Sciencemadness Discussion Board

Open Container with Acid Solution and Vapor on Storm Windows

ZpLake - 13-11-2012 at 18:57

Growing many years ago in an Eastern European country I remember my mother installing a small open container with a liquid (solution of H2SO4 or HCl acid, I think) between outside and inside window sashes during winter. This was preventing accumulation of water vapor on glass of the outside sash.

Any comments on the matter? Was the liquid really acid solution?

I am looking for solution of removing water vapor on my storm windows now during winter.

Thank you.

zed - 13-11-2012 at 19:11

Take some Epsom Salt, dehydrate it by heating, take the dried salt, put it in a small plastic container, and place it between your windows.

Much less dangerous than acid. If it spills, you can wipe it up with a sponge.

A quart container of Epsom Salt (MgSO4-7H2O) will cost a couple of bucks at your local Grocery Outlet Store.

This has a good chance of solving your problem.

Siggebo - 14-11-2012 at 02:29

Yes, it probably was concentrated sulfuric acid. It used to be common practice in Sweden as well.

woelen - 14-11-2012 at 04:03

It was concentrated sulfuric acid, but definately not hydrochloric acid. The latter gives off corrosive fumes, which make the glass appear frosty.

ZpLake - 15-11-2012 at 18:13

Thank you all for the reply helping me with the solution.

I am curious, however, how does the chemical equation look that describes the process using both, H2OSo4 and MgSO4-7H2O, while absorbing the moisture? I haven't done it since my high school chemistry class - back in late 60thies.

woelen - 15-11-2012 at 23:16

MgSO4 + 7H2O --> MgSO4.7H2O

H2SO4 + H2O --> H3O(+) + HSO4(-)

The latter is a strong simplification, in reality more water will be absorbed and more water molecules will associate with the proton from the acid, i.e.

H2SO4 + nH2O --> [H(OH2)n](+) + HSO4(-)

In case of sulfuric acid the main reaction is the release of a H(+) entity from the strongly acidic molecule H2SO4. If you want to know more about this, then read some text about acid/base chemistry. This may be a nice starter: http://en.wikipedia.org/wiki/Acid%E2%80%93base_reaction

ZpLake - 23-12-2012 at 08:40

What quantity of the salt should be, in order to be effective in removing moister from the window glass?
What is more significant: open surface or quantity of the salt?
How do I dehydrate Epsom Salt (MgSO4-7H2O) in home environment?
Does it mean that once it absorbs moisture between the windows it has to be dehydrated again?

Would using H2SO4 solution, like in the old days, be less laborious than the above method, provided I know the required concentration that would work and the safety measures in handling the solution are taken? There are no kids in the house.

Thank you.

Hexavalent - 23-12-2012 at 09:28

Quote: Originally posted by ZpLake  
What quantity of the salt should be, in order to be effective in removing moister from the window glass?


Depends on the size of the window...I would use at least 500g to a kilogram for it to be effective, TBH.
Quote: Originally posted by ZpLake  

What is more significant: open surface or quantity of the salt?


Both. Ideally, you want as much of the salt as possible over as large an area around the window as is convenient.
Quote: Originally posted by ZpLake  

How do I dehydrate Epsom Salt (MgSO4-7H2O) in home environment?


Pop some of the hydrated stuff into a tray, and bake it in the oven for a few hours at around 150*C.
Quote: Originally posted by ZpLake  

Does it mean that once it absorbs moisture between the windows it has to be dehydrated again?


Yes. Once it has been fully used, you can dehydrate it in the oven and re-use it again.
Quote: Originally posted by ZpLake  

Would using H2SO4 solution, like in the old days, be less laborious than the above method, provided I know the required concentration that would work and the safety measures in handling the solution are taken? There are no kids in the house.


In short no. Once sulfuric acid has absorbed water, it is much harder and more dangerous to remove it again for future re-use. It is also usually much more expensive than MgSO4, and, even if you do know the correct procedures for handling it, spills can still happen. Trust me, a concentrated sulfuric acid spill is not much fun in any location.


[Edited on 23-12-2012 by Hexavalent]

Endimion17 - 23-12-2012 at 09:56

I think he's talking about putting the salt between the glass panels. There's no use of putting it in the room. People evaporate and would render the salt useless in a few days.

Hexavalent - 23-12-2012 at 11:01

Ah, I see - my apologies for the confusion.

Having said that, I have a small dehumidifier unit filled with CaCl2 next to my window which works very well at eliminating moisture building up during the night. I also once had one that said it contained CaO on the back: no prizes for guessing what I did with it :P

ZpLake - 23-12-2012 at 13:14

With all due respect to the answers, it does't appear practical to put 500 g between the windows space - outside and inside. The space is narrow - just 4 cm. Also, drying the salt for few hours all the time isn't a "convenience" either.

The dehumidifier suggestion won't work either - it wouldn't affect volume between the window. IN addition, the room air is very dry already - the heating is done by cast iron radiators.

I do not recall any instances of safety issue when in the old days concentrated H2SO4 method was used. As, SIGGEBO wrote "Yes, it probably was concentrated sulfuric acid. It used to be common practice in Sweden as well." The country I lived then, 50+ years ago, as I recollect a glass container with some acid liquid was installed in a winter between window sashes, was next to Sweden.

Endimion17 - 23-12-2012 at 15:28

Quote: Originally posted by ZpLake  
With all due respect to the answers, it does't appear practical to put 500 g between the windows space - outside and inside. The space is narrow - just 4 cm. Also, drying the salt for few hours all the time isn't a "convenience" either.

The dehumidifier suggestion won't work either - it wouldn't affect volume between the window. IN addition, the room air is very dry already - the heating is done by cast iron radiators.

I do not recall any instances of safety issue when in the old days concentrated H2SO4 method was used. As, SIGGEBO wrote "Yes, it probably was concentrated sulfuric acid. It used to be common practice in Sweden as well." The country I lived then, 50+ years ago, as I recollect a glass container with some acid liquid was installed in a winter between window sashes, was next to Sweden.


Just wanted to point out that the room air isn't dry if the heating is done by radiators. Its relative humidity is low, not absolute humidity, which is quite high during the winter because the windows are rarely opened and people tend to stay inside.

ZpLake - 23-12-2012 at 17:07

Endimion17,

Understood. I agree. However, drying that air even more would make living in the room uncomfortable. For start, the body skin would need to be moisterised.

I think, the best solution to the problem is to seal better inner sash, so the room air, even of the low humidity, doesn't leak toward the cold surface of the storm window glass. So, the current condensation would be reduced or eliminated.

Hexavalent - 24-12-2012 at 02:09

Not being funny, but why don't you just wipe the windows in the morning?

ZpLake - 24-12-2012 at 07:42

I would rather spend the same time drinking my coffee before going to work. It is most likely I would have to wipe the same windows, in different rooms - total 4-6 windows, in the evening again. In addition, the inner windows are sliding vertically, so it isn't possible to reach upper, facing in, area of the outside (storm) windows.