How to test for accurate PO4

[Aqua-Digital]

I have been asked many times why it is recommended to do heat tests when testing for po4.

Well first here is how it is done

take a sample of water to be tested and then heat to 80 degrees C now do your PO4 test and take the reading. Then allow a fresh un tested sample of the heated water to cool and test again, take reading.

Why do this.

When you heat the water the binding of PO4 from the water is removed and can be tested far more accurately, when normal tests are done, much of the PO4 (up to 3-4 times the amount) remains untested.

Try it and see

[Delphinus]

How long do you keep the sample at 80C? Or is simply heating it to 80C sufficient and you can start letting it cool immediately?

How best to acheive heating a sample to 80C? Microwave? Water bath in a pot on the stove?

Why take two readings (one of the heated sample and one of the recooled sample)? What does it mean if you get differing values, which one is the more correct?

[Aqua-Digital]

Heat to 80 degrees then remove from heat allow to cool for a minute and then test

Any method of heating but dont boil it and then cool it, so has to be controlled heating.