Difference between revisions of "Chemistry of common things"

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m (On water poisoning)
m (Salty water)
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The amount of salt in seawater (3.5%) isn't just much more salt than you need, it's many multiples higher than the concentration of salt in water in you.
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The amount of salt in seawater (3.5%) isn't just more than you need, it's ''multiples'' higher than the concentration of salt in water in you.
The precise concentration varies, but the average is somewhere around 0.15% in most of your body, and up to ''maybe'' 0.9% in your blood{{verify}} because it helps regulate.
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The precise concentration varies around your body, but the average is around 0.15% in most of it.
 
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Blood concentration is higher, maybe 0.9%{{verify}}, because it helps regulate your body.
...so anything stronger leads to [https://en.wikipedia.org/wiki/Osmosis osmosis]: drinking water that salty it pulls water out of our cells, eventually dehydrating our cells throughout your body.  It starts in the gut, because that's where most water you drink is absorbed.
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...so water saltier than that leads to [https://en.wikipedia.org/wiki/Osmosis osmosis], the net result of which is that water gets pulled out of our cells, eventually dehydrating the cells throughout your body. 
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Which starts in the gut, because that's where most water you drink is absorbed.
  
  
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and more importantly, the kidneys use water to dump what it collects.
 
and more importantly, the kidneys use water to dump what it collects.
  
It turns out that there is a maximum concentration of collected salt your kidneys can put into water you pee out.
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It turns out that there is a maximum concentration of collected salt your kidneys can put into water you pee out,
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above which salty water represents a net loss of water.
  
Which means drinking water saltier than that, and your body is going to have to ''add'' water to get rid of said salt.
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The tipping point for this is well under the concentration in seawater - ''roughly'' half.  
  
  
The tipping point for this is well under the concentration in seawater - roughly half.
 
  
Put another way, your kidneys can only make urine that is less salty than seawater, so you have to pee more water than you just drank.
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Seawater doesn't hydrate you even in the short term.  
  
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Maybe in a very technical sense that it's water inside you,
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but it's not available yet and there is no way for the salt to not come along,
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so it dehydrates you faster than the water involved can hydrate you.
  
The water you drank does hydrates you a little only in the most technical sense that it is also inside you,
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While not ''immediately'' harmful, it also at no point in time helps you.
''but'' the salt is going to always come along, and effectively ''dehydrates you much more'', and no slower than that this water can hydrate you.
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It's not even a useful stopgap in any way.
  
So while the act of drinking seawater isn't ''immediately'' harmful,
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It really ''only'' makes things worse, because many processes in your body are going to have a tougher time.  
the net effect is dehydration at any time.
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This basically means that at no point in time does drinking seawater hydrate you - it's not even a useful stopgap in any way.
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It really ''only'' makes things worse, because many processes in your brain are going to have a tougher time.  
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Not least important is the brain - your judgment will not get any better.
 
Not least important is the brain - your judgment will not get any better.
 
  
  
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Saline solution is often around 0.9%, which is roughly isotonic with our blood, but not our body in general (0.15%).
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Medical saline solution is often around 0.9%, which is roughly isotonic with our blood, but not our body in general (0.15%).
  
  
The goal of a saline IV is basically ''mobile'' water, so that it can get around and be used where necessary, quickly. (this is still rather oversimplified, though)
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Our blood is our body's main means of regulating salt (and many other things).
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The goal of a saline IV is basically ''mobile'' water, so your body can move it to where it is needed, quickly. (note: this is rather oversimplified)
  
Much sooner than drinking a bunch of water would, as regular water uptake mostly happens in your gut, and can take a while to get there and all get absorbed - it can take many hours to rebalance after serious dehydration.  
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Saline IV puts water in your blood much sooner than drinking a bunch of water would - getting water via your gut means it can take hours to rebalance after serious dehydration.
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It will work, and drinking water is ''also'' still a good idea, but saline IV can be ''necessary'' when dealing with serious dehydration.
  
Drinking water is ''also'' still a good idea, but saline IV can be ''necessary'' when dealing with serious dehydration.
 
  
 
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Saline solution is 0.9% because that's our blood levels. Any other concentration would mean your body having to do more work.
But too high an IV concentration, and your body wants to draw water into the bloodstream (dehydrating cells directly around), too low and it pushes water out (which isn't useful, but more importantly, could kill red blood cells).  
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Too high an IV concentration, and your body draws water into the bloodstream (dehydrating cells directly around).
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Too low and it pushes water out (which isn't useful, but more importantly, could kill red blood cells).  
 
Lower-than-isotonic IVs ''are'' used, but with some practical footnotes.
 
Lower-than-isotonic IVs ''are'' used, but with some practical footnotes.
  
 
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At the same time that we are keeping our bloodstream happy, we ''are'' plain adding salt to the body,
While this salt is important to make our bloodstream happy, we ''are'' plain adding salt to the body, that you may not need, and that it needs some water to expel.
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and if it's more than you need, it will need some water to expel.
  
 
But the rate, though steady, is low enough that our body can deal with it.
 
But the rate, though steady, is low enough that our body can deal with it.

Revision as of 19:20, 2 July 2022


Cooking

Doughs

See Doughs, batters, leaveners

Greenery

Trees, O2, CO2

Water

On hydration

Drinking slowly?

3 liters a day, or less?

Coffee

Alcohol

On bottled water

On filtering water

Demineralized and distilled water

Distilled water is (nearly-)pure H2O, because distillation means you move the water and leave behind most other things.


Demineralized water means few to no minerals (fresh natural water tends to have minerals in it e.g. due to limestone. Tapwater has more controlled bunch of these things; see also hard water)

...but says little about what else may still be in there -
it's useful to keep minerals out of clothes irons (which you want largely to avoid limescale), car batteries (which you want to avoid self-discharge and corrosion), and such.


On contents of demineralized water

Demineralized water often mentions it is not fit for consumption

in practice it's usually pretty clean water, but it's not guaranteed to be pure
largely because depending on the process of demineralization, there may be other things still left in there, say, a few bacteria. Your iron or car battery won't care, but you might
and because it doesn't matter for the intended uses
(also in part because it's also sold in supermarkets, so it's useful, possibly required, to point this out explicitly)


Does distilled or demineralized water lead to nutritional deficiency?

On water poisoning

This article/section is a stub — probably a pile of half-sorted notes, is not well-checked so may have incorrect bits. (Feel free to ignore, or tell me)

Most of your body contains something like 0.15% salt, and blood 0.9%.


Water poisoning happens when drinking a large amount in a short time, because of what it does to certain balances in your body, primarily salt and other electrolytes.


If you manage to dilute your body significantly, it starts affecting cellular function in general, which is the real problem.

If you manage to dilute your blood significantly, it's part of that mechanism that dilutes your body. This is the immediate intermediate thing you'ld want to avoid.


You will probably notice this poor function because it leads to headache, poorer muscle control, and possibly vomiting and diarrhea (possibly your body trying to correct things?{{verify}).

The fact that you will feel bad, and have probably associated "I feel bloated, I probably need to stop drinking water" is why most people are at negligible risk.

(though if you confuse it with "I'm dehydrated, I need to drink water", that's not great)


Time is a significant factor,

in part because your kidneys are happy to make you pee a lot more
so drinking a lot of water over a lot of time is dealt with
it wastes some salt in the process, but not very much(verify)
in part because because it takes a while for you to absorb water you drink, basically while it's in your gut
(related to why moderately fast rehydration in hospitals is done via saline IVs - it's in multiple ways more practical than drinking, which relies on timing and attention(verify)).

The time factor is why you see statements like "stay under 3-4 liters of water within in a few hours".


Doesn't distilled water do this a lot quicker?

No.

Quickly drinking liters of almost any water based drink will do this, basically because most water based drinks are almost entirely water.


Sure, tap water and bottled water has things beyond H2O, including sodium.

The concentrations of these (called its osmolality) are very low (order of roughly 0.003%(verify), so they matter more to the taste of the water and maybe being a mild supplement (these amounts are very low relative to the amounts we need).

e.g. for salt, it is primarily the salt we add to our food that helps us keep our salt balance, and your cravings will typically guide you to a decent amount of salt (actually, many of us get a little too much salt).


Basically, as long as the concentration of salt in this water is lower, it will lead to osmotic pressures between it and your body. (a.k.a. hypotonic)

The point is that both the maybe 0.003% in tap water and and 0.000% in distilled water is significantly lower than your body's 0.15% - one or two orders of magnitude. In a practical sense, both are so much lower that they have the same effect.



There's a difference you probably measure in lab conditions, but that's about it.

If you're stranded in a desert for weeks, and have the choice of what water to take, maybe, but still not really, in that it'd be a lot more important to catch the salt you sweat out.

And it might actually make a real difference what the non-distilled water is. If it's not regulated tap water, the possibility of pathogens may be a lot more important)


Water hardness

This article/section is a stub — probably a pile of half-sorted notes, is not well-checked so may have incorrect bits. (Feel free to ignore, or tell me)

Fluoride in drinking water

Salty water

Electrical resistance of water

See Electronics_notes/Resistors#Resistance_of_fluids

Oxyhydrogen