Chlorine Bleach

[Mullardman]

Er Indoors is watching one of those Groundhog Day telly progs featuring one of those household cleaning 'experts'. She has a lot of good ideas but she also made what I believe to be a totally inaccurate statement saying that 'chlorine bleach is terrible, not water soluble and hangs around for ages'

Now my 1965 'O' Level Chemistry is a little rusty, but if I'm not mistaken, chlorine bleach is hypochlorous acid, which gives up oxygen and maybe chlorine and essentially degrades to sodium chloride, aka common salt.
What's more, its antibacterial effects derive from rapid oxidation, which gives bacteria no chance to mutate, unlike so called 'antibacterials'.
Any of our resident chemists care to comment?

 

[Seeker_UK]

Not quite - household bleach is a solution of sodium hypochlorite, which is the sodium salt of hypochlorous acid.

But yes, it's soluble in water and can be decomposed into NaCl and oxygen.

 

[Darth Vader]

Maybe there was confusion and the presenter was referring to bleaching powder that does contain some calcium hydroxide (slaked lime) and as we know is not very soluble - remember lime water?

I was around 6 or 7 when I had my Chemistry set and remember making 'Milton' by passing 3V from a battery via carbon (graphite) rods into a solution made from tap water and table salt and moving the rods around to mix the chlorine into the alkaline solution to make sodium hypochlorite.

DV

 

[Vinny]

The liquid bleach that you buy in any supermarket is a solution of sodium hypochlorite, which is an unstable white powder, freely soluble in water. The problem is that it has no real shelf-life, so it is stabilised with caustic soda (sodium hydroxide), which is why what is called bleach, is actually alkaline and feels slightly soapy if you rub a drop between two fingers.
Actual bleach is acidic as it decomposes to generate chlorine - which is what you smell, and does the disinfection, and bleaching.

Any residue, apart from thickeners if it is thick bleach, will be a mix of salt (sodium chloride) and sodium carbonate, from reaction with atmospheric carbon dioxide. Any thickener is highly likely to be a cellulose ester - like wallpaper paste.

So far as I am aware, what is commonly called dairy hyprochlorite has no stabilising caustic in it.

Where any calcium might come from, as suggested above, I have no idea.

 

[NigelP]

Agree with my learned colleagues solid bleach powder is “calcium hypochlorite” and liquid bleach sodium hypochlorite as said hypochlorites are unstable and the sodium hypochlorite we used in the lab was 13-15% and you had to titrate to get actual strength accurately. Yes if you acidify you get chlorine given off and the liquid and all products are fully water soluble.

 

[Vinny]

Which is what NigelP said.

Apologies - why don't I read things properly?

I have not seen bleaching powder - Ajax, Vim etc., for many a year though.

 

[stevec67]

As others correctly point out household bleach, used in the food industry, is sodium hypochlorite stabilised with sodium hydroxide. It is NaHClO3, if there is not an excess of hydroxide (NaOH) then it decomposes to NaCl (common salt), oxygen (that does the bleaching as others say) and water.

 

[Mullardman]

So in short and in principle I was right?

 

[stevec67]

Er Indoors is watching one of those Groundhog Day telly progs featuring one of those household cleaning 'experts'. She has a lot of good ideas but she also made what I believe to be a totally inaccurate statement saying that 'chlorine bleach is terrible

It's pretty unpleasant but it works.

, not water soluble

Incorrect.

and hangs around for ages'

So what if it does? Actually it doesn't because it's really reactive and burns everything it hits.

Now my 1965 'O' Level Chemistry is a little rusty, but if I'm not mistaken, chlorine bleach is hypochlorous acid,

More likely to be sodium hypochlorite becaise of the excess of NaOH. It's NaHClO3, hypochlorous acid would be H2ClO3 and I doubt that this is stable.

which gives up oxygen and maybe chlorine and essentially degrades to sodium chloride, aka common salt.

Seems fair. I worked it out the other day for work.
2x NaHClO3 >>> 2x NaOH, 1x Cl2, 2x O2
This is why you have to add NaOH to keep it as NaHClO3, if you add acid it reacts with the NaOH and the stuff degrades, releasing chlorine gas.

What's more, its antibacterial effects derive from rapid oxidation,

Correct

which gives bacteria no chance to mutate,

correct

unlike so called 'antibacterials'.

Depends on how they work. Things like QACs do it via detergency so likewise, no resistance

Any of our resident chemists care to comment?

Aye

So in short and in principle I was right?

Doesn't look far off the truth.

 

[Vinny]

So in short and in principle I was right?

Yes, details may vary, but correct.

The chemistry is fantastically more complicated; anyone curious see the Wiki page.

 

[stevec67]

The chemistry is fantastically more complicated; anyone curious see the Wiki page.

Yes it does go all over the place depending on pH etc.

 

[Yank]

Apologies - why don't I read things properly?

I have not seen bleaching powder - Ajax, Vim etc., for many a year though.

We still have Ajax and Comet easily available over here. I keep a can of Comet for cleaning the terlet.

 

[stevec67]

We still have Ajax and Comet easily available over here. I keep a can of Comet for cleaning the terlet.

Seems to have gone out of fashion in the UK. Liquid sprays are more the thing here.