The Science of Water

[Ray Britton]

ged said:

We could even, if we really wanted to, consider ways of absorbing water that don't involve drinking it.

Hmmm, do you fancy a bit of rectal infusion?

We could talk about it, but then it would upset all the posters who have gone to SO much trouble to tell us how to sterilise our water!

Of course if you really wanted to get obtuse on this, then we could get into ways to boil water at lower atmospheric pressures....But at sea level!!

Have any of you out there ever boiled water at less than 100 degrees C at sea level?.....I know its hardly practical, but is an interesting thing to see

 

[CaptainBeaky]

Of course if you really wanted to get obtuse on this, then we could get into ways to boil water at lower atmospheric pressures....But at sea level!!

Have any of you out there ever boiled water at less than 100 degrees C at sea level?.....I know its hardly practical, but is an interesting thing to see

Yes, I have, but in a lab, crystallising out some stuff which didn't like anything over 65C. Had to get it down to under 100mmHg to avoid decomposing the product when evaporating off the water...

Not really something you can do out in the woods (unless your rucksack is a lot bigger than mine )

 

[Ray Britton]

Hi Captain.

There is a slightly easier way (well, for that read: massively easier way).
Pop your very hot water into a wine bottle, and fit a wine vacuum sealer onto it. As you then pump out the air, the pressure will drop and the water will start to boil. Once it stops boiling, just pumped out some more air, and the water will boil again.
Thus you can have water that has never reached 100 degrees, but has been boiled enough to sterilize it.

Why would I need to get into a situation where I can only heat but not boil my water? I hear you ask?.
You could perhaps of found an old wine bottle, and an old fizzy drinks bottle.....You could heat the water in the fizzy drinks bottle on the embers of your fire until the water is nearly boiling (not forgetting to keep the fizzy bottle lid away from the ashes),, then decant it into the wine bottle.........As for finding the vacuum keeper, just make something else up

 

[CaptainBeaky]

Ray:
Unfortunately, it's temperature, not evaporation that does the sterilisation, which is why autoclaves operate at high pressure - to increase the temperature achievable in the chamber.
Reducing the pressure so that water boils at a lower temperature also reduces the sterilising effect.

 

[ged]

Getting back to science:

http://www.bbc.co.uk/news/technology-10858815

 

[Ray Britton]

Hi captain Beaky.
Yep, I knew that thanks lol, hence my comedy stance of the wine bottle thing, and the smiley at the end.
I was just throwing in an obtuse way to do something, which can be amusing to see (and done at sea level), rather than being a pedant. Having been loosely involved with water (and potable water) for twenty years, I have learned that to be over pedantic can lead to confusion lol.......Such as pointing out that it is not steam that comes from the top of a kettle...Or from a steam iron lol, or that central heating boilers don't boil, or that radiators mainly convect, not radiate. Another fun experiment is showing that water does not always find its own self level (which goes against what is taught at school), hence gravity hot water heating systems.

On the other hand, if I were in a cheeky mood, I would point out that evaporation is actually an excellent way to obtain pure potable water (but not strictly sterilized), and can be done at quite low temperatures too when used with a solar still, rather than the traditional type of still. The good side is whether you are using a still, boiling or an autoclave as you rightly point out, its all SCIENCE based, and all good fun.

I have to admit, your evaporation comment did make me chuckle (as it does take a while to sterilize water at 65 degrees lol)

Uh oh, thread drift again lol Smacks wrist, and sits in naughty corner.

 

[CaptainBeaky]

Hi Ray
Dunno - being over-pedantic and confusing can be quite amusing at times The difference between evaporation and boiling is always a good one with which to tease the unwary

And definitely don't start on gravity-fed HWS - the number of hours spent grinding my teeth over airlocked hot water systems in the last 20-something years... Pressurised every time - please...

 

[Ray Britton]

Captain Beaky.

How right you are over air locks!
It gets worse when you try to explain to the customer that their water is somewhere up in the pipework, but isn't coming down to play.........Which is always followed by them stating 'but water always goes to the lowest level'

Maybe in school experiments, but not in the real world lol

 

[Steve M]

So, I've mostly been reading about bacterial spores. Any thoughts on managing those bad boys in a survival context?

 

[ashes1627]

Good post, thanks for this! Great work! :You_Rock_

 

[HarrogateTobias]

what is the name of the "high tech" 58 water bottle pump? very interested as i might be afghan in the next few years?

 

[British Red]

Its a PreMac MWP

http://www.pre-mac.com/MIL_P1.HTM

 

[raspberryjam]

That was very well written, well done

to add to the boiling/temp/alt debate...

"Heating water to a high enough temperature for a long enough time will kill all dangerous organisms. Advice from reputable sources varies but consensus seems to suggest that raising water to 100C will have killed all bacteria and viruses. Cysts are a little tougher and advice is to maintain 100 degrees C for one minute to be safe." (sorry haven't mastered quoting yet)...

This is a common misconception and incorrect. I'm an environmental scientist, my field is water, and have just spent the last year writing about the health risks posed to humans by cyanobacteria aka blue-green algae. Cyanobacterial toxins (which can potentially kill) are not removed through boiling or filtration. I can't comment on chemical sterilization methods but the best way to reduce exposure to cyanobacterial toxins is to take your water from a fast running, very cold, mountain stream.

Another example of how boiling is inadequate would be the bacteria found in boiling geysers.

 

[British Red]

Blue green algae are interesting. I believe the quote is correct in that boiling will in fact kill cyanobacteria, it will not however remove the chemical toxin that the bacteria has already created...in this way cyanobacterial toxins need to be treated as other chemical contaminents.

Would you agree with that (i.e. that cyanobacterial toxin is not alive)?

Red

 

[raspberryjam]

No boiling doesn't eliminate all strains of cyanobacteria particularly the micyrocystins. And as boiling results in cell abrupture some toxins are actually increased.

 

[British Red]

Thats fascinating - thanks for the info. I wish it was more widely available (e.g. in the WHO advice etc.)

 

[raspberryjam]

Sorry that should be microcystis not microcystins.
Yep I know but the data given in the WHO guidelines is from 1998, and its a badly researched area as most cases of illness resulting from cyanobacteria are inconclusive due to people being unable to directly attribute their symptoms with them being so wide ranging. My own study showed that people were unable to identify any potential hazard posed from cyanobacteria even when the amount present was in the highest value given by WHO in their guidelines for drinking water quality.

 

[raspberryjam]

Apologies I have misread...

You're right in that cyanobacteria can be destroyed by boiling however this can increase the toxins released particularly from microcystis...but to say that boiling at 100 degrees and in the case for cysts at least a minute is misleading, but you have pointed out 'for long enough time'...

lolol very sorry it's been a long long day :theyareon

 

[Elines]

There is a device for testing whether or not water has been 'boiled' enough. You can find it at

http://www.solarcookers.org/catalog....html?osCsid=d5a99bf3f5ae71f339a905e68df85e2b

This is saying that you only need to pasteurise water to 65 degrees C for a short period for it to kill microbes, including E. coli, Rotaviruses, Giardia and the Hepatitis A virus. This might be really helpful when you are at altitude and cannot boil water at 100 degrees C. The device itself is very small and lightweight. The glass tube is about 1 inch long (I think).

 

[ged]

There is a device for testing whether or not water has been 'boiled' enough. ...

Nice find Chris, and not as expensive as sometimes things in this, er, neck of the woods can be. Any idea what it weighs?

Something like that could be handy if, say, you're very short of fuel. If not, I think I'd still opt for ten minutes at a rolling boil, just to be on the safe side.