Breakpoint Chlorination

[chem geek]

Yet another update in this continuing saga. This thread seems to indicate that perhaps the "ppm Chlorine" definition is based on the Chlorine gas (Cl2) equivalent where chlorine gas is 100%. I know that this is what is used for what is termed "available chlorine" when comparing different chlorine sources, but I did not know if that is what is also used for measuring chlorine from the test kits. This seems doubful and strange, but this wouldn't be the first time an unusual convention is used in the pool industry. I'll keep y'all posted. [EDIT] So far, most every source I can find says that ppm chlorine has the "part" in part per million be the weight of chlorine and the context has always been HOCl + OCl- (CYA is not talked about so Cl-CYA is included as if it were HOCl/OCl-). [END-EDIT]

[SECOND-EDIT] I found the answer! It's at this website where it says "Although Cl2 does not exist in potable waters, for historical reasons FAC, CAC and total chlorine are still expressed as mg/L as Cl2" so I need to correct my spreadsheet. This will somewhat effect all of my graphs, tables, etc. calculating ppm HOCl from FC (the FC numbers will go up by 35% holding everything else constant). The points and principles won't change, but some of the specific numbers will. I'm sure Michael will be very relieved to know that the proper adjustment to his algorithm in his program is quite minor and can possibly be ignored. [END-SECOND-EDIT]

Richard