Aging of Sodium Hypochlorite solution

[JohnDB]

One for the industrial chemists
I'm told that this stuff loses its effectiveness with time and other things. At supposedly 300 g/litre of sodium hypochlorite when fresh, the specific gravity is stated in the MSDS to be 1.15 to 1.20 @ 20 degC. If it loses effectiveness, does the SG reduce too? Just wondering if I weigh a litre of the stuff, and and based on that, how much I should dilute it to get a 5% solution for cleaning lichen off a steel roof. I bought 20 litres about 6 months ago, but there's nothing on the container to say when it was produced so it could be years old.

Other info from the MSDS:
Chemical Entity Proportion (%)
Water >60
Sodium Hypochlorite 10-30
Chlorine
SODIUM HYPOCHLORITE: Available chlorine, as chlorineTLV TWA: 0.5ppm, 1.5 mg/m3: STEL: 1 ppm,
2.9 mg/m3 ES Peak: 1 ppm, 3 mg/m3 CEL TWA: 2 mg/m3 (compare WEEL TWA) The odour threshold is
likely to be similar to that of chlorine, 0.3 ppm.

Thanks for any ideas!

 

[mikester]

The answer is "it depends". If it's in the original sealed container it will last longer than something re-sealed with poor gaskets. What it reduces to depends on your environmental conditions.

I wouldn't worry about it based on your application.

 

[Biker1mike]

Unopened and stored around room temperature it should be good for close to 2 years. Once opened it degrades quickly.
SPG will tell you very little.
300g/l is 30%. Dilute accordingly. 200ml to 1 liter is about 6 percent. close enough for cleaning

 

[DustyRusty]

If he uses it on the roof, will it kill the plants below when it washes off the roof?

 

[Biker1mike]

If he uses it on the roof, will it kill the plants below when it washes off the roof?

At 5% it will act just like household bleach.
plant and grass kill will depend on how much water is used to rinse and contact time.

 

[Dave Ogren]

That is the best stuff to open up drain lines.
Here it is only sold by plumbing supply houses so not available in the retail market, so very few know about it. If you use about 6 pounds a year it will keep your septic tank and rain lines in good shape longer.
Dave

 

[JohnDB]

Thanks for your replies everyone. It's in the original container, cap has good seals, so I'll assume still full or near full strength.

I have used it previously similarly diluted for washing down walls pre-painting, lots of rinsing with fresh water, grass was unaffected.

 

[hagrid]

That is the best stuff to open up drain lines.
Here it is only sold by plumbing supply houses so not available in the retail market, so very few know about it. If you use about 6 pounds a year it will keep your septic tank and rain lines in good shape longer.
Dave

Hypochlorite or hydroxide?

 

[Dave Ogren]

Hypochlorite or hydroxide?

You are right, I screwed up guess I can't read. I meant sodium hydroxide. Thanks.
Dave