The authoritative public forum
  for Metal Finishing since 1989
-----

Di Water

2002

I have a DI Water Loop System at my plant. The system is 316 L. Our standard is pH 6.5 - 7 and conductivity is 1-10 microSiemens.

PROBLEM: Condition 1: I circulate the DI water at 40 degree C the pH = 7.1 and the conductivity = 3 Condition 2: I opened one user point => fill a 50 L vessel full with this DI Water (vessel is atmospheric)---> heated the vessel to 85 degree C(steam in the jacket)=> take out some sample => pH = 8.1 and conductivity = 5. This pH 8.1 is not accepted.

QUESTION: Could you advise me the correlation between pH to temperature and also between conductivity to temperature ?

Martuani Sterne Siregar
TetraPak - Jakarta, Indonesia

Both pH and conductivity vary considerably with temperature. Most standards specify that the temperature of the solution should be controlled at 25 °C for testing purposes. This allows for reproducible results at all times. Various tables are commercially available for conductivity and pH variations and can be usually got from companies that supply the testing equipment

Robert D Lilley
D.A.Q. Consulting - Singapore
2002