PN C04540-01-1990 Water and waste water Tests for pH, acidity and alkalinity Electrometric pH determination of water and waste water with specific conductivity 10 nS/cm and higher
1990PN C04540-01-1990 Water and waste water Tests for pH, acidity and alkalinity Electrometric pH determination of water and waste water with specific conductivity 10 nS/cm and higher