chevyman454 & pontiacGP: The boiling point of water is increased by the addition of ethylene glycols AND pressure increase.
Ethylene glycol aqueous solutions DO have higher boiling temperature than water at the same pressure, but increasing pressure has a greater effect on boiling temperature than the addition of ethylene glycol, at least up to about 80% ethylene glycol by weight.
Freezing temperature is a different story. At atmospheric pressure, water freezes at 0C. A 50% ethylene glycol/water solution (generally recommended for automotive coolant) drops the freezing point to approximately -36C.
chevyman454: not sure where you got your data, but the boiling point of ethylene glycol at atmospheric pressure is approximately 368F, much higher than water at 212F.
Here's a link to a useful report on Ethylene glycol properties, both independently and in various aqueous solutions. This is a manufacturer's Product Guide (MEGlobal) for their Ethylene Glycol product:
http://www.meglobal.biz/media/product_guides/MEGlobal_MEG.pdf
This is also a case where Wikipedia has some good info. This is from the Wikipedia article on Ethylene Glycol:
Pure ethylene glycol freezes at about −12 °C (10.4 °F), but when mixed with water molecules, neither can readily form a solid crystal structure, and therefore the freezing point of the mixture is depressed significantly. The minimum freezing point is observed when the ethylene glycol percent in water is about 70%, as shown below. This is the reason pure ethylene glycol is not used as an antifreeze—water is a necessary component as well.
Ethylene glycol freezing point vs. concentration in water
Weight Percent EG (%) Freezing Point (deg F) Freezing Point (deg C)
0 32 0
10 25 -4
20 20 -7
30 5 -15
40 -10 -23
50 -30 -34
60 -55 -48
70 -60 -51
80 -50 -45
90 -20 -29
100 10 -12
However, the boiling point for aqueous ethylene glycol increases monotonically with increasing ethylene glycol percentage. Thus, the use of ethylene glycol not only depresses the freezing point, but also elevates the boiling point such that the operating range for the heat transfer fluid is broadened on both ends of the temperature scale. The increase in boiling temperature is due to pure ethylene glycol having a much higher boiling point and lower vapor pressure than pure water; there is no chemical stabilization against boiling of the liquid phase at intermediate compositions, as there is against freezing.
Ethylene glycol boiling point vs. concentration in water
Weight Percent EG (%) Boiling Point (deg F) Boiling Point (deg C)
0 212 100
10 215 102
20 215 102
30 220 104
40 220 104
50 225 107
60 230 110
70 240 116
80 255 124
90 285 140
100 387 197
HTH.
