OT cillit bang crystals vacuum creation

[mike ring]

Sorry the subject lines a bit cryptic, but I'd like the brains truss to tell me what's going on here.

My plastic water bottle, which is refilled regularly with tap water, was suffering a bit od green algae, so I put some of the above crystals in, and a bout 1/3 filled with hot tap water, put the cap on and gavre it a shake, and it foamed up like Andrews.

I expected a pressure buildup, and was ready to ease the cap, but the opposite happened, and the bottle was squashed nearly flat by air pressure, and developed a permanent dimple in the bottom, so some serious vacuum was being formed.

But how? - it's alleged to have 15-30% oxygen based bleaching agent, and

[Chipmunk]

[snippage]

I am not certain of the chemistry these type of compounds used, but is it at all possible that the air is being reduced in volume by 20%? That would tend to indicate that the cleaner as well as supplying its own oxygen is somehow catalyzing a reaction using the oxygen in the air too.

I can't find any reference to any reaction that would cause that, as the chemical involved is sodium percarbonate which should *produce* oxygen as you said, rather than taking it up. But it's possible it's starting a reaction which then consumes all the oxygen including that which was there to begin with.

My chemistry's a little rusty due to 10 years lack of use :-)

[Frank Erskine]

I'm not too sure about the variations of Cillit Bang, but I have a bottle of CB Universal Degreaser, which despite it's silly name does seem to work (on the inch-thick-of-grease leccy hob) . However, there is a caveat on this particular variation that it isn't suitable for direct food contact surfaces, which I assume to include the insides of water bottles.

Perhaps the crystalline stuff IS suitable for food-contact surfaces, but it is worth checking out.

Regarding the contraction effect, I'm no chemist (it's the subject I failed at O level!), but perhaps the hot water was cooled quickly by the CB thereby producing a partial vacuum. Have you tried reinstating the plastic bottle by pouring in hot water and leaving the cap off until the water cools?

[mike ring]

Chipmunk wrote in news: [e-mail]:

Mine too, but I think the effect is much more dramatic than the removal of just oxygen could do; that shaould only drop the pressure by 20% or so.

This looked like a pretty hard vacuum, I couldn't squash it any flatter, and it felt rock hard. The bottle was only about 1/3 full so a lot of air had disappeared!

mike

[mike ring]

mike ring wrote in

I just tried it with cillit bang squirt, and just got a bit of overpressure on shaking, due to heatig the air

[Chipmunk]

Is it possible that the oxygen is displacing the air, thus leaving the entire 'air' space in the bottle containing only oxygen? This would then react with things causing the vacuum, that's about all I can think of, other than the possibility of the lid acting as a 1 way valve of some kind.

[Richard]

FWIW I clean water bottles and Thermos flasks with denture cleaning tablets.

Richard (with own teeth - still)