Sciencemadness Discussion Board

H2SO4 Crystallizing

Guest - 12-6-2013 at 21:55

I have a 500ml glass bottle with a ground glass stopper that is around 3/4 full of 98% H2SO4, It's been sitting there for a good 3-4 years now and I noticed that there are crystals forming around the stopper, is this normal? What would the crystals be?

H2SO4 is from unused battery electrolyte that was boiled down if that helps at all.

Hockeydemon - 12-6-2013 at 23:22

Quote: Originally posted by Guest  
I have a 500ml glass bottle with a ground glass stopper that is around 3/4 full of 98% H2SO4, It's been sitting there for a good 3-4 years now and I noticed that there are crystals forming around the stopper, is this normal? What would the crystals be?

H2SO4 is from unused battery electrolyte that was boiled down if that helps at all.


It is most likely sulfation which is a common battery deterioration. Did you perform a titration to determine it's concentration? If not then it is likely it is less than 98% pure, and has contaminants from the battery.

Guest - 13-6-2013 at 00:06

It was never in a battery, went straight from the bottle it was purchased in into a beaker, boiled until it reached over 330C and then poured into the bottle it's in now.

phlogiston - 13-6-2013 at 02:14

Is it sitting near a bottle of ammonia or an ammonia salt?

Pulverulescent - 13-6-2013 at 05:40

Additives in battery acid?

Guest - 13-6-2013 at 18:08

There have been two small bottles near it, one containing Potassium Hydroxide solution, the other containing Phosphoric Acid (I know acids and bases shouldn't be stored together but when they were put in their current home i didn't have much choice due to space limitations), both are sealed in screw top HDPE bottles, the phosphoric has some crystallisation around the outside of the bottle (no doubt from where i dribbled some while pouring years ago). Several feet away there is a bottle of copper solvent containing ammonia however it's also sealed in screw top HDPE bottles. I'll try to upload a pic. It's been a while since i've played around with chemistry and want to make sure it's not something that will give me a nasty surprise if i open it.

Guest - 13-6-2013 at 18:17

Picture

GEDC0193.JPG - 239kB

Endimion17 - 13-6-2013 at 23:59

I'm pretty much certain those crystals on bottles of acids are salts of ammonia. Ammonia is a normal constituent of our atmosphere, which concentration increases in areas of greater biological activity. After few years of sitting on a shelf, even relatively clean air will contribute to crystals or fogging near the bottle opening.
Those crystals are especially prominent, and appear rather quickly (months), in areas where bottles of ammonia or volatile ammonia compounds are stored, like most of the laboratories people usually encounter.
Of course, things will speed up if acids are stored in an old fashioned way, in old bottles with rather gritty ground glass joints that leak horribly. I remember working for few hours a week in one lab where tons of such bottles were sitting on shelves, few of them containing nitric acid and most of them containing aqueous metal salt solutions. There was always a decent smell of nitrous vapours lingering through the air. I'm sure the ppm levels were through the roof. Luckily for me, I got the hell out of there after few months.

phlogiston - 14-6-2013 at 03:40

Quote:
from where i dribbled some while pouring years ago). Several feet away there is a bottle of copper solvent containing ammonia however it's also sealed in screw top HDPE bottles. I'll try to upload a pic. It's been a while since i've played around with chemistry and


Ammonia vapour can slowly permeate through the HDPE. It could have accumulated over the years.

I always notice a smell around bottles of nitric acid, even professionally stored glass nitric acid bottles with an appropiate cap. If you touch any of the glass bottles surrounding it, your skin picks up a characteristic smell which is different from the nitric acid/nitric oxide itself.

Fantasma4500 - 14-6-2013 at 05:24

i have seen similar effect on 5 litre 62% HNO3 'bottles' or whatever you can call them..

apparently something from the air is capable of reacting with it..
the place i saw this was in a hardware store where they also had ammonia standing around (25%) but very well sealed off, so it couldnt have been that.. perhaps CO2 in air or something alike..?
there was literally needly crystals on the plastic, seemed like it had the same properties of aluminium nitrate
full plastic containers

annaandherdad - 14-6-2013 at 07:04

Quote: Originally posted by Pulverulescent  
Additives in battery acid?


This is discouraging. I had been hoping that the manufacturers of battery acid would have a motivation to sell pure acid, without additives or impurities. (Maybe some do.) This would be an advantage over drain cleaner as a source of OTC sulfuric acid, which often seems to have carbon and other impurities in it.

unionised - 14-6-2013 at 07:37

It's easy enough to check if it's ammonium sulphate.
Wipe it off and add a strong base like NaOH.
If the mixture smells of ammonia then you know it was an amonium salt.
It's also possible that it will smell a bit fishy due to traces of methylamines in air being trapped by the acid.