I have a gallon of hardware store hydrochloric acid that I bought almost a year ago. It is labeled as "20 degree baume` 31.45% by weight" whatever
that means. I have not yet used it all up but I have noticed something interesting. It appears that over time it has possibly increased in
concentration. I am lead to believe this because when I first bought it and opened it there wasn't a whole lot of fumes. But now when I open it up it
fumes like crazy, it almost makes a small cloud around it self of hydrogen chloride gas. Has anyone heard of this happening? If it is really
self-concentrating I can't think of a mechanism for it. plante1999 - 29-6-2012 at 12:07
You simply opened the bottle when the weather was warmer than when you bough it, humidity have also an effect.cobalt_catalyst - 29-6-2012 at 12:21
You simply opened the bottle when the weather was warmer than when you bough it, humidity have also an effect.
That's what I initially thought, but it was the summer of last year that I bought it. So the temperature was pretty much the same then as it is now.BromicAcid - 29-6-2012 at 12:30
You used some, correct? Now you have more headspace in the bottle which allows for the accumulation of more 'fumes' and HCl to escape the solution.
It also gives a larger area for the mixing of gasses where the humidity from the air can come in an interact with the HCl to give a cloud upon
pouring.99chemicals - 29-6-2012 at 12:49
I have had that happen to me but never thought twice about it. It did not fume when I first used it but after using around 300 mls in some
experiments I opened it again and it fumed like crazy!. If you still think it concentrated do a titration.Poppy - 1-7-2012 at 15:10
I think if you leave for a couple years the jar may explode as it would be filled with pure HCl gas :O
jk
Well.. the older nitric acids I first tried seemed to smoke some more, but Haha Well I can't even sense the smell anymore!!1!woelen - 1-7-2012 at 22:32
Hydrochloric acid certainly does not "self-concentrate" when its concentration is above appr. 20% by weight. It goes the other way around, its
concentration gets lower over time if it is not stored in a well-sealed bottle. HCl forms an azeotrope with water and at appr. 20% HCl, the azeotropic
mix evaporates. At lower concentration, the percentage of water in the vapor is higher than in the liquid and then there will be slow increase of
concentration if the liquid evaporates. At higher concentration there will be more HCl in the vapor and hence the concentration becomes lower while
more of the liquid evaporates.
