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BOD pH adjustment
Posted: Thursday, September 27, 2012 9:00 AM
Joined: 8/3/2012
Posts: 2

This may have been addressed before but we just recently bought SM 21st Edition and I was taking a look at the BOD method.


It says "Check pH; if it is not between 6.0 and 8.0 [adjust temperature], then adjust pH to 7.0 to 7.2..."


So, if I recieve a sample and the pH is 6.2 it's ok. But if the pH is 5.5 and I have to adjust it, then 6.8 is NOT ok. Really?? Can someone please explain this to me?


Couldn't they just leave it at "Neutralize sample to pH 6.5 to 7.5"?



Posted: Monday, October 29, 2012 11:22 AM
Joined: 10/12/2009
Posts: 11

The 18th edition says "adjust pH to 6.5 - 7.5" so somewhere between this and the 21st a change was made.


I am mystified as you.  I would have assumed that the final pH of 7.0 - 7.2 is to make sure the phosphate buffer is not overwhelmed by the use of a strong acid or base, but if that is so then why allow samples to be has high as 8.0 or as low as 6.0.