Quick chemistry question, for chemistry-knowing peeps...

[Butcher]

And highly impractical/unsafe/stupid to carry in a survival kit/rucksack/pocket, I assume?

You could say that, depending on your viewpoint on carrying highly toxic chemicals that can only be contained in a limited number of metals (conveniently steel, copper and nickel are some of them). Oh and if you scratch the metal it will react, so make sure you don't damage the vessel.
Did I mention one of the things it will set light to is human flesh? Maybe forgot to mention that.
Also, not so great if you need to put it out as it can burn pretty much all known fire suppression substances.

It's on the previously mentioned Mr Lowe's list incidentally: http://blogs.sciencemag.org/pipeline..._you_this_time

Given this I can understand the concern. I think I'd personally be happy with the arrangement, but if it's easy enough to put them in separate containers then why not!

If there's a good reason for not carrying two tins - and I assume some people think there is, otherwise there'd be no point having this discussion - you could either pad the inside of the tin so the vials can't move around and pop open (although that might just be introducing additional flammable materials into the mix ) or put each vial in a small sealable baggy, so even if the top does pop open the contents won't be loose in the tin. Either choice would mitigate the vast majority of the risk you're concerned about.

I'd be tempted to solder a divider into the tin, though getting a seal on the top edge might be challenging.

[Ttaskmaster]

I think I'd personally be happy with the arrangement, but if it's easy enough to put them in separate containers then why not!

The filled vials come packed in the tins, which themselves are sealed in shrink-wrapped polythene.
You can buy vial-tins of magnesium, pot-perm and glycerine all from the same shop, but the shop themselves insists on sending them in separate jiffy bags, one for each substance.
If the shop itself ships them separately, that's usually a pretty good 'why not', to my way of thinking!

If there's a good reason for not carrying two tins - and I assume some people think there is, otherwise there'd be no point having this discussion

Space saving. Only reason. Not good enough, IMO.

you could either pad the inside of the tin so the vials can't move around and pop open

You mean like how they come packaged?
You'd think so, right....?

Thing is, they already carry two tins. The second one has vials of sugar and of glycerine, for the above-mentioned alternative methods of pot-perm flames, and yet they're sensible enough to keep those separate, so there's still a shred of hope... I just wanted something more substantial to my argument than "Tasky's Spidey Senses say so"...

You could say that, depending on your viewpoint on carrying highly toxic chemicals that can only be contained in a limited number of metals (conveniently steel, copper and nickel are some of them). Oh and if you scratch the metal it will react, so make sure you don't damage the vessel.
Did I mention one of the things it will set light to is human flesh? Maybe forgot to mention that.
Also, not so great if you need to put it out as it can burn pretty much all known fire suppression substances.

Oooooooooooohhhhhh.....!!
I think I might want some of that.... !!

I'd be tempted to solder a divider into the tin, though getting a seal on the top edge might be challenging.

The old SLR cleaning kits came in tins with three separated sections, but finding them for sensible money and without all the other gubbins included is seriously unlikely. I'm not paying £20-35 for a tin and some stuff I'm just going to throw away...

[ik9000]

I just wanted something more substantial to my argument than "Tasky's Spidey Senses say so"...

And yet, so often such an inkling is proven correct.

[Ttaskmaster]

And yet, so often such an inkling is proven correct.

You wouldn't think it from all the forum arguments and thread derailments I seem to get drawn into.....