Clorox Regular

[Pool in Carolina Blue]

I bought some jugs at Costco recently that are labeled as 6%. However, there is a note that says that it will yield 5.7% available chlorine. Anyone know why the yield is diminished?

[chem geek]

The 6% refers to the Weight % of Sodium Hypochlorite. The % Available Chlorine is the equivalent weight % of chlorine gas which is the standard (defined as 100%) used for all chlorine measurements, including Free Chlorine (FC) level. The molecular weight of Sodium Hypochlorite (NaOCl) is 74.4422 while the molecular weight of chlorine gas (Cl2) is 70.906 so the formula is:

Weight % Available Chlorine = Weight % Sodium Hypochlorite * (70.906 / 74.4422)

Since 74.4422/70.906 = 1.050 it's easier to remember to just divide the weight % by 1.05 to get % available chlorine. 6% / 1.05 = 5.7%

So Clorox did not lower their chlorine level when they simply added the clarification that their 6% bleach yielded 5.7% available chlorine.

To make matters even more confusing, there is another quantity called "Trade %" which is often used to measure chlorinating liquid. The Trade % is the volume % of available chlorine so this is related to the weight % of available chlorine by the density (specific gravity) of the liquid as follows:

Trade % = Weight % Available Chlorine * Specific Gravity

The density of clorox regular bleach is about 1.1 so the Trade % is 5.7% * 1.1 = 6.3%. It is this trade % that is most accurately used for BleachCalc since it is the % of available chlorine (in similar units as FC) per volume of liquid. So, 1 gallon of 6.3% (trade) bleach would give 6.3 ppm FC in 10,000 gallons of water. The density of 12.5% chlorinating liquid is around 1.16 due to the higher dissolved chlorine and the extra "dense" base (sodium hydroxide) that is added.

Richard

[Pool in Carolina Blue]

Thanks Richard.

[Simmons99]

The 6% refers to the Weight % of Sodium Hypochlorite. The % Available Chlorine is the equivalent weight % of chlorine gas which is the standard (defined as 100%) used for all chlorine measurements, including Free Chlorine (FC) level. The molecular weight of Sodium Hypochlorite (NaOCl) is 74.4422 while the molecular weight of chlorine gas (Cl2) is 70.906 so the formula is:

Weight % Available Chlorine = Weight % Sodium Hypochlorite * (70.906 / 74.4422)

Since 74.4422/70.906 = 1.050 it's easier to remember to just divide the weight % by 1.05 to get % available chlorine. 6% / 1.05 = 5.7%

So Clorox did not lower their chlorine level when they simply added the clarification that their 6% bleach yielded 5.7% available chlorine.

To make matters even more confusing, there is another quantity called "Trade %" which is often used to measure chlorinating liquid. The Trade % is the volume % of available chlorine so this is related to the weight % of available chlorine by the density (specific gravity) of the liquid as follows:

Trade % = Weight % Available Chlorine * Specific Gravity

The density of clorox regular bleach is about 1.1 so the Trade % is 5.7% * 1.1 = 6.3%. It is this trade % that is most accurately used for BleachCalc since it is the % of available chlorine (in similar units as FC) per volume of liquid. So, 1 gallon of 6.3% (trade) bleach would give 6.3 ppm FC in 10,000 gallons of water. The density of 12.5% chlorinating liquid is around 1.16 due to the higher dissolved chlorine and the extra "dense" base (sodium hydroxide) that is added.

Richard

....... uh you totally got me on this one . So you use 6.3% in bleach calc - but no normal human would be able to deduce that was the *actual* percentage of chlorine. So glad I use a SWCG

[chem geek]

....... uh you totally got me on this one . So you use 6.3% in bleach calc - but no normal human would be able to deduce that was the *actual* percentage of chlorine. So glad I use a SWCG

Well, given the uncertainties of measurements (including pool volume, test kit accuracy, etc.) it doesn't really matter whether you used 5.7%, 6% or 6.3% in BleachCalc since you are going to end up with reasonably close-to-target amounts of chlorine for any of these. The error between 5.7% and 6.3% is only 10% and I don't think anyone is trying to target their FC levels to be that accurate so even though I present the technically accurate information, you can ignore such dribble for practical purposes.

Richard

[fcfrey]

Richard,

LOL --- Your dribble represents a very important lesson in chemistry that most people are learning ---- they just don't know it yet

Keep it coming, I, for one, read every one of your posts & since I have found myself saying, "Richard had an interesting tidbit about that" or " I saw a chart that Richard made --- somewhere" ----I now print most for further review.

[Simmons99]

Richard,

Don't get me wrong - I LOVE your posts - they are so full of logic (which I like). Sometimes my brain cannot process it all - and this post I was actually laughing - because it is SO you