[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

Re: Alkalinity and Phosphates

On Friday 10 January 2003 04:45, James wrote:

> But Greger's example notwithstanding, from the number of books on water
> chemistry which I have so far consulted, and the cursory reference to
> "other sources of Alkalinity", I'd venture to guess that such contamination
> of natural water, especially any water considered fit for human
> consumption, has got to be very rare, and the water which comes out of most
> people's tap follows the Alkalinity = KH rule far more often than when it
> doesn't. And thus, its not something that most of us have to worry about.
> Am I making too many assumptions here?

I think the alkalinity titration is the only standard method for bicarbonate 
analysis.  In fresh natural water or in tap water there is rarely any reason 
to suspect that the results aren't spot on.   A few years ago I reviewed a 
large body of data from streams and wetlands in the US and found that 
blackwater swamps, mostly in the southeast US were the only waters in which I 
suspected the alkalinity tests weren't good bicarbonate results.  Heavily 
polluted waters (e.g., landfill leachates) are the only other case I know of 
where the interference with the alkalinity titration produces incorrect 
bicarbonate results.

Even in aquaria the incidence of problems is probably fairly low with 
significant effects limited to cases where the measured KH is pretty low.

> Roger mentioned an "organic soup" - (i.e. aquarium water) and I can see how
> that might begin to show some of these influences. How practical would it
> be to measure the Alkalinity of tapwater and compare that figure to the
> Alkalinity of the water in the aquarium? Would the difference indicate
> anything?

That might help, but there are many complicating problems.  Evaporation from 
the aquarium will cause KH to increase, various water treatments will cause KH
to increase, dissolution of shells in the substrate or snail shells after the 
death of the snail will cause KH to increase, nitrification causes KH to 
decrease, growing snails causes KH to decrease, CO2 production by 
electrolysis causes KH to decrease, and the KH in many water supplies varies 
up and down quite a bit.  All-in-all I wouldn't expect the comparison to be 
very useful.

Roger Miller