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I know I shouldn't drink seawater (because of the salt it contains), but how can I desalinate it?

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Desalinate is the right word. It doesn't look like I can directly edit the question though. –  whatsisname Jan 25 '12 at 15:23

2 Answers 2

up vote 12 down vote accepted

You need to distill it - I'm assuming that freezing is not an option (unless you're camping in the extreme latitudes). This is easiest, as the ice on top is almost pure water.

Where you don't have a freezer available - boiling the water, capturing the steam and condensing it back to water will provide pure water.

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This method can be achieved using a plastic tarp or other impermeable membrane (raincoat). Boil water below, with the tented tarp above funneled into a container. –  Dangeranger Jan 25 '12 at 14:20
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If no heat source is available and you have a clear plastic tarp, use the solar energy of the sun to evaporate the salt water and capture the condensation. Make sure to angle the tarp and create a wrinkle for the liquid to drain into a container. –  Dangeranger Jan 25 '12 at 14:31
    
Distillation doesn't work 100%, the steam also contains some salt... when I was young I grown crystals and once I got for 1 week away. There was a book near the saturated salt solution where the crystals have grown. When I returned from vacation, it was completely covered with salty coating with crystals. So it doesn't work 100%. –  Tomas Feb 18 '12 at 11:18
    
it might not be 100% but it is better than nothing –  HorusKol Feb 21 '12 at 7:35

Outdoors you can dig a hole and build SOLAR STILL. It is quick and dirty but works very well and it is time tested.

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Or you can put big plastic bag over brach with a lot of leaves on it and put rock on the bottom to capture the water. Make sure you don't do it on foliage that is toxic to people.

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If you have the bucks you could get a portable Reverse osmosis filter.

Electrolysis turns the salt water into oxygen and hydrogen then recombine them and the result is pure water.

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+1 for the solar still: but how do you 'recombine' hydrogen and oxygen? other than combusting the hydrogen? –  HorusKol Jan 25 '12 at 22:00
    
@HorusKol: You burn them, and make a sizable explosion. Hydrogen is dangerous, and the danger arises from particular concentrations, which make it detonate, instead of burning. Also careful with the electrolyzed water. That most likely contains a mixture of bleach and lye. –  Stefano Borini Jan 26 '12 at 0:55
    
My recommendation for solar stills is to look for an appropriate dip rather than dig a hole since you'll sweat buckets digging, which rather defeats the object. The latter does not help with sea water. –  stevemarvell Aug 5 at 0:33

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