pixelpixi
Guest
For a while I've been thinking that my pH is chronically low. Since I have two separate ph probes that I've been testing with, though, I ruled out calibration as a problem early on. Since then I've been dripping kalkwasser, doing outside air airation tests, double checking alk, and scratching my head all in an attempt to understand why my ph is below normal.
Then I thought more about the calibration of my ph probes. I calibrated them both at the same time, so if the calibration solution was contaminated that could be my problem. Thinking more about it and doing some tests with fresh calibration solution, I've determined that that's exactly it.
My ph probes are both in the tank most all the time. One is normally in the effluent cup of my calcium reactor and the other up in a corner of my display tank. I think what happened is that some amount of calcium carbonate precipitated on the probes. I didn't get them completely clean before calibrating so some of the calcium carbonate dissolved and raised the ph of the calibration solutions. In fact, thinking back I now remember that it took an unusually long time for the calibration to "settle down." I thought that the probe might be just getting a little old and was slow to respond, but it was probably the calcium carbonate dissolving.
So, I soaked both probes in vinegar, rinsed them well, and then recalibrated. I think they're much more accurate now, though I did run into one other issue. With the second probe I calibrated, the ph seemed to continue to drop for a fairly long time while in the calibration solution. Checking the solution with the first probe, it appears that the ph really was dropping. I think this might be due to some acid from the vinegar leaching into the plastic of the probe and then leaching back out into the calibration solution.
So the things I've learned...
1) make sure probes are completely clean and free of deposits before calibrating
2) if a probe seems to take a long time (minutes instead of seconds) to adjust, the probe may be affecting the solution
Any thoughts on this stuff from you chemistry experts? Do my conclusions seem correct?
Also, any thoughts on what I could do to avoid the vinegar leaching problem?
Then I thought more about the calibration of my ph probes. I calibrated them both at the same time, so if the calibration solution was contaminated that could be my problem. Thinking more about it and doing some tests with fresh calibration solution, I've determined that that's exactly it.
My ph probes are both in the tank most all the time. One is normally in the effluent cup of my calcium reactor and the other up in a corner of my display tank. I think what happened is that some amount of calcium carbonate precipitated on the probes. I didn't get them completely clean before calibrating so some of the calcium carbonate dissolved and raised the ph of the calibration solutions. In fact, thinking back I now remember that it took an unusually long time for the calibration to "settle down." I thought that the probe might be just getting a little old and was slow to respond, but it was probably the calcium carbonate dissolving.
So, I soaked both probes in vinegar, rinsed them well, and then recalibrated. I think they're much more accurate now, though I did run into one other issue. With the second probe I calibrated, the ph seemed to continue to drop for a fairly long time while in the calibration solution. Checking the solution with the first probe, it appears that the ph really was dropping. I think this might be due to some acid from the vinegar leaching into the plastic of the probe and then leaching back out into the calibration solution.
So the things I've learned...
1) make sure probes are completely clean and free of deposits before calibrating
2) if a probe seems to take a long time (minutes instead of seconds) to adjust, the probe may be affecting the solution
Any thoughts on this stuff from you chemistry experts? Do my conclusions seem correct?
Also, any thoughts on what I could do to avoid the vinegar leaching problem?
