why the pH of a solvent is increasing when it is distilled?

Question

We are distilling mother liquiors from centrifuge of pharma filtrate
While distilling this to seperate the solvent we are facing the pH problem . The pH of the distilled is more than the pH of the Mother liquor .For example if the mother liquors pH is 3 then we are getting distilled pH nearly 7

We are distilling mother liquiors from centrifuge of pharma filtrate
While distilling this to seperate the solvent we are facing the pH problem . The pH of the distilled is more than the pH of the Mother liquor .For example if the mother liquors pH is 3 then we are getting distilled pH nearly 7 . Our aim is not to get distilled water but some other solvents in mixture

Answer 1

pH = -log[H+]
Your mother liquor probably has an organic acid like acetic acid. Distillation is just a method of separation of miscible solvents. One component probably has a natural pH of close to 7, like water. The other component probably has a lower pH.

Answer 2

This happens because when it is distilled the substances that make the liqour acidic(since the pH is below 7) are removed.However the pH won't increase beyond 7, as every substance becomes nuetral when it's pH is almost 7.Moreover if you take an alkaline substance(substances with pH value more than 7) and distill it then the pH value drops until it reaches 7.

Answer 3

It sounds like you're loosing some other components when distilling... are you collecting your fractions efficiently?

If you're loosing alcohol the pH would decrease, but not that much - another possibility is that the heating is causing some thermal breakdown of components in your mixture, and yet another is that the composition of dissolved gasses is altering the solution pH...

cheers,

Answer 4

As others have mentioned, you obviously have some volatile pH-controlling compounds that are being distilled.

Although pH 3 is pretty low, I wouldn't be surprised if you had a CO2/carbonate buffer system hiding in there. It's solubility will decrease quickly with heating.

Answer 5

you're distilling out the stabalizers. you're gonna have to figure out what is in the mother liquid that keeps the pH where you want it and either add it to the distillate or figure a way of separating that won't kill it

Answer 6

because you're eliminating other components through distillation. you'll end up with distilled water upon distillation. for liquor concerns, try using stabillizers before distillation.