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When snow melts, does the purest water melt first? Answered

I am intersted in purifying water through freezing. I know when you make ice cubes, the white cloudy stuff/minerals/solids gets frozen in the center and therefore is the last thing to thaw out back to liquid. I was wondering if that would be about what snow would do, or would it have to be a solid block of ice for that to work? I don't have a dissolved solids meter or I would test it myself. I'm pretty sure snow is fairly pure to start with, but I could be mistaken. It does have a taste to it. What is that taste?

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Codingpro (author)2018-01-08

Snow water will be all purified, and probably the center is the purest. None of the water will quench your thirst, though. Snow water doesn't have enough minerals in it to make it drinkable. If you use it for drinking water, it could flood your cells. that is why to always use a water purifier which adds particles to the water. River water is somewhat healthier then snows', in a way.

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iceng (author)2017-12-19

You do not have to melt it if you remove the pure outside ice while the migrated dissolved solids solvent center waits for a lower temp to freeze and gets drained before it does harden..

This center last to freeze happens so often in my fridge, I'm surprised it is not common knowledge..

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miked2001 (author)2017-12-19

The white clouds are air bubbles not minerals. That area melts last because it is the center of the cube.

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avocadostains (author)2017-12-17

This study looks relevant but I'm not quite grasping what it is saying, like most abstracts I try to read: http://pubs.acs.org/doi/abs/10.1021/jp8037686?jour...

Wow. you can read the summary but you have to buy the report. Craziness.

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There used to be web site run by friendly pirates at,

http://www.sci-hub.cc/

who were using some kind of site-license, or maybe other people's, or university's site-licences, for to let ordinary slobs (like you and me) download these kinds of papers, one at a time, by way of a web form.

I mean, I used it as recently as about a month ago, I think, but that url (www.sci-hub.cc) seems to be not working, at present, for me, today.

I hope they're OK, and their web site gets working again some time.

Oh, wait! The Wikipedia article for "Sci-hub" has their current working adress(es)

https://en.wikipedia.org/wiki/Sci-Hub

one of them is

https://sci-hub.la/

Yeah. So, go there, and feed the form you find there that funny url from pubs.acs.org, and hopefully that will work for you.

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Jack A Lopez (author)2017-12-17

The Wikipedia article for, "Fractional freezing",

https://en.wikipedia.org/wiki/Fractional_freezing


claims fractional freezing can be used to desalinate sea water.

"Fractional freezing can be used to desalinate sea water. In a process
that naturally occurs with sea ice, frozen salt water, when partially
melted, leaves behind ice that is of a much lower salt content. Because
sodium chloride lowers the melting point of water, the salt in sea water
tends to be forced out of pure water while freezing, called brine
rejection."

Although, it does not give any details on how well this works, or any links to references backing up this claim. I dunno. Also there are Wiki articles for "Sea ice", and "Sea ice growth processes", but I wasn't able to glean too much from these.


By the way, I think the reason you see impurities in the center of your ice cubes is because of the direction of the temperature gradient seen by the water while it is freezing.

What I'm saying is the walls of the tray are colder than the water in the center, so more pure water-ice freezes onto the walls of the tray first, and the impurities get concentrated into a little pocket at the center of the cube.

It is possible to make the temperature gradient go the other way; i.e. colder in the center, warmer on the outside.

There are ice machines that grow cylindrical ice cubes, in this manner, on chilled, cylinder shaped forms, that are colder than the surrounding water.

Also, I think, the temperature distribution inside a Czochralski furnace,

https://en.wikipedia.org/wiki/Czochralski_process
is roughly the same shape; i.e. colder in the center, warmer on the outside, and with temperature distribution that is radially symmetric.

And I am guessing the same thing happens with impurities in the Czochralski process; i.e. those get left in the liquid surrounding the colder cylinder in the center.

Also I wanted to give you a Youtube link that includes some images of one of these ice machines that grows cylindrical ice cubes, on stubby cylindrical forms, in case you had not seen this before.

Also, another thing I was going to mention, I think the Wikipedia article for "TDS meter",

https://en.wikipedia.org/wiki/TDS_meter

answers one of your questions about non-conductive, dissolved impurities in water,

"Dissolved organic solids, such as sugar, and microscopic solid particles, such as colloids, do not significantly affect the conductivity of a solution, and are not taken into account."

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iceng (author)2017-12-15

Most dissolved materials form ionic solutions which affect conductivity and that can be measured with an ohm meter... Sugar does not for ionic solutions !

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avocadostains (author)iceng2017-12-17

But the gases do then increase conductivity? Is what you're saying?

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avocadostains (author)iceng2017-12-17

Sugar does not act as a conductor in water?

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Toga_Dan (author)2017-12-16

stuff disolved in ice makes it thaw sooner. Think of salt.

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avocadostains (author)Toga_Dan2017-12-17

Yea, but does the 'stuff' melt out first or the pure ice?

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iceng (author)2017-12-16

If you are freezing water you can save a lot of effort by taking out the cubes when they freeze outside but the center is still liquid... Keep the ice, and drain the water..

Repeat the process until it gives clear solid...

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avocadostains (author)iceng2017-12-17

That makes a lot of sense to me. Youd have to try it with real dirty water to see if it works. I'll try it next time it freezes. I guess I could do the same thing with snow. Melt some snow and see if the first half is cleaner or the second half. Now that I think about it. I think the second half would be cleaner, because when you eat a snow cone, the dye and flavor is the first thing to melt out and the pure ice is left. I think you may have it backwards. But then again, I might be thinking along the same lines as 'sound travels faster than light because when you turn the tv on you hear it first and then see the picture. Well, it's my question. I guess I better set up some snow melting experiments. Whatever is in snow, its in rainwater too, because they taste the same. but snow water is stronger than rain water in taste.

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rickharris (author)2017-12-16

It makes much more sense to distill water in a conventional manner using heat. More controllable, more energy efficient, and more easily available equipment.

I have however freeze distilled alcohol which works quite well.

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avocadostains (author)rickharris2017-12-17

I have distilled water with a distiller I built at home out of a stock pot with a lid, a bunch of clamps, and a flexible copper coil. It was about the best water ever. You have to be careful because it easily absorbs flavors from the mineral left behind after the water boils down. You have to keep it at the same level for best results which I never figured out how to do.I was thinking some setup like an automatic dog watering bowl. one time i put a bunch of pennies in the bottom to help transfer hest since it was a cheap, thin stainless steel stock stockpot which does not transfer heat well. The full simply would barely simmer even on full heat no matter how long I left it on for. Anyways, the resultant water tasted nasty like dirty pennies even though it was vapor distilled. Go figure. Thats interesting about the ethanol. I made apple jack one time in my backyard that way. It smelled strongly of alcohol but i didn't drink it. Every time I freeze distilled it I seemed to lose more alcohol and it didnt seem to get any stronger. I dont know what I did wrong..

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Jack A Lopez (author)rickharris2017-12-16

It is not obvious to me that distillation will cost less energy than crystallization.

I mean, just from looking at Wikipedia's data page for water, the enthalpy per mol needed to melt water (6.0 kJ/mol), is a lot less than the enthalpy per mol needed to vaporize water (41 kJ/mol), and I think both those numbers refer the usual Terrestrial, laboratory conditions; i.e water melting at 0 C, and boiling at 100 C, under 100 kPa, or 1 atm, of surrounding pressure.

https://en.wikipedia.org/wiki/Water_(data_page)

I think there is bias in your answer; i.e. you think distilling water will be the preferred method, just because it is a familiar method.

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Toga_Dan (author)2017-12-16

The ice block idea is interesting. would scraping the surface yeild pure water? Dunno. There oughta b a low tech way to test.

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avocadostains (author)Toga_Dan2017-12-16

There is. Thanks for getting me thinking. I believe that pure water is less conductive than water with minerals/solids added. So if you had a voltage meter, which I do, I suppose I could make a test that way. You can also get a dissolved solids meter off ebay for under 20 bucks. Neither solution is low tech, but both are low cost. As for low tech, I suppose I could boil the water in a glass pot and see what remained in the pot. My grandpa always set a bot of well water on top of his wood stove and never washed it. The crust inside of the pot grew to be about an inch thick over the years.

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avocadostains (author)rickharris2017-12-16

Wow! That is amazing technology. Does not rely on heat. You can basically make sup concentrated food for easy transpot with damaging their nutrient profile. Thanks for the vid!

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Downunder35m (author)2017-12-15

I think it is not that easy...
Water does not act normal anyway for starters.
Then, as you alrady figured out it also freezes differently depndin on temp and impurities.
So under ideal conditions you could freeze water so te impurities are trapped on the inside with very little on the outer shell.
But snow is water that crystalises around a seed.
This seed can be a smaller piece of ice, dust, a mineral...
In an area far away from civilisation and winds in your favour you can get quite pure snow but it still leaves whatever comes with the water itself.
Take ice core drilling.
The ice was snow at some point and is now used to check whatever we had in the atmosphere at the time of formation.
If you search for images online you will see the endless shades of white.

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iceng (author)2017-12-15

Pure water is most undesirable in fact corrosive and dangerous..

Certain atmospheric dissolved gases in water are what makes nice drinking water..

In fact a sufficient volume of CO2 Carbon Dioxide dissolved in water is responsible for effervescence as in fizzy drinks..

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avocadostains (author)iceng2017-12-15

That makes sense. I would assume then that water purified by steam distillation would have dissolved atmospheric gases in it whereas reverse osmosis water and tap water would not som much. Perhaps that is why plants respond so much better to rain water than to water from a garden hose. I would assume the dissolved gases are good for people too. I'm just thinking about pollution in snow from exhaust. I don't know how much of an issue that is. Probably no more so than sitting in traffic and breathing the air. Thanks for the answer!

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