Difference between revisions of "Chemistry of common things"

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==On water poisoning==
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]].
Most of your body contains something like 0.15% salt, and you don't want it to be a lot lower or higher.
(your blood is 0.9% salt, because it's a big part of regulating salt levels)
Water poisoning refers to managing to dilute your body significantly,
because that starts affecting cellular function in general, which is the real problem.
In the more immediate sense, dilute your ''blood'' significantly leads to this, because your body can't regulate it anymore.
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 that tends to make people safe
: in part because your kidneys are happy to make you pee a lot more
:: so drinking liters more than you need ''over a day'' is much less of an issue than doing so within an hour
:: peeing that much 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
:: {{comment|(related to why moderately fast rehydration in hospitals is done via saline IVs - in seveeral ways it's more practical than drinking as that 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".
Drinking a lot of water means shifting various balances, basically diluting various things with water containing little else, and doing that enough causes effects like osmosis taking necessary salts out of your kidneys{{verify}}.
'''Doesn't distilled water do this a lot quicker?'''
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 H<sub>2</sub>O, including sodium.
Yet the concentrations of these (called its [https://en.wikipedia.org/wiki/Molality#Osmolality 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 - in particular for salt it's the salt we add to our food that keeps that balance).
The point is that both the maybe 0.003% in tap water and and 0.000% in distilled water are ''both'' are so much lower (one or two [[orders of magnitude]]) that they are both hypotonic, and have roughly the same osmotic effect on your body.
There's a difference you can 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)
'''Is sports drink a lot better?'''
When they say isotonic, the non-water component is usually ''primarily'' sugar,
not salt, so in terms of salt is still hypotonic.
This makes sense, for a few reasons. Among them:
* when you also drink it for energy, it would easily lead to getting too much salt.
* It's useful to counteract a little salt you lose via sweat, but it turns out the amounts are so low that you need a tiny amount to do so[https://pubmed.ncbi.nlm.nih.gov/26841436/].
: If your sweat is unusually salty, that's often an indication that your levels are overly high already, so not an indication you should replace it, but that you should ''reduce'' your salt intake.
'''So could you drink endless amounts of saline solution?'''
Much more of it

Revision as of 16:39, 6 August 2022



See Doughs, batters, leaveners


Trees, O2, CO2


On hydration

Drinking slowly?

3 liters a day, or less?



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

...(unlike fresh natural water, which 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?

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)

Hard water refers to water having relatively high mineral content.

Since we're usually talking about fresh water we want to use as drinking water, we are typically focusing on calcium (also magnesium) which comes naturally from the water source passing through limestone, chalk, gypsum, or such. Which gives you things like calcium and magnesium carbonates, bicarbonates, and sulfates.

High is relative - for calcium we're talking talking parts per million, where

soft water is on the order of 30ppm,
hard water on the order of 150ppm.
you get something like 700ppm in a few places

Many other things can qualify for 'mineral content', but typically the amounts are very small, and/or their appearance is local. (e.g. iron, aluminium, manganese)

Salt is one, in that seawater is technically very hard (6000+ ppm) due to its salt, but since it doesn't evaporate, this doesn't apply to fresh water.

Would you prefer soft or hard water?

It's a few different practical considerations, and none of them are hugely important - and the mentioned effects are frequently overstated.

Arguments for softer:

  • aesthetic:
    • softer water deposits less scale in showers, drinking glasses, and such
  • cost
    • softer water deposits less limescale in washing machines, kettles, which can make them last longer (thick scale makes heating less efficient and in extreme cases causes overheating)
    • soaps lather more, and you need less detergent (or separate water softener) - can be overstated since many contain softeners anyway
    • harder water is less ideal for some industrial processes (and needs fewer additives)
    • with soft water, washing clothes wears the fibers a little less

Arguments for harder:

  • softer water will pull out metal out of pipes over time, corroding unlined metal pipes more quickly
(more of a net end effect - there are a handful of other factors on corrosion speed)
which means water infrastructure can be cheaper to run, particularly that infrastructure is currently older, cheaper pipes.
  • Harder water could be considered a dietary supplement
though this is frequently overstated. The difference from this switch stays is from 'tiny' to 'small' on your calcium needs, and you need to get your minerals elsewhere anyway.

Arguments for either

  • "this water tastes nicer" - you probably prefer what you're used to


See also:

Fluoride in drinking water

Salty water


Electrical resistance of water

See Electronics_notes/Resistors#Resistance_of_fluids