Caspian Sea drinking

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Caspian Sea drinking

Postby Braininvat on March 8th, 2014, 11:34 am 

Have strayed from my usual physics/philos. haunts in hopes of settling a recent chat regarding the Caspian Sea. It has a salinity of approximately 1.2%, about a third the salinity of most seawater. Does this mean that, as with most seawater, that you cannot achieve any hydration by drinking it? (presuming a lifeboat situation, with water stores gone, and no rain coming) Or is that low enough that one might get a bit of relief from thirst?
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Re: Caspian Sea drinking

Postby Natural ChemE on March 8th, 2014, 2:28 pm 

Braininvat,

A quick Google search seems to suggest that human blood's about 0.9% salt, so the water'd have a higher salinity. Probably not hydrating.

This said, perhaps it's possible that a severely dehydrated person has a higher salinity? It seems plausible that a severely dehydrated person might be become somewhat less dehydrated by drinking it.
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Re: Caspian Sea drinking

Postby BioWizard on March 9th, 2014, 8:47 am 

I think you guys might be oversimplifying the problem here. The reason I say this is because your bodies don't absorb nutrients by passive osmosis _down_ a concentration gradient. If they did, you would have had to pay enormous attention to what you drink so that you don't pee out all our nutrients and electrolytes. Rather, your guts have active transport mechanisms that can mop up things like simple sugars, amino acids, and electrolytes _up_ a concentration gradient. This ensures that you absorb nutrients even when their concentration in the gut is lower than their concentration in your blood. That said, the reason salt water isn't very hydrating isn't because it is more saline than your blood, but because all the excess salt that you absorb from it will have to be excreted in the form of sweat or urine. This will drain water from your system, and depending on the amount of salt you absorb, it might require a larger volume of water to excrete it than what you consumed with it, putting you at a net zero gain or even a loss.
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Re: Caspian Sea drinking

Postby Braininvat on March 9th, 2014, 2:28 pm 

I think you guys might be oversimplifying the problem here....
In my case, that is a certainty.

Thanks for at least giving me a handle on the problem. So it's possible that Caspian seawater, being only about 30% more saline than blood (when normally hydrated), might stave off severe dehydration. Whereas ocean water wouldn't. Not like I'm going to put this to a test...
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Re: Caspian Sea drinking

Postby BioWizard on March 9th, 2014, 3:15 pm 

I can't give you an educated guess without doing some math. Compare it to gatorade I guess, that might give you some reference. Gatorade was optimized experimentally. Though it also has a lot of sugar (which dramatically increases water absorption), so it's hard to compare it to just saline solution.
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Re: Caspian Sea drinking

Postby dingbat on March 8th, 2016, 2:25 am 

In 2016, Google still doesn't give a ready answer to this question, so I'm registering and posting in this old thread to file away a partial answer for the interweb.
I study the history of science, especially classical Greek and Roman natural philosophy. Pliny the Elder, in his Natural History (written in the mid-1st century AD), remarked on the potability of the Caspian Sea:

Haustum ipsius maris dulcem esse et Alexander Magnus prodidit et M. Varro talem perlatum Pompeio iuxta res gerenti Mithridatico bello, magnitudine haut dubie influentium amnium victo sale. (Naturalis Historia VI.19)

I translate: "Alexander the Great reported that water taken from this very sea was fresh, and Marcus Varro reported that he brought fresh water [from it] to Pompey during the Mithridatic war; no doubt the explanation is the size of the rivers that flow into it and defeat the salt."

Alexander would have tasted the Caspian in the late 4th century BC, Varro in the mid-1st century BC. It's possible that the Caspian's inflows and/or salinity have changed since then, but if not, then apparently its water is fine to drink. And maybe contains a secret ingredient which empowers an armed force to conquer the known world?
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Re: Caspian Sea drinking

Postby doogles on March 8th, 2016, 6:49 am 

When I saw this thread I recalled that some research had been conducted in the 1950s following reports of many shipwreck survivors dying of thirst during WWII.

I found the report on http://www.pangolin.co.nz/node/8 :-

In 1952, Dr Alain Bombard - doctor, scientist and voluntary castaway commenced a series of experiments using himself as a castaway in a 15-foot Zodiac inflatable. He had a companion for an initial trial run in the Mediterranean, but later completed a 65-day stint on his own in the Atlantic. “The spectacle of a pile of corpses of drowned fisherman in Bologne (France), prompted him to discover that thousands died annually at sea. His further researches showed that many could have lived: despair and terror were the real killers, not exposure, starvation or dehydration.”

“As a doctor he reasoned that salt is part of the human diet (10gms, 1/2oz daily) and that it would be safe to drink small amounts of sea water in which the salt content did not exceed the normal – and necessary – daily intake. Plankton would provide him with vitamin C and thus prevent scurvy. Water was the castaway’s biggest problem, but 50-80% of the body weight of pelagic fish is water or liquids. In his inflatable he carried a squeezer modified to extract water from fish.”

“They had a radio with a hand-cranked battery charger, which – as Bombard expected - was to prove useless. They also had fishing lines and a fine net designed to catch plankton; and Jack had his sextant, his almanac and his tables, but no other aids to navigation and there was no support ship, nor back-up of any kind.”

I read somewhere else that his way of drinking seawater was to take a spoonful into the mouth every 20 minutes, to allow it to mix well with saliva for as long as possible before swallowing. His rationale seemed to be that he could drink an amount of seawater containing 10g of sodium chloride daily. This is much higher than our currently recommended total daily intake of 4g. And it does not allow for the amount he would imbibe from raw fish and plankton. If seawater contains 3.5% dalt, he would only be able to drink 286 mL daily to recive 10g. During a waking period of 16 hr, this would be 6 mL evry 20 minutes - hence his approx. teaspoonful every 20 minutes. That low amount of fluid would seem to me to be pushing the boundaries, but on the other hand, he could not have been taking in much raw fish or plankton to lose the amounts of weight described in the Atlantic journey below.

During his solo trip on the Atlantic he was alone till day 53 when he boarded a passing ship briefly and then continued to day 65.

“He had lost 55lbs in weight. He was seriously anaemic and suffered various minor ailments, but not from dehydration nor from scurvy.”

He lived from 1924 till 2005, so the experience does not appear to have caused any long-term harm. I have seen some references suggesting that he was not totally honest with his reporting, but at the same time these criticisms consisted of innuendo rather than substance. There was a report that another adventurer, Dr Hannes Linderman made two solo crossings of the Atlantic in the 1950s. He is said to have experimented with survival by drinking seawater, but I have been unable to find any solid references to these tests. Linderman took plenty of supplies and was in good shape at the finish of his advebtures.

As yet, no one appears to have been game enough to repeat the experiment of Bombard and there do not appear to be any reports of castaways surviving dehydration by using seawater wholly or partly as a fluid supply.

If in fact he did survive, even partly, on Atlantic salt water at 3.5%, the Caspian Sea water at 1.6% would be far less of a problem.
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Re: Caspian Sea drinking

Postby Eclogite on March 8th, 2016, 7:25 am 

I suspect the main problem with drinking Caspian water may not be the salt, but the pollution. (That is merely a suspicion based on reasonable consideration of the disregard for environmental issues of those countries and former states of the USSR that discharge into it.
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