Hanna Instruments HI 2212 Instruction Manual

Contents

Hanna Instruments HI 2212 Instruction Manual Manual pdf 28 page image

28Typical Electrode LifeAmbient Temperature 1 – 3 years90 ºC Less than 4 months120 ºC Less than 1 monthAlkaline ErrorHigh concentrations of sodium ions interfere with readings in alkalinesolutions. The pH at which the interference starts to be significantdepends upon the composition of the glass. This interference is calledalkaline error and causes the pH to be underestimated. Hanna’s glassformulations have the indicated characteristics.The resistance of glass electrodes partially depends on the temperature.The lower the temperature, the higher the resistance. It takes more timefor the reading to stabilize if the resistance is higher. In addition, theresponse time will suffer to a greater degree at temperatures below 25 ºC.Since the resistance of the pH electrode is in the range of 50 – 200Mohm, the current across the membrane is in the pico Ampere range.Large currents can disturb the calibration of the electrode for many hours.For these reasons high humidity environments, short circuits and staticdischarges are detrimental to a stable pH reading.The pH electrode’s life also depends on the temperature. If constantlyused at high temperatures, the electrode life is drastically reduced.1.0 Mol L-1 Na+0.1 Mol L-1 Na+Sodium Ion Correction for the Glass at 20-25 ºC13.0013.5014.0012.5013.0013.5014.000.100.140.200.100.180.29TEMPERATURE CORRELATIONTEMPERATURE CORRELATIONTEMPERATURE CORRELATIONTEMPERATURE CORRELATIONTEMPERATURE CORRELATIONFORFORFORFORFOR ppppp H SENSITIVE GLASSH SENSITIVE GLASSH SENSITIVE GLASSH SENSITIVE GLASSH SENSITIVE GLASS