FREE AVAILABLE CHLORINE ISN’T!

Why do the AFO text, the PPOA.org articles and the content of the PumpRoom Press always show quotation marks around the word free in the silly phrase “free” chlorine?  ‘Cause it’s never all free to work for us, that’s why.

You know that some percentage of near-useless OCl – (that hypochlorite ion) always exists along with the HOCl – the real thing – the associated hypochlorous acid that does the all-important oxidation and sanitation for us.  The ratio of HOCl to OCl- (missing that critical H+) varies rapidly according to changes in the water’s pH.

This “disassociation” business changes extremely as pH moves around.  The super-weak hypochlorite ion (OCl-) exists at about 25% of the free/available chlorine when the test-kit reading is at pH 7 while, at pH values approaching 8, the weak sister is dominant at roughly 75%. So FAC isn’t, ever, all “FAC” – it’s never all available. 

Whoever invented the FAC term knew more chemistry than he did the English language. While “free” in the term being discussed here means not combined (not ammonia products – remember smelly chloramine?), “available” remains pretty silly as the pH approaches 8.0, and not so hot even at typical pH values near 7.4.

An even more absurd term is CAC, combined available chlorine.  Virtually NONE of that chlorine compound is “available”.  In Dr. White’s famous Handbook of Chlorination, he states: “The term ‘available chlorine’ has no place in the field of water and waste treatment...”  He goes on to describe the archaic origins of the term.

So let’s quit using those silly terms FAC, TAC and CAC, and call ‘em what they are... “free”, “total” and “combined” chlorine.