I suspect that the psychological effect of planting the idea that, a small amount of dilution is acceptable, would be counterproductive in real life situations. You don’t want a half deranged survivor in a life raft thinking, “Hmmm, I remember that it’s OK to drink a little bit of seawater…”, much better to ingrain the idea that, “seawater kills, do not drink any”.
Some dilution is likely to occur in the act of catching rainwater, that would probably negate any advantage possible in purposfully adding seawater to fresh supplies.
Ding!
I believe we have a winner.
So, since each liter of seawater contains 35 grams of salt, we pour out 430 cc of it and the remaining 570 cc contain 20 grams of salt. We then add 430 cc of fresh water and we have a 2% solution, by weight, which is OK. Do we really believe that?
And if we are speaking of molar concentration the molecular weight of salt is 58.43 so 35 grams is .599 mole. The molecular weight of water is 18 so 1000 grams is 55.56 mole. We have a molar concentration of 1.1% so we can add maybe 30 grams of salt to our sea water and still be safe.
Nathanile Philbrick, in *The Heart of the Sea * if I recall correctly, states that despite the widely held belief to the contrary, you can safely ingest 1 part salt water mixed with 3 parts fresh water. While not a doctor, Philbrick does excellent research a knows his nautical history, so I have no reason to doubt what he said.
Hmmm, now, if you diluted the freshwater with urine (rather than drinking the urine straight), would that substantially alter its taste?
Also, if it would give your freshwater that patented peony taste, would a little bit of sea water help mask the urine flavor?
Also, I know that urine is supposed to be at worst not very harmful and perhaps harmless from a bacterial perspective, but what if you were stranded on a lifeboat with a communal source of water, would you want everyone urinating in the same place to delay the day when you’ll have to drink straight urine? I can’t imagine the calculations you’d have to go through as to whether you’d be more likely to be rescued before having to resort to that, or what your chances of infection would be given the number of contributors to your liquid.
I seem to recall a “Survivorman” episode where Les Stroud noted one case where some disaster (shipwreck?) survivors were able to keep alive on somewhat brackish (though not pure salt) water, that would normally be unsuitable for drinking…via enemas. The Colon being able to absorb water (normally from…er, feces)…
I think I’ll leave this to someone else to test out, or check the status of research on. :eek:
I recently read something (though not this particular book) that said about the same thing. Blake’s post estimates a similar mixture.
(Well, 3:1 is a lot different than 1:1, but not when compared to 100:1.)
Hmmm. Now all I have to do is find my source. And then have the gonads to contradict QtM. 
That doesn’t require gonads. Just facts.
If my memory serves me correctly, in this book Philbrick also asserts that drinking urine, while not overly harmful, is actually less helpful than drinking the 3:1 diluted seawater mixture.
So perhaps the smartest thing would be for the survivors to urinate up each other’s rectums. And whilst doing so, I suppose the most appropriate utterance would be “Yarrrrrr!”
Now if I could just figure out how to write a mystery for this phenomenon…