Quote Originally Posted by Jakebear View Post
Also noticed pH is up a bit to 7.7 from 7.5 before the Quat.
If everyone is seeing a pH rise when the chlorine gets used up by the "full" amount we have been seeing (the 3:2 molar ratio), then this gives an interesting clue as to what may be going on. The process of producing a combined chlorine, as with a chloramine or a chlorinated organic, is a basic (alkaline) process. In the case of ammonia, one of the hydrogen gets replaced with chlorine and produces water. Since the weak acid (HOCl) is thus consumed, this is a slightly basic process. In the case of creating a chlorinated organic, the process would be similar if this were a nitrogen with hydrogen attached, but PolyQuat has methyl groups attached to each nitrogen. So, a possible scenario is to replace the methyl group with chlorine thus releasing methanol. This is again a weakly basic (alkaline) process.

Achieving breakpoint is an acidic process that is so strong that the net of the above formation of a chlorinated compound plus breakpoint is a slightly acidic process. However, this is for the simple process of breaking ammonia. I am not clear as to what exactly would happen in breaking PolyQuat.

What doesn't make complete sense is that a replacement of one of the methyl groups, analagous to producing a monochloramine, would have the chlorine used up in a 1:1 molar ratio while if both methyl groups were replaced, analagous to producing a dichloramine, then the chlorine would get used up in a 2:1 molar ratio. Yet we are seeing a 3:2 molar ratio that is normally associated with achieving breakpoint of ammonia. Very strange indeed...

Richard