[gluedudeguru]

As a general rule of thumb, i was using a fairly logical formula to calculate flash point.  Essentially, take the conc. of each constituent and divide it by its flash point, sum these and put them under 100 and you get an accurate estimate.  Here is the real question.

When using an equation like this, what flash point should i assign water in a dilution.  Say a mix of 50/50 methanol?  Ethanol has a flash point of 13C, what would the flash point be for the dilution?

[Stepan]

I think the formula is wrong. Let say you have 10% "A" with Flash point around 10C, and 90% "B" with flash point 250C. I am sure the new flash point will be around 12C

[gluedudeguru]

http://www.uctm.edu/journal/j2006-3/04-Hristova-291-296.pdf

Bottom right corner of the fourth page is the formula i was describing.

For the scenario that you presented i would get a combined flash point of 73.53.

Is this beleivable when taking into account that flash points are not directly additive.

[Stepan]

Correct me if I am wrong. Formula #19 on page 4 (294) deals with Lower Flammability Limit in % units.

Beyond the formula. In general I agree that it should be a correlation between individual Flash Points of components and their mixture. But this correlation cannot be universal, and if developed would work for a given mixture only: let say for hydrocarbons, or alcohol-water mixtures.

What I was trying to say in my example: the most important factor for ignition would be concentration of flammable vapours in air. If you have two (or more) very different flammable liquids in a mixture, the most volatile one will likely be responsible for vapour concentration. And therefore the flash point of the mixture will be similar to flash point of the most volatile component (in mathematical form this is given in formula #2 of the article you quoted).   

[gale]

help please:  I have a flash point of 98.1F with 12 % ethanol and 48% water.  The rest are herbal or vitamin ingredients.   I want the flash point to be >100F
What blend will give me that?   9% alcohol?