Clorox Regular

[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