Sciencemadness Discussion Board
Not logged in [Login ]
Go To Bottom

Printable Version  
Author: Subject: Does excess hydrochloric acid evaporate?
Jacob
Harmless
*




Posts: 23
Registered: 7-4-2019
Member Is Offline


[*] posted on 12-5-2020 at 07:15
Does excess hydrochloric acid evaporate?


Lets say you neutralize a base (eg NaOH) with excess HCl then put it on a heater to evaporate the water to dry. Does excess HCl go away too, or do you get acid contaminated salt?
View user's profile View All Posts By User
mackolol
National Hazard
****




Posts: 399
Registered: 26-10-2017
Location: Poland
Member Is Offline

Mood: Psychedelic

[*] posted on 12-5-2020 at 07:29


It evaporates too and I would even say that first, because HCl is a gas dissolved in water (in this case). It doesn't form complex with alkali salts, but with some salts of heavier metals it forms complexes, although they're quite thermally unstable, so you can get rid of it by heating.
View user's profile View All Posts By User
Jacob
Harmless
*




Posts: 23
Registered: 7-4-2019
Member Is Offline


[*] posted on 12-5-2020 at 08:05


Quote: Originally posted by mackolol  
It evaporates too and I would even say that first, because HCl is a gas dissolved in water (in this case). It doesn't form complex with alkali salts, but with some salts of heavier metals it forms complexes, although they're quite thermally unstable, so you can get rid of it by heating.


Thanks for the reply!

I figured if heating removes water from hydrated salts, it will do for HCl, too. I will report back the result for a diamine dihydrochloride salt. The solution is quite acidic right now.
View user's profile View All Posts By User
Tsjerk
International Hazard
*****




Posts: 2291
Registered: 20-4-2005
Location: Netherlands
Member Is Offline

Mood: Mood

[*] posted on 12-5-2020 at 09:08


It will evaporate, but it will first concentrate to about 20 percent. HCl and water like each other quite a lot.

Not all compounds like 20% hydrochloric acid.
View user's profile View All Posts By User
woelen
Super Administrator
*********




Posts: 7284
Registered: 20-8-2005
Location: Netherlands
Member Is Offline

Mood: interested

[*] posted on 14-5-2020 at 02:49


If you have an amine HCl salt or an ammonium salt, then only the really excess HCl will evaporate. If you e.g. mix excess hydrochloric acid with a solution of methyl amine, then you get methyl ammonium chloride in solution, with excess HCl. On evaporation, water and HCl are released, and methyl ammonium chloride remains behind. Do not expect the appearance of free emthyl amine again.



The art of wondering makes life worth living...
Want to wonder? Look at https://woelen.homescience.net
View user's profile Visit user's homepage View All Posts By User
mayko
International Hazard
*****




Posts: 1063
Registered: 17-1-2013
Location: Carrboro, NC
Member Is Offline

Mood: anomalous

[*] posted on 14-5-2020 at 07:14


Be aware that HCl vapors will find and rust every piece of iron and many of steel in its wake - do this outside/with good ventilation!



al-khemie is not a terrorist organization
"Chemicals, chemicals... I need chemicals!" - George Hayduke
"Wubbalubba dub-dub!" - Rick Sanchez
View user's profile Visit user's homepage View All Posts By User
Jacob
Harmless
*




Posts: 23
Registered: 7-4-2019
Member Is Offline


[*] posted on 14-5-2020 at 11:14


Quote: Originally posted by Tsjerk  
It will evaporate, but it will first concentrate to about 20 percent. HCl and water like each other quite a lot.

Not all compounds like 20% hydrochloric acid.


Gotcha. HCl and water form an unusual 20% azeotrope that boils at 110°C. I set the heater slightly higher.
View user's profile View All Posts By User
Jacob
Harmless
*




Posts: 23
Registered: 7-4-2019
Member Is Offline


[*] posted on 14-5-2020 at 11:17


Quote: Originally posted by woelen  
If you have an amine HCl salt or an ammonium salt, then only the really excess HCl will evaporate. If you e.g. mix excess hydrochloric acid with a solution of methyl amine, then you get methyl ammonium chloride in solution, with excess HCl. On evaporation, water and HCl are released, and methyl ammonium chloride remains behind. Do not expect the appearance of free emthyl amine again.


Thanks, that's a relief. Ethylene diamine dihydrochloride here.

Water is such a pain in the ass to get rid of. I will avoid it in the future and use alcohols and ethers if possible. They evaporate quickly and cleanly.

[Edited on 14-5-2020 by Jacob]
View user's profile View All Posts By User
unionised
International Hazard
*****




Posts: 4463
Registered: 1-11-2003
Location: UK
Member Is Offline

Mood: No Mood

[*] posted on 14-5-2020 at 11:18


20% isn't some magical number, fixed for all time and all circumstances.
It's roughly the azeotrope concentration if there isn't anything else present and at 1 atmosphere pressure.
And much the same is true of 110C.
View user's profile View All Posts By User
Jacob
Harmless
*




Posts: 23
Registered: 7-4-2019
Member Is Offline


[*] posted on 14-5-2020 at 11:22


Quote: Originally posted by mayko  
Be aware that HCl vapors will find and rust every piece of iron and many of steel in its wake - do this outside/with good ventilation!


I've had this accident before with a leaky HCl bottle. Never again! That's why I set up an ammonia solution spill nearby for a free smoke show.

Call me crazy.
View user's profile View All Posts By User
Jacob
Harmless
*




Posts: 23
Registered: 7-4-2019
Member Is Offline


[*] posted on 14-5-2020 at 11:25


Quote: Originally posted by unionised  
20% isn't some magical number, fixed for all time and all circumstances.
It's roughly the azeotrope concentration if there isn't anything else present and at 1 atmosphere pressure.
And much the same is true of 110C.



This place is high. Air is about 0.85 bar.
Doesn't matter anyway. I wanted it gone.
View user's profile View All Posts By User
unionised
International Hazard
*****




Posts: 4463
Registered: 1-11-2003
Location: UK
Member Is Offline

Mood: No Mood

[*] posted on 14-5-2020 at 13:46


Quote: Originally posted by Jacob  
Quote: Originally posted by mayko  
Be aware that HCl vapors will find and rust every piece of iron and many of steel in its wake - do this outside/with good ventilation!


I've had this accident before with a leaky HCl bottle. Never again! That's why I set up an ammonia solution spill nearby for a free smoke show.

Call me crazy.

Ammonium chloride smoke is also corrosive to metals.
View user's profile View All Posts By User

  Go To Top