and who has a better graphics package than me draw that please?
14. ## Barnoulli's principle

"the basics behind why planes fly." The classic explanation of how planes fly must logically be wrong. Stunt planes can be flown indefinitely upside down. As for "PLEASE COMMENT" how about, this post is in the wrong place and please don't WRITE IN CAPITALS. As insane alien said a pipe with a fast flowing liquid stream will tend to colapse but the effect is usually small.
15. ## Silent Van de Graaff?

The idea of using beta emitters directly as a source of electricity does work. The currents involved are tiny but the voltage can be huge. As for pointing an electron beam at an isolated metal sphere it sort of works but, once the sphere has the same voltage as the accelerator potential of the electron gun the electrons are repelled but the negative charge and the no more current flows onto the sphere. You would do just as well to connect a wire from the high voltage source to the sphere directly.
16. ## rate of a chemical reaction

The reactants get turned into products so, at any given time the rate of change of ammount of reactant with time is negative. Imagine we start with a gram of reactant and that after 5 minutes there is half a gram left. The change in amount of reactant is minus half a gram and the change in time is 5 minutes so the rate of change is -0.5/5 ie -0.1g/min Since we prefer our constants to be positive we chose to use the expression dx/dt=-k[A] (with a minus sign in it.) It's a matter of convention; we could use rate negative constants but they would look odd.
17. ## Need help with Alka-selzer

It's not exactly a well kept secret what goes into the tablets. Ingredients Active Ingredients: Each Tablet Contains: Aspirin (325 mg), Citric Acid (1000 mg), Heat Treated Sodium Bicarbonate (1916 mg). Alka-Selzer in Water Contains Principally the Antacid Sodium Citrate and the Analgesic Sodium Acetylsalicylate. Inactive Ingredients: None. BTW, the equation in the first post doesn't reflect what is going on here; in fact that reaction goes the other way.
18. ## amides

Sulphonic acids give sulphonamides, phosphoric acids give phosphoramides carbamides are another variation on the theme too.
19. ## Good and bad chemical smells, list yours

"in fact I would go so far as to say that NON of the metal elements have a smell exactly (nor their oxides), " YT2095, you might wish to look up the origin of the name "osmium" though I grant that it's unusual.
20. ## Acids from salts

Nitric acid reacts with HCl which pretty much rules it out. Often the scheme is to add an acid to a salt then distill out the acid. There needs to be a reason why the reaction goes in the right direction ie the way you want. With sulphuric acid (boils about 300C) you can remove the acid you want eg HCl, acetic, nitric by distilling it. If you were to mix HCl with sodium acetate you would certainly get acetic acid produced. However if you were to try to distill out the acetic acid at least some of the (volatile) HCl would also come over. With H2SO4 that's not going to happen. H2SO4 is also ch
21. ## How big is big?

There are about a trillion hits on Google for "amino acid analysis" HPLC. Most of them involve reacting the amino acids with something to make them easier to detect and less polar. This one seems pretty typical. http://www.canr.msu.edu/comparativenutrition/Amino%20Acid%20analysis%20of%20Hydrolysates.doc I can't say I've tried it but it looks like a good place to start. Of course, that's OK for a UV or fluorescence detector. LC/MS can be a bit fussy. You will need a volatile buffer rather than sodium acetate and you might need some clean-up stage.
22. ## Emerald juice

I know you are not going to leach a lot of Be out of emeralds but it's nasty stuff so be careful. BTW, congratulations on finding the commonest of the transition elements.
23. ## Copper or Gold?

"How can I tell if a particular bored is made of Gold or something less valuable like copper?" Gold is golden in colour whereas copper is copper coloured. The gold plating is very thin If you are setting up a "collection of the elements" then old circuit boards are one of the few places you will get gold for free.
24. ## Benzene - complete ring substitution.

Part of the problm for making a hexanitrobenzene is that each nitro group you add removes electrons from the ring and makes it more difficult for the next substitution to happen. It's possible to add methyl groups to a benzene ring using chloromethane (or, more practically iodomethane) and a lewis acid catalyst like AlCl3. If you do this you tend to get more than one methyl on each ring because the methyl benzene is more reactive than benzene itself and, similarly the dimethyl benzenes are more reactive still. Getting all 6 to react isn't as easy as it looks because of steric effects.
25. ## (UpDated)Clock hands radium paint...

Most of the alphas just crash into the Bi and are slowed down, pick up a couple of electrons and are converted to He gas. A tiny percentage are caught by the Bi nuclei and form 210At. That At will, in time decay largely by electron capture (and give off a gamma ray) Partly by alpha emmission. Of course, that all depends on having 206Bi to start with and, since it has a rather short half life (about 15 days), you almost certainly don't have any. I doubt that the relatively stable 209Bi traps alphas to any great extent - not least because it's a (very weak) alpha emmiter. Overall, I'm not s
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