Salt Ice - surprising results

[team_mongo]

I while back some may recall a thread on salt for ice, and whether it lasted longer. I couldn't find a clear answer anywhere, so I did a little experiment.

4 1L identical sealed plastic bags
1. Pure water (not tap water)
2. 5% glucose
3. 0.9% w/w pure saltwater (ie pure water with NaCl - not table salt)
4. 3% w/w pure saltwater

Hung up out of the sun for 8 hours, and surface temperature measured with a laser thermometer.

Very interesting results
1. Heavy salt water, will maintain sub zero temps for longer.
2. After 7 degrees, heavy salt water warms quickly
3. After 7 degrees, pure water kept the lowest temperature for the longest!
4. Glucose water is useless.

[TheGurn]

Thanks Team_Mongo

That's pretty much what I wanted to try, but I don't have the gear.
It supports the info you gave in your previous posts.

So... Obviously it's nowhere near as effective as dry ice, but inside an efficient esky, salt ice 'should' keep fresh water ice 'solid' for just that little while longer, (if you ditch it soon after it melts)

Now I've just gotta play around with ratios of salt ice to fresh ice to see how much longer and if it's all worthwhile. :)

Cheers

Gurn

[Noelm]

I love experiments, it makes a lot more sense, (even if they are home science types of things that I usually do) than just people sprouting about "perhaps and maybe", or "I had a block od ice that lasted 3 weeks" it gives us a more or less definitive answer.

[murf]

thanks for that info :)

now can you go one step further and see what salt ratios to "fresh water Ice" to make the best Ice slurry?

as in who knows how to go about it?

1lt pure water ice to 1ltr seawater
1lt pure water ice to 1ltr seawater with extra salt added
etc

I know it gets bloody cold and will freeze coke cans and water bottles very fast

cheers Murf

[PinHead]

Alas the results are non conclusive..did you plot a pressure enthalpy chart for all the test substances..did you measure the external air pressure and humidity..they all have an effect on the outcome. Was the laser thermometer certified..so many chances they are way out of whack at any given time. But hell..good fun to do something like that.

[garman1]

Alas the results are non conclusive..did you plot a pressure enthalpy chart for all the test substances..did you measure the external air pressure and humidity..they all have an effect on the outcome. Was the laser thermometer certified..so many chances they are way out of whack at any given time. But hell..good fun to do something like that.


Wow I am going to google enthalpy charts to find out what that is but wouldn't the air pressure and humidity be the same on both bags? So the changes would be the same for both. The same for the laser, same laser so even if it was 5 degrees out, it would be 5 degrees out for both bags.

Anyway the info was good and the comments made me smile, enjoy the day everyone...............

P.S.

I googled enthalpy, wow now that looks complex...... I think I might send sheldon from "the big bang theory" an email to weigh in on this to help out, if nothing else sheldon would make everyone smile. :)

[pescados]

When fishing from a jetty ( salt water) I usually save some and fill up 2 or 3 litre plastc milk bottles
and freeze them.
When going fishing put one in the container to put fish in and add some salt water when on the spot.
Keeps cold for quite a long time.