LD5050 - 11-5-2017 at 18:50
I used H2SO4 to dry HCL gas by bubbling the HCL through the H2SO4 in a gassing setup. I was wondering if the H2SO4 is Still good to be used for other
things or is it not contaminated with HCL? If so how could I purify it again..distillation?
JJay - 11-5-2017 at 19:32
As long as the water concentration is low, sulfuric acid doesn't absorb HCl very easily, and any that does get absorbed will have trouble ionizing. If
you remove the water, I think the absorbed hydrogen chloride will evaporate.
Sulaiman - 11-5-2017 at 23:16
The hotter the H2SO4 the more rapidly the HCl will evaporate,
if you boil the H2SO4 , HCl then H2O will boil off
purifying then concentrating the H2SO4.
CAUTION: Clouds of corrosive, choking acid vapours will be generated
and if you concentrate the H2SO4 to near azeotropic it is quite scary due to the >330 oC stress on the glassware
and the potenial reaction of boiling concentrated sulphuric acid with eyes/skin etc.
ave369 - 13-5-2017 at 10:19
In one of my experiments I was distilling HCl off such a mixture (~90% H2SO4 + HCl gas). I've got an interesting result: not all of HCl exited as gas,
some exited as azeotropic hydrochloric acid that condensed in the condenser, and the sulfuric acid became more concentrated. I didn't measure the
temperature but I think it distilled off at a lower temp than water usually boils off ~90% H2SO4. Is such a thing possible?
elementcollector1 - 13-5-2017 at 10:37
Azeotropic hydrochloric acid, if I remember correctly, has a boiling point of 109 degrees Celsius. So, it's definitely possible. I would imagine that
in your setup, both the water and HCl gas were boiled off and subsequently recombined once the local temperature was cooled to 109 degrees (e.g. in
the condenser, as opposed to the boiling flask), while some water was presumably lost as vapor.