Ethylene Glycol Freezing Point with Water

[subtechy]

Hi all,
I have a query regarding the characterisitics of Ethylene Glycol when diluted with water. Apologies in advance if there is a simple explanation to this, I have a mechanical background and chemistry was never really my strength.
We regularly use glycol for pressure testing with water offshore to prevent the formation of potential hydrates in gas wells. It has only come to light (this afternoon) that the reason we use a 60/ 40 mix (EG to Water) is because this is the best concentration that can be achieved with regard to temperature. Upon looking into this, all the graphs I have seen back this up (all though the best seems to be 70/30). A higher concentration of EG will actually freeze at a higher temperature.

Can anybody explain this strange anomaly???

Kindest regards

M

 

[Unotec]

Check this out

http://www.engineeringtoolbox.com/ethylene-glycol-d_146.html

I think you might have an error in your assumption

<<A good friend will bail you out of jail, but a true friend
will be sitting beside you saying ” Damn that was fun!” - Unknown>>

 

[subtechy]

This was one of the sites I looked at yesterday and lo and behold, there is no temperatures given for above a 60% concentration. I have attached a table and graph I downloaded and plotted yesterday that shows the trend after a 70% concentration.

 

[katmar]

A mixture that behaves that way is called a eutectic mixture. If you seriously want to know why it behaves like that you can Google it, or start at

http://en.wikipedia.org/wiki/Eutectic

It's far too long ago that I studied this stuff for me to be able to give you a decent explanation, but it is all to do with intermolecular forces between like and dissimilar molecules varying with concentration. You get similar behavior with boiling points, but those mixtures are called azeotropes.

Katmar Software
Engineering & Risk Analysis Software

http://katmarsoftware.com

 

[subtechy]

Thats excellent, that has certainly pointed me in the right direction for doing some reading.

Many thanks

 

[Unotec]

Wow, I have seen a similar effect with acetic acid in water, but I always assumed glycol to be straight forward.
I stand corrected and learned something new.

<<A good friend will bail you out of jail, but a true friend
will be sitting beside you saying ” Damn that was fun!” - Unknown>>

 

[unclesyd]

About all your ever want to know about EG courtesy of Technology Lubricants.

http://www.technologylubricants.com/Technical/norkool_heat_transfer_fluid.pdf

I would file this information if the data is of any value to you.

 

[subtechy]

Many thanks, some great information here for future reference.