How to calculate flash point of mixture?

  1. Hey guys,
    I would like to create a mixture out of two liquids with an ideal flash point of around 70ºF. The liquids I have to work with are 200 proof (100%) isopropyl alcohol (2-propanol) and aliphatic hydrocarbon mixture (aka hydrotreated petroleum distillates). What I'm looking for is the ideal ratio of alcohol to petroleum to mix in order to get a flash point close to 70ºF.

    So far, I have collected this info on the liquids:
    • Alcohol MSDS: goo.gl/bFnGg
    • Flash point: 53ºF
    • Petroleum MSDS: goo.gl/XWEKf
    • Flash point: 142ºF
    • Petroleum % by weight: 100%
    • Petroleum consists of hydrocarbons having carbon numbers predominantly in the range of C9 through C16 and boiling in the range of approximately 150.degree.C to 290.degree.C (302.degree.F to 554.degree.F).
      More info: goo.gl/eJvHK
      Search for "64742-47-8"

    Is there a formula I can use to go about doing this? Unfortunately, I only have a high school chemistry and physics background, so the farthest I have got is google :P

    Thanks,
    JGAN
     
  2. jcsd
  3. Hi, a precise calculation, based in thermodynamics, is quite involved. However, if you Google something like "Effect of Additives on the Flash Point of Flammable Liquid" you will find that you can begin by adding water to the alcohol to raise its flash point (for example, a mixture of .7 water & .3 methanol seems to raise the flash point by 25 degrees C). You would then add this mixture to the petroleum.
     
  4. One thing that makes this harder is whether the mixture will be 100% soluble or not- a two phase system is a strong possibility if even a slight amount of H2O contacts this, and then the vapor pressure exerted by the alcohol phase will rule the flashpoint as if the other was not even there.

    If higher alcohols are available and exert the proper polar solvency for the application you propose for the mixture, they will ensure complete miscibility, be less prone to water breaking the phases, and will have a better flash point. They would also be able to mod the flash point of isopropanol so some of that can be incorporated.
     
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