Crypto - 16-1-2015 at 07:44
Steam can carry some compounds with it. That's steam distillation... What if I distill alcohol from water, when such compound are also present? A few
percents of water is distilling along with alcohol. Does this water still carry compounds with it or will that begin to happen when all of the alcohol
will be distilled off?
macckone - 16-1-2015 at 08:00
Yes, it carries compounds over.
The steam aspect doesn't really play into it.
Fulmen - 16-1-2015 at 08:22
As long as it has a vapor pressure it should be distilled over to some degree. IIRC a mixture of immiscible liquids will boil at the sum of it's vapor
pressures.
Nicodem - 16-1-2015 at 10:43
No, steam distillation is only possible when you distil from a biphasic mixture. Alternatively, compounds can also be carried over, if they form
azeotropes. The two are different phenomenons.
For example, if you distil a monophasic mixture of eugenol, ethanol and water, no steam distillation will occur. The content of the carried over
eugenol will correspond to a normal distillation (Raoult's law and its deviations). At the point where the mixture breaks to two phases, a steam
distillation effect comes into play (sum of partial pressures of components of each phase).
On the other hand, if the compound forms a low boiling azeotrope with water, it will be carried over even when you try to prevent it by employing a
distillation column of any given efficiency. For example, if you distil a mixture furfuryl alcohol and water, the amount of carried over furfuryl
alcohol will always be higher than what you would get by Raoult's law.