coast2coast
Active Member
I saw this online and wanted everyones input...
1. The pH of totally pure water is around 7 (with the exact value depending on temperature). As carbon dioxide from the atmosphere enters the water, the pH drops into the 6’s and even into the 5’s, depending on the amount of CO[SIZE=-1]2[/SIZE]. At saturation with the level of CO[SIZE=-1]2[/SIZE] in normal (outside) air, the pH would be about 5.66. Indoor air often has even more CO[SIZE=-1]2[/SIZE], and the pH can drop a bit lower, into the 5’s. Consequently, the pH of highly purified water coming from an RO/DI unit is expected to be in the pH 5-7 range.
2. The pH of highly purified water is not accurately measured by test kits, or by pH meters. There are several different reasons for this, including the fact that highly purified water has very little buffering capacity, so its pH is easily changed. Even the acidity or basicity of a pH test kit’s indicator dye is enough to alter pure water’s measured pH. As for pH meters, the probes themselves do not function very well in the very low ionic strength of pure freshwater, and trace impurities on them can swing the pH around quite a bit.
3. The pH of the combination of two solutions does not necessarily reflect the average (not even a weighted average) of their two pH values. The final pH of a mixture may actually not even be between the pH’s of the two solutions when combined. Consequently, adding pH 7 pure water to pH 8.2 seawater may not even result in a pH below 8.2, but rather might be higher than 8.2
basically I use a RO/DI system and im concerned about the accurate measurement of my pH
1. The pH of totally pure water is around 7 (with the exact value depending on temperature). As carbon dioxide from the atmosphere enters the water, the pH drops into the 6’s and even into the 5’s, depending on the amount of CO[SIZE=-1]2[/SIZE]. At saturation with the level of CO[SIZE=-1]2[/SIZE] in normal (outside) air, the pH would be about 5.66. Indoor air often has even more CO[SIZE=-1]2[/SIZE], and the pH can drop a bit lower, into the 5’s. Consequently, the pH of highly purified water coming from an RO/DI unit is expected to be in the pH 5-7 range.
2. The pH of highly purified water is not accurately measured by test kits, or by pH meters. There are several different reasons for this, including the fact that highly purified water has very little buffering capacity, so its pH is easily changed. Even the acidity or basicity of a pH test kit’s indicator dye is enough to alter pure water’s measured pH. As for pH meters, the probes themselves do not function very well in the very low ionic strength of pure freshwater, and trace impurities on them can swing the pH around quite a bit.
3. The pH of the combination of two solutions does not necessarily reflect the average (not even a weighted average) of their two pH values. The final pH of a mixture may actually not even be between the pH’s of the two solutions when combined. Consequently, adding pH 7 pure water to pH 8.2 seawater may not even result in a pH below 8.2, but rather might be higher than 8.2
basically I use a RO/DI system and im concerned about the accurate measurement of my pH
