pH swings
- Thread starter awestruck
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THS
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"The ammonia molecule has a trigonal pyramidal shape with a bond angle of 107.8°, as predicted by the valence shell electron pair repulsion theory (VSEPR theory). The central nitrogen atom has five outer electrons with an additional electron from each hydrogen atom. This gives a total of eight electrons, or four electron pairs that are arranged tetrahedrally. Three of these electron pairs are used as bond pairs, which leaves one lone pair of electrons. The lone pair of electrons repel more strongly than bond pairs, therefore the bond angle is not 109.5°, as expected for a regular tetrahedral arrangement, but is measured at 107.8°. The nitrogen atom in the molecule has a lone electron pair, which makes ammonia a base, a proton acceptor. This shape gives the molecule a dipole moment and makes it polar. The molecule's polarity and, especially, its ability to form hydrogen bonds, makes ammonia highly miscible with water. Ammonia is moderately basic, a 1.0 M aqueous solution has a pH of 11.6 and if a strong acid is added to such a solution until the solution is neutral (pH = 7), 99.4% of the ammonia molecules are protonated. Temperature and salinity also affect the proportion of NH4+. The latter has the shape of a regular tetrahedron and is isoelectronic with methane. It is known to have the highest specific heat capacity of any substance"
Yes, ammonia can cause a pH shift
Yes, ammonia can cause a pH shift
I don't think the pH effect of ammonia will be measurable with our equipment at 0.25 ppm. It wouldn't cause the level to change continuously, if that's what you meant. It'd raise the pH a tiny amount. In reality, if there's ammonia, there's a decay process going on, and most of the decay byproducts tend to be acidic, so the pH likely would be lower than normal. That's very common in tanks that are cycling, for example.
awestruck
New member
Thank you for your responses. Here's why I'm asking: my friend's pH is swinging from 7.8 to 8.6 (night to day). Two things have changed for his system: 1) he changed salt brands, and 2) he moved to a new home. Prior to his move the pH was not swinging like it is now.
His alk. level stays consistent, he has good tank aeration, and he opens windows. He was showing .25 ppm of ammonia but not sure why.
The only thing I can think of is his house is very energy efficient and even with open windows it's just not exchanging gas to stabilize the pH. I've thought maybe a gas stove, central air, etc. I just don't know. We cannot seem to isolate anything that is causing this swing.
Any ideas?
His alk. level stays consistent, he has good tank aeration, and he opens windows. He was showing .25 ppm of ammonia but not sure why.
The only thing I can think of is his house is very energy efficient and even with open windows it's just not exchanging gas to stabilize the pH. I've thought maybe a gas stove, central air, etc. I just don't know. We cannot seem to isolate anything that is causing this swing.
Any ideas?
The ammonia might be due to measurement problem. I would get a second opinion on the kit, but dose some Prime or Amquel just in case.
That level of pH swing is normal for a house with the windows shut. Maybe his new home is more air-tight, as you suggest. People breathing can swing the pH that much, along with the normal swing associated with photosynthesis.
That level of pH swing is normal for a house with the windows shut. Maybe his new home is more air-tight, as you suggest. People breathing can swing the pH that much, along with the normal swing associated with photosynthesis.
I would wait until the ammonia issue has been resolved before worrying about the pH. Once that's resolved, we could look at issues with the pH measurement. If the measurements are accurate, then the problem must be carbon dioxide. There's simply nothing else that can change the pH.
I might check for films, likely oily buildups, on the water surface. They can interfere with aeration a lot. Also, if the tank has a skimmer, it might need a bit of cleaning. All in all, though, I think the problem likely is indoor carbon dioxide. For a few hundred dollars, I think you can get a meter to measure the level, but I don't think it's worth the investment.
I might check for films, likely oily buildups, on the water surface. They can interfere with aeration a lot. Also, if the tank has a skimmer, it might need a bit of cleaning. All in all, though, I think the problem likely is indoor carbon dioxide. For a few hundred dollars, I think you can get a meter to measure the level, but I don't think it's worth the investment.
