Reply
 
Thread Tools Display Modes
  #1  
Old 02-10-2019, 11:05 AM
Oly Oly is online now
Guest
 
Join Date: Jul 2002
Posts: 1,556
Antifreeze thought experiment

Let's say you have a pool of standing water and you pour some standard automobile antifreeze in it. Later on you notice a nontrivial layer of ice on top of the pool. My question is, is the antifreeze concentration in the remaining liquid now more or less the same as it was before, or is it greater (and thus providing greater antifreeze protection)?
  #2  
Old 02-10-2019, 11:17 AM
Chronos's Avatar
Chronos Chronos is offline
Charter Member
Moderator
 
Join Date: Jan 2000
Location: The Land of Cleves
Posts: 81,365
If the antifreeze is anything like alcohol (in fact, sometimes it is alcohol), then the remaining liquid will have a higher antifreeze concentration. This is in fact one method for fortifying alcoholic drinks: You leave some weak apple cider out on the back porch in winter, remove the ice in the morning, and end up with strong applejack.
  #3  
Old 02-10-2019, 03:19 PM
EdelweissPirate EdelweissPirate is offline
Guest
 
Join Date: Mar 2015
Location: Portland, OR USA
Posts: 309
I wasn’t aware of that trick—nifty! It’s reverse distillation!
  #4  
Old 02-10-2019, 03:29 PM
Frankenstein Monster Frankenstein Monster is offline
Member
 
Join Date: Apr 2004
Location: Europe
Posts: 643
If the antifreeze (ethylene glycol + water mixture) forms an eutectic then the concentration of antifreeze would be the same in the liquid and the solid.

I found this presentation where it says on page 14 that the mixture has an eutectic point at "just under" 60% ethylene glycol concentration and -50 degC (-58 degF).

There exist places in Canada where you could actually see this in practice.
  #5  
Old 02-10-2019, 03:54 PM
Northern Piper Northern Piper is online now
Charter Member
 
Join Date: Jun 1999
Location: The snow is back.
Posts: 28,247
Please don't try this experiment in real life, as antifreeze is poisonous. If a dog can along and drank it, it would not be good.
  #6  
Old 02-10-2019, 06:52 PM
Oly Oly is online now
Guest
 
Join Date: Jul 2002
Posts: 1,556
Thank you Chronos. Yes, I didn't think about it that way. That is the same way they make so-called ice beers.
  #7  
Old 02-10-2019, 07:09 PM
Dr. Strangelove's Avatar
Dr. Strangelove Dr. Strangelove is offline
Guest
 
Join Date: Dec 2010
Posts: 7,445
Ice crystallization does a remarkable job at displacing contaminants. I have a system for creating clear ice blocks, which works similarly to a lake freezing from the top down, and stopping before the entire thing is frozen. I wanted to make colored ice using food coloring. The result was that the top half froze into perfectly clear ice, and the bottom half was liquid water with twice the concentration of coloring.
  #8  
Old 02-10-2019, 07:30 PM
Melbourne Melbourne is offline
Guest
 
Join Date: Nov 2009
Posts: 4,563
Quote:
Originally Posted by Chronos View Post
If the antifreeze is anything like alcohol (in fact, sometimes it is alcohol), then the remaining liquid will have a higher antifreeze concentration. This is in fact one method for fortifying alcoholic drinks: You leave some weak apple cider out on the back porch in winter, remove the ice in the morning, and end up with strong applejack.
From memory:

The eutectic point for ethanol/water is somewhere around 95%. Water will freeze out, (with the ice gradually becoming more alcoholic), until the remaining liquid is around 90% ethanol. Then you'll start to get ethanol/water ice mixed with the water\ethanol ice. The last remaining liquid will freeze out as a 5% water solid.

For Antifreeze, ethylene glycol, a 50% solution will freeze out water until it gets to 60%. A 75% solution will freeze out glycol until it gets to 60%. I haven't seen the curve so I don't know how 'glcolic' the frozen water will be, or how wet the frozen glycol will be, or if there will be a mixture of the two kinds of ice or only one kind of ice.

Last edited by Melbourne; 02-10-2019 at 07:31 PM.
Reply

Bookmarks

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is Off
HTML code is Off

Forum Jump


All times are GMT -5. The time now is 05:22 PM.

Powered by vBulletin® Version 3.8.7
Copyright ©2000 - 2019, vBulletin Solutions, Inc.

Send questions for Cecil Adams to: cecil@straightdope.com

Send comments about this website to: webmaster@straightdope.com

Terms of Use / Privacy Policy

Advertise on the Straight Dope!
(Your direct line to thousands of the smartest, hippest people on the planet, plus a few total dipsticks.)

Copyright 2018 STM Reader, LLC.

 
Copyright © 2017