Extending an exploration of windshield washer-fluid choices to freezing points of methanol-water mixes, all web-sources located agreed to within a couple of degrees from 0-60% w/w, yet above this proportion (and below 100%), repeatedly came across conflicting data (which fell into three groups). (Yes, the disagreements are all outside the range of winter driving on this planet - except perhaps for around Vostok Station...)

w/w various graphs by eye various tables engineering toolbox table all˚C
60% - 71 - 71 - 71 ˚C
70% -102 -137 - 82 ˚C
80% -116 -143 - 87 ˚C
90% -108 -146 - 90 ˚C
100% - 96 - 98 - 98 ˚C

examples of sources for above data:

http://www.methanol.org/wp-content/uploads/2016/06/FreezingPointsMethanol-WaterSolutions.pdf graph
https://patents.google.com/patent/WO2011153147A1/en table (~ 1/3 way into the document) https://www.engineeringtoolbox.com/methanol-water-d_987.html table

Thanks for any comment.

  • 2
    $\begingroup$ Different source data, different data processing, different errors made. $\endgroup$
    – Poutnik
    May 5 at 7:07
  • 1
    $\begingroup$ Thanks. Your emphasis on "different" inspired a new search strategy which led to a satisfactory answer to the question. $\endgroup$
    – revans19
    May 6 at 6:43

From Solid-Liquid Phase Diagram of the System Methanol-Water by G. A. Miller and D. K. Carpenter in J. Chem. Eng. Data 1964, 9, 3, 371–373 (July 1, 1964) [https://doi.org/10.1021/je60022a017]

"A solution of methanol and water that is methanol-rich tends to form a glass when cooled below the melting point. The liquid is very viscous at such temperatures (below -100° C.) because of the presence of hydrogen-bonded polymers. Because it is difficult to induce crystallization, the melting point is determined from a warming curve. Much of the wide divergence of melting point data for the composition range of 55 to 95 mole per cent* methanol results from the use of cooling curves."

* by a back-of-a-napkin calculation (assuming 32.042 g/mol MeOH and 18.015 g/mol H2O) the mole percentage mentioned is approximately 68% to 97% methanol (w/w).

Further - successful - online research was inspired by a comment; it appears the failure to find information with common search terms was due to a language difference. It seems specialists (presumably physical chemists) use "solid-liquid equilibrium" or "solid-liquid phase diagram" in documents which may completely exclude the term "freezing-point" - such as the publication quoted above which answers the original question.


Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.