John Cuthber

The post Klaynos refers to gives the limit of resolution for the eye, but that's not the smallest thing you could see. A brightly lit speck of dust smaller than that limit would still be visible against a dark background.

To say this "Small children with attention disorders " implies that you have already lost the battle.

If they have that problem then it must have been in their makeup before. In that case to punish them is unfair as they can't help something they are born with.

Jdurg, I don't think it falls to us to prove your error. You are the one making the claim that something unusual happens so it is your job to prove it.

However, the phase diagram give in IA's post could only have been produced by someone who did essentially the experiment you are talking about (at lots of different pressures). I accept it's not on video, but it is evidence.

I've made plenty of errors. I just don't usually resort to ad hom attacks on those who point them out.

Cordial is something I can leave to others to judge.

This website is about science- ie knowledge. In order to be of any use it needs to be accurate, therefore I consider my post correcting your error to be helpful to the board in general. As you say, "The point of a public forum is to help people", we can't do that by posting stuff that's incorrect.

Perhaps you might like to explain why you chose to post something which was both off-topic and incorrect, before criticising what I posted.

"I've never seen it on a wide open surface before "

From the point of view of an iodine molecule, a test tube is a wide open surface.

"Put it in a test tube and the vapor will sit on top and create a higher pressure at the surface of the I2 making the liquification much easier because there is a greater localized pressure"

The test tube has roughly 70 miles of air above it exerting about 760 mmHg pressure.

From the data above, the vapour (in a sealed container) would only add about 130mm Hg to that. Since the tube is open the additional pressure is only the weight of the few inches of I2 vapour in the tube which is obviously tiny compared to the 70 miles of air.

It's interesting to see that the case of I2 is closed. In reallity, you can melt it in a test tube.It's nothing special. Since it's pretty volatile, you get a lot of vapour too, but if you pre heat the tube to a temperature between the melting and boiling points ( not too difficult) you readily get the liquid phase. I'm not wasting my time videoing this just because it will "stun" Jdurg.

For a start you need to find out what standard means.

There's nothing special about molten I2. It melts at 114C and boils at 184C. Between those temperatures, at normal pressures, it's a liquid.

What do you mean by "The standard pressure of gaseous I2 will cause the iodine to form a liquid."

The lead chamber process produces SO3 http://en.wikipedia.org/wiki/Lead_chamber_process

Oxidation of sulphurous to sulphuric acid ought to take placre in air, I'm not sure how fast it is.

I'd also not like to have to balance the equation of the sulphur/ KNO3 reaction, partly because there's not much point. The reaction will not go perfectly and there will be by products.

"Maybe you could get an electron gun with a phosphor screen. Although electrons at these energies are not ionizing,"

Oh yes they are. If it's got enough energy to produce visible light it can ionise at least some things. The electrons in CRTs are rypically at 10KV; ionisation potentials are typically a few volts.

It may be due to the fact the some rechargeable batteries go flat relatively quickly, even if they are not doing much. That's not good for a timer.

"Please tell us where you found positive oxygen ions?"

Here

http://en.wikipedia.org/wiki/Dioxygenyl

It's a bit more complicated than that.

If you took 36.5 ml of conc HCl it would weigh about 43 grams because the density is about 1.18 g/ml. Of that about 35% is actually HCl, the rest is water, so you would have 15g of HCl. That's only about 0.41 moles, so if you made it up to 1 litre you would have about 0.4M HCl.

From that definition (an oxidant used in rockets), oxygen is pretty nasty stuff.

"i happen to know that if all bacteria were removed umans would not live more that 2 hours."

OK, for the last couple of hours before I was born I had no gut bacteria but was otherwise practically identical to the first couple afterwards; I lived. How come?

I'd quite like to know where you get the ninth power of anything in a physical system.

not sure if they are all able to be gotten w/o a license, i'll have to look. skimming it looks like what i want is precipitated when i add something that meets the test requirements to the solution though.

 

The materials are available and you are right- Cu2O is precipitated by adding glucose and heating the mixture.

Capt. Panic is right about heating things in sealed containers.

However what I had in mind was something based on this

http://en.wikipedia.org/wiki/Fehling's_solution

Is your chemistry up to working out the rest of it, or do you want a hand?

"Easy" isn't well defined here but if you can get hold of copper sulphate, cream of tartar (or citric acid), bicarbonate of soda (caustic soda will make things easier), and vitamin C (or glucose) it's possible. Do those count as household chemicals?

"And as far as "i" is concerned, far from being "impossible" or even "improbable", it certainly does exist and is used regularly in physics or even engineering."

No its not, it's used in mathematically modeling physics and engineering.

Once you convert the model back to reality "i" goes away.

If you calculate the displacement of a bridge in a strong wind is something like (5+3i)mm you have got the answer wrong.

The simple answer is that, for CO2, the melting and boiling points in that table are not measured at the same pressure so it's not comparing like with like.

Most materials do what CO2 does, it's just that we happen to chose atmospheric pressure as our standard.

If we lived on a planet with a very low atmospheric pressure (below about 0.006 Atm) we would think of liquid water as some weird state.

(I'm ignoring the difficulty of life in the absence of liquid water).

Solids have a finite vapour pressure at any given temperature- if that pressure excedes the external pressure then the stuff will sublime. At a lower external pressure the temperature required to get the stuff to sublime will be lower.

For a low enough external pressure that will happen at a lower temperature than the melting point.

There's nothing magic about CO2 except that it happens to behave this way near normal temperatures and pressures and is common enough that we hear about it.

It will dissolve better in hot solvent (but be aware of the fire risk).

It may be possible to change the base and thereby produce a more soluble derivative but that would need to be sorted out experimentally.

I seem to remember that chlorinated phthalocyanines are greener than unsubstituted ones. However producing these isn't going to be trivial.

Might it not be easier to find a different dye/pigment?

Water vapour does have a higher heat capacity than air; but that's not the whole story. It also has a higher conductivity.

Imersed in wet air (a better conductor) your surface attains a temperature nearer that of its surroundings than it would surrounded by dry air (a poorer conductor). If, as in the OP those surroundigs are colder than you, you will feel colder in wet air.

The original question was about 0.0recurring1. That has a meaning of sorts. It's the difference between 0.9recurring and 1

It's the limit (though not, I think, in the strict mathematical sense) of

1-.9=0.1

1-.99=0.01

1-.999=0.001

and so on to

1-.9recurring= "0.0recurring with a 1 tagged on the end".

From that point of view it's a perfectly reasonable concept. It happens to be another way of writing zero.

Once you accept that you can label some of these weird (and very near useless)figments of imagination as having certain properties you can look at those properties.

For example, in the same way that 0.95 is between 0.9 and 1 you can see that

0.9Recurring5 is between 0.9recurring and 1

It's not physically meaningful, but (as has been pointed out) nor is i. That doesn't stop mathematicians playing with it.