We've been batting some ideas and questions around on this thread.
Some of us thought it would be better to continue on it's own thread.
Any and all questions, comments on water quality, cycling, treatment, filtering, chemicals.....etc.
pH, Carbon Dioxide (CO2) and Alkalinity
The pH of water is an index of hydrogen ion (H+) activity of water. The pH scale
(range from 0 to 14) is logarithmic (base 10), an important fact to remember because a dropof 1 pH unit indicates a 10 fold increase in hydrogen ions (H+) present in water. A pH value may fall anywhere on a scale from 0 (strongly acidic) to 14 (strongly basic or alkaline), with a value of 7 representing neutrality (= 10-7 moles/liter of H+ ions).
The pH of most productive natural waters that are unaffected by pollution is normally in therange of 6.5 to 8.5 at sunrise, typically closer to 7 than 8. Diurnal variation is related to photosynthesis:
(1) CO2 + H2O <-------> C6H12O6 + O2
The controlling factor for pH in most aquacultural is the relationship between algal photosynthesis, carbon dioxide (CO2), and the bicarbonate (HC03-+H) buffering system:
(2) CO2 + H2O <-------> H2C03 <--------> HC03- + H+
At night, respiration by bacteria, plants, and animals results in oxygen consumption and carbon dioxide production, the reaction in formula (2) goes from left to right, first producing carbonic acid (H2C03), then bicarbonate HC03- and H+ ions; the increase in H+ causes the pH to drop. During sunlight, respiration continues, but algae use CO2 for photosynthesis, formula (1); the reaction of formula (1) goes from right to left, reducing the abundance of H+ ions, and pH goes up. In productive ponds, especially those with low alkalinity, the daytime pH may reach 10, which can be lethal to young fish. Toxicity of other compounds to fish, especially ammonia and chlorine, are affected by pH
So that swapping back and forth of the H+ ion between carbonic acid and bicarbonate is where the H+ comes form that ionizes ammonia into ammonium?
Prime adds lots of H+ Is that it? I'm missing something. Why doesn't this pH go down when you add Prime?
ammonia/ammonium ratio is primarily a function of pH, Prime, apparently does not affect or is not affected by pH, so the manner in which Prime neutralizes ammonia must be other than a simple ammonia to ammonium conversion
[quote=Hallyx;3168617]So that swapping back and forth of the H+ ion between carbonic acid and bicarbonate is where the H+ comes form that ionizes ammonia into ammonium?
Prime adds lots of H+ Is that it? I'm missing something. Why doesn't this pH go down when you add Prime?[/quote]
I have heard that pH does in fact go down when adding prime.
I have only used prime once in an extreme case in a marine tank and the ph went from 8.4-8.8 (api high range test kit) to around 7.8 or lower.
I have also seen posts on these forums that kH crashes also.
still that's just my .02
Seachem Priime is a reducing agent technically a complexed hydrosulfite salt (Sodium formaldehydebisulfite CH4O4S ) Sodium Hydrosulfite is a very strong reducing agent. A reducing agent is the opposite of an oxidant as it will reduce and or remove any oxidant such as chlorine, ozone, chlorine dioxide, just to name a few it will also remove oxygen. Other products, such as hydroxymethanesulfonate (HOCH2SO3-; a known ammonia binder can be used to treat chloraminated water because they both break down chloramine and bind up the ammonia.
The reaction of ammonia with hydroxymethanesulfonate is mechanistically complicated, possibly involving decomposition to formaldehyde and reformation to the product (aminomethanesulfonate). The simplified overall reaction is believed to be:
NH3 + HOCH2SO3- -------> H2NCH2SO3- + H2O
What ultimately happens to the aminomethanesulfonate in the aquarium is not well established Even more complicated is the reaction of hydroxymethanesulfonate with chloramine, or chlorine (as Cl2 or HOCl). In this case, the products that are formed have not been established.
, Sodium Hydrosulfite performs one of the following three roles:
1. As a reducing agent, hydrosulfite chemically reduces other components by donating an electron or electrons.
2. As a sulfonating agent, hydrosulfite adds sulfur to another chemical compound.
3. As a cation source, hydrosulfite adds a cation, or sodium, to a product system increasing the conductivity and TDS
I really a much more complex reaction that people realize.
It appears it is a great deal more complicated than Seachem's explanation of how Prime works. I wonder if they dumbed it down for us silly keepers, or if they really know what's going on. They say they're not sure how Prime handles nitrite.
Thanks for that explanation, Rick. I'm sure I'll understand it better if I reread it a few times.
Perhaps it is a secondary effect. Not directly caused by the direct chemical reactions.
In my case above there was a huge ammonia spike caused by my inadvertant addition of a toxin. The pH crash occurred about a week or two after treating with Prime and could have been part of the recycling as the tank recovered.
thanks for reply.
and my .02
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