[Recoil Rob]

I have a fluid that I know to be a mixture of propylene glycol (C₃H₈O₂) and distilled water (H₂O) but I do not know the percentage of PG except that it is less than 50%.

PG has a boiling point of 370.8˚ F, distilled water, 212˚ F.

My premise is if I take 100 cl of this mixture and put it on the heat the water would boil off first at or close to 212˚. Then the temp would begin to rise until it reached 370.8˚ at which time the PG would start to boil off.

If I start with 100cl and stop when the temp starts to rise, before the PG starts to boil, I should be left with only PG and will be able to determine what the ration is?

Is this a viable test?


thanks,

 Rob (who took chemistry in high school 1970-71) but still has a science mind.

[Borek]

Single distillation never yields pure product.

If there is an azeotrope, you will never get pure product.

Fastest approach would be to measure density of the solution and read the composition from tables.

[Recoil Rob]

Thank you for the reply.

So, I would need to get the weight of, let's say, 100 cc of the fluid and figure the density of the mixture?

PG's molar mass is  76.09 g mol⁻¹, it's density is  1.036 g/cm³.

Water's molar mass is  18.01528(33) g/mol,  it's density  is 0.99820 g/cm3 at 20 °C (room temp).

What formula will I be using to determine % of each solution?

And should I be asking this be in a physics forum?


thanks,

 Rob

[Borek]

What formula will I be using to determine % of each solution?

Not formula: tables exist, and you have to use them to check the solution composition.

This approach assumes solution is reasonably pure (doesn't contain much of anything else).

[Recoil Rob]

Thanks, that sound easier than doing the math. Where do i find the tables or what should I Google?


thanks,

 Rob

[Borek]

I would try to google using words like propylene glycol, solution, density, water, aqueous, perhaps solution.

There is a table built into concentration calculator - if you need the answer just once, or twice, free 30 days trial will easily cover your needs.

[Recoil Rob]

thank you for your help.