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Ethanol Freeze Protected Water Solutions

Freezing temperature and flash points for ethanol based water solutions or brines.

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Ethanol based Water Solutions Freezing Point

Freezing Point
Ethanol Concentration
(% by volume)
Temperature (oF) 32 25 15 5 -10 -25 -35 -55 -75 -110 -175
(oC) 0 -4 -9 -15 -23 -32 -37 -48 -59 -73 -115

Flash Points of Ethanol based Water Solutions

The flash point of a chemical is the lowest temperature where it will evaporate enough fluid to form a combustible concentration of gas. The flash point is an indication of how easy a chemical may burn.

Flash Point
Ethanol Concentration
(% by weight)
Temperature (oF) 144 120 97 84 79 75 72 70 68 63 55
(oC) 62 49 36 29 26 24 22 21 20 17 13


  • HIGH flammability if pure

Ethanol water solution - freezing temperature and flash point chart

Download and print Ethanol Water Solution - Freezing Temperature and Flash Point chart.

Alternatives to Ethanol based Water Solutions

Example - Ethanol Concentration at Freezing Point at -20oC

By using linear interpolation between two known concentrations and their freezing points - the concentration at a third freezing point can be calculated as

CC = [(CB - CA) / (tB - tA)] (tC - tA) + CA                                (1)


C = concentration in ethanol - water solution

t = freezing point (oC, oF)

A, B = known freezing points 

C = calculated freezing point 

The ethanol concentration with freezing point at -20oC can be calculated by interpolating the concentration between freezing point -15oC and -23oC in the table above.

Cc = [((40 %) - (30 %)) / ((-23 oC) - (-15 oC))] ((-20 oC) - (-15 oC)) + (30 %) = 36.25 %

Note that this calculation is simplified by assuming that the concentration vs. freezing point follows a straight line. This not necessary correct.

If a 90% ethanol-water solution shall be mixed with clean water to achieve a freezing point of -20oC (ethanol concentration 36.25% (0.3625)) - the amount of added water can be calculated with volume balance - the amount of ethanol before mix is the same as after the mix:

C Vs = Cm (Vs + Vw)                                                        (2)


Vs = volume of the ethanol - water solution (liter, gallon)

Cm = concentration in mix

Vm = volume of mix (liter, gallon)

Vw = volume of the added clean water (liter, gallon)

Rearranging the equation to express the volume of water added to the mixture

Vw = (C - Cm) Vs / Cm                                                     (2b)

Substituting with values

Vw = (0.9 - 0.3625) Vs / 0.3625

     = 1.48 Vs

- for every liter 90% ethanol-water solution 1.48 liter of clean water must be mixed in to achieve an ethanol concentration of 36.25 % and freezing point -20oC.

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  • Engineering ToolBox, (2005). Ethanol Freeze Protected Water Solutions. [online] Available at: [Accessed Day Mo. Year].

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