h2g2 The Hitchhiker's Guide to the Galaxy: Earth Edition

A camel *can* pass through the eye of a needle if it passes through a blender first.

I wouldn't pass through the eye of the Needles except on a hovercraft during high tide on a very calm day. Do camels like traveling by hovercraft? (A87764539)

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Sodium chloride is contains sodium and chloride ions with stimulate pain receptors in tissue that would be protected from them by your skin normally.

Chlorine (which not the same as chloride!) is a flipping reactive, corrosive molecule - it will dissolve on mucous membrane such as your eye and cause lots of damage - hence it's antibacterial properties (it kills things) and the stinging sensation in your eyes.


Sorry did you want the right answers?

Your answer sounds good, Orcus.

Thank you.

I'm glad it sounds good - it doesn't read good (well ) upon a reread!

I think that chlorine and choride both can sting the eyes. I've had the same effect from sea water and from chlorinated pool water.

Utterly different reason though.

Chlorine is the element Cl and is a gas - that Cl-Cl bond is very weak and it's very oxidising and so is highly reactive generating hydrocholic acid when water is about which is up there with chlorine itself in its corrosivness to mucous membranes. It's super-nasty.

Chloride is it's far more stable form (it's gained an electron from the elementary form to be a negatively charged ion - it has eight outer electrons making it the preferred form in the presence of nearly all other chemicals) and hence is very unreactive and almost entirely benign as a chemical partner. Aside from it generating high osmotic pressures which might be painful to membranes like the eye because of high concentrations it's unlikely to do you any harm at all (it;s more likely to be sodium ions making you sting I suspect). High salt levels are of it will case very little harm to us - witness people deliberately going on holiday to the Dead Sea for it's (alleged) health benefits.

Oh one day I will learn to proofread before I post.

High salt levels (and remember there must be partner counter-ion - positively charged) will cause very little harm to us - witness people deliberately going on holiday to the Dead Sea for its (alleged) health benefits.

Note that I'm not talking about eating it - that's a different issue. (and then it's the sodium or potassium ions that are the actual issue).

By way of speculation, you have on the surface of all cells ion channels that preserve a balance of things like Na+, K+ and Cl- inside the cell - a high concentration of these on the outside is very undesirable. The cell membrane prevents them penetrating under most circumstances but there is always the chance of failure to vulnerable cells not protected by skin and as I said the high internal osmotic pressure this generates is bad for the cell.

So herein is my theory. You have receptors in your eye's cornea cells that will respond to the presence of high concentrations of either sodium or chloride (probably also K+) with a pain response to stimulate you or other sentient species to GTFO.




Chlorine is just deadly in many ways. Always a dose thing - we can just about tolerate the levels in swimming pools and it isn't *toxic* as such (depending on your definition), just massively corrosive in concentrations that are too high.

I appreciate your explanation.