Sciencemadness Discussion Board

Has anyone ever had a bottle of pool grade calcium hypochlorite burst?

6dthjd1 - 29-5-2024 at 08:14

averageaussie - 29-5-2024 at 15:21

Not personally, but I have some ideas as to why it may have burst.
one reason may be the buildup of gasses in the container. hypochlorites are the salts of hypochlorous acid, HClO, and some of it may have been present. HClO reacts with HCl to form chlorine gas, which can slowly build up over time and cause a pressure increase, especially if not vented occasionally.
There are also probably dozens of reaction involving hypochlorites and hypochlorous acid that produce gasses which can build up over time (carbonate impurities might liberate CO2, etc, etc)
another, albeit probably wrong theory, is the formation of small amounts of nitrogen trichloride. hypochlorites can form monochloramine in the presence of ammonia (many nitrogen sources probably also work, such as urea), which can further react with many different nitrogen sources to produce small quantities of the explosive nitrogen trichloride. this may have slowly built up over time, until it violently decomposed to form nitrogen and chlorine gas, bursting the container. nitrogen trichloride is sensitive to light, so this would be the cause of our theoretical explosion.

Is all of this very silly and probably wrong? yes.
Do I care? no. Am I going to take this as a learning opportunity for myself inevitable getting corrected by anyone with common sense on this forum? also yes.
So please, correct me wherever I may have gotten something wrong, and propose actually realistic theories.
Have fun, keep learning.

bnull - 29-5-2024 at 15:40

One of the impurities of pool chlorine is calcium chloride, which is hygroscopic. It takes up water from the atmosphere, especially in rainy days. The whole mass gets wet, most of the time you won't notice that the powder is not as free flowing as it used to be in the beginning. Calcium hypochlorite keeps well when dry; when wet, it is a matter of time for it to decompose into calcium salts (chloride, chlorate, carbonate) and chlorine. Pressure builds up and one day the bottle bursts. Something similar happened to me, except that it was a small film canister and the problem with pressure was solved when I opened the canister and got a whiff of chlorine in my face.

@averageaussie: I suppose it burst as in "rupture". If it had burst into flames, I would be extremely interested in the exact conditions.

@6dthjd1: The bottle burst open, right?

pantone159 - 29-5-2024 at 17:05

I had a bottle of calcium hypochlorite fail. I don't really remember the details, but I did find that a bottle of this had failed, which explained some strange corrosion that I had noticed nearby, and then I disposed of it. Most likely the bottle cracked and broke open, but I forget exactly.

macckone - 30-5-2024 at 10:01

yes, it happens. if it is well sealed chlorine gets released and builds up.

6dthjd1 - 1-6-2024 at 09:53

Quote: Originally posted by bnull  
One of the impurities of pool chlorine is calcium chloride, which is hygroscopic. It takes up water from the atmosphere, especially in rainy days. The whole mass gets wet, most of the time you won't notice that the powder is not as free flowing as it used to be in the beginning. Calcium hypochlorite keeps well when dry; when wet, it is a matter of time for it to decompose into calcium salts (chloride, chlorate, carbonate) and chlorine. Pressure builds up and one day the bottle bursts. Something similar happened to me, except that it was a small film canister and the problem with pressure was solved when I opened the canister and got a whiff of chlorine in my face.

@averageaussie: I suppose it burst as in "rupture". If it had burst into flames, I would be extremely interested in the exact conditions.

@6dthjd1: The bottle burst open, right?


yes

woelen - 10-6-2024 at 03:50

My advice is not to buy calcium hypochlorite for long term storage. It slowly decomposes, regardless of how it is stored. My calcium hypochlorite still is free flowing and dry after years of storage, but every few weeks I have to unscrew the cap of the container, in which it is stored. Each time, there is quite some pressure inside the container, the gas being a mix of chlorine and oxygen.

TCCA and Na-DCCA have much better long-term storage properties and also are useful for making a chlorine generator.

Precipitates - 10-6-2024 at 17:41

I know not calcium hypochlorite per se but...when I opened my bleach bottle (6% sodium hypochlorite) yesterday it fixed slightly after only a few months, but storage is at room temperature. Here that is 30°C.

Chemateur80 - 12-6-2024 at 09:42

Quote: Originally posted by woelen  
My advice is not to buy calcium hypochlorite for long term storage. It slowly decomposes, regardless of how it is stored. My calcium hypochlorite still is free flowing and dry after years of storage, but every few weeks I have to unscrew the cap of the container, in which it is stored. Each time, there is quite some pressure inside the container, the gas being a mix of chlorine and oxygen.

TCCA and Na-DCCA have much better long-term storage properties and also are useful for making a chlorine generator.


I have a bottle of Na-DCCA that I used to make the copper complex. The bottle hadn't been opened for some years, so when I unscrewed the lid there was a popping sound and I was greeted with a lovely little cloud of chlorine.

I store my can of TCCA in a secondary container, and there's always a smell of chlorine when it's opened.

woelen - 12-6-2024 at 22:39

Yes, over the years, Na-DCCA and TCCA also can produce chlorine, or chloramines. But that is over a period of years. Hypochlorites do the same in weeks. If kept perfectly dry, then TCCA and Na-DCCA, however, can be kept for a very long time with only very little degradation.