Alkalinity and Phosphates

["James Purchase" <jppurchase at rogers_com>]

Cavan asked a question the other day about the possible effect Phosphates
have on Alkalinity readings. In one form or another, this question has been
battered around online since at least 1994. I've NEVER seen anyone step up
to the bat to volunteer an answer. Lots of stuff which says that things like
Borates, Phosphates and Sulphates CAN add to Alkalinity readings, but
nothing which says by how much, or to what degree.

Is there ANY way to separate out the possible interference from Phosphates,
Borates and/or Sulphates to an Alkalinity reading? The "standard test"
doesn't seem to be able to distinguish what bases are present, it just
assumes (and reports) things in terms of CaCO3 (assuming, or at least
reporting, that all of the Alkalinity is due to OH-HCO3-CO3). Can you take
the concentration of either Phosphates and/or Sulphates (both of which are
testable parameters) and, via some mathematical sleight of hand, calculate
the contribution of these species to Alkalinity?

I've found some web based reference material from the U.S. Dept. of Energy
which leads me to believe that it IS possible. They have tables with
conversion factors designed to be used in boilers when TSP is added to
increase Alklainity. So _somebody_ has figured this stuff out.

James Purchase
Toronto