duganderson
Member
I'm currently using about 23 ml daily of baking soda solution mixed at the BRS ratio for Sodium Bicarbonate (1 cup and 4 T. baking soda per gallon) to maintain my Alk at about 10.0
I just read this post that makes me nervous about using sodium bicarbonate due to the potential of a big PH drop. Please see this post below and give me your thoughts if I should change to sodium carbonate instead for my daily dosing. By the way, I dose in the morning after my lights have been off for about 6-8 hours. I'm guessing I should switch my dosing time to evening when my lights have been on for several hours and the PH is highest....right?
Here is the post.......(please see the text in red that I am referring to)
"Several things to consider here.
Sodium bicarbonate is highly soluble. 1 gm of Sodium Bicarbonate dissolves in 10 ml (2 tsp) of room temperature water. The resulting solution of sodium bicarbonate predominately dissociates into sodium and a bicarbonate ions. The bicarbonate only slightly changes (a small amount) via hydrolysis by water to form carbonic acid and a hydroxyl ion. The resulting solution is only slightly alkaline, a pH of around 8.2.
The resulting hydrolysis and resulting pH can be affected by other ions in solution. One of the problems of using sodium bicarbonate over time is that it changes the composition of the conservative elements in seawater. Its use demands that we do regular water changes to avoid depletion and ratio changes of the essential conservative elements in seawater mixes on a frequent regular basis. Craig Bingman has a study using a computer model where many of the conservative elements change their quantities in seawater due to dilutional effect and consumption and elimination. If borate is one, then the buffer capacity of seawater is further diminished, leaving mostly bicarbonate and carbonate to handle the acid/base reactions.
the baking soda was doing what it was supposed to do. At best, this solution will dissociate further to form the carbonate ion, which in association with sodium will form a very basic solution (Na CARBONATE dissociates in water to a pH of 11.6, very basic). As the dissociation of bicarbonate to carbonate is very small, this is of little significance if there are a large amount of organic acids in the water column, as the bicarbonate (predominant specie in this reaction) will be consumed by the acids, driving carbonate back to the reactant bicarbonate and further dropping pH.
So what do these things mean to us? When adding sodium BICARBONATE to the system, if there were no other ions, the pH would only be 8.2, not a lot to affect a pH of 8.1 much to start with. If there are significant amounts of organic acids in the water column, they will quickly react with the bicarbonate ion to form the neutral form of that acid and release carbon dioxide gas into the water column. This results in a rapid drop of the pH of the water column due to the formation of carbonic acid and a depletion of the buffer capacity of the solution, not what we might expect when adding baking soda. However, in the presence of adequate amounts of calcium, and the presence of carbonate ions, the pH would be maintained, and bicarbonate is conserved rather than consumed to maintain alkalinity/buffer of the water column. This is why most reef buffer builders contain 8 parts sodium bicarbonate and 1 part sodium carbonate The high pH of the carbonate helps offset the resulting release of carbon dioxide which leads to the formation of carbonic acid in seawater reactions. Sodium Bicarbonate by itself is so slightly alkaline that it fails to turn phenolphthalein indicator red. Sodium Carbonate, on the other hand, turns phenolphthalein dark red due to it's extensive ionization in water. In addition, the carbonate is now available to replenish the bicarbonate ion in the water column, further conserving alkalinity of our seawater."
I just read this post that makes me nervous about using sodium bicarbonate due to the potential of a big PH drop. Please see this post below and give me your thoughts if I should change to sodium carbonate instead for my daily dosing. By the way, I dose in the morning after my lights have been off for about 6-8 hours. I'm guessing I should switch my dosing time to evening when my lights have been on for several hours and the PH is highest....right?
Here is the post.......(please see the text in red that I am referring to)
"Several things to consider here.
Sodium bicarbonate is highly soluble. 1 gm of Sodium Bicarbonate dissolves in 10 ml (2 tsp) of room temperature water. The resulting solution of sodium bicarbonate predominately dissociates into sodium and a bicarbonate ions. The bicarbonate only slightly changes (a small amount) via hydrolysis by water to form carbonic acid and a hydroxyl ion. The resulting solution is only slightly alkaline, a pH of around 8.2.
The resulting hydrolysis and resulting pH can be affected by other ions in solution. One of the problems of using sodium bicarbonate over time is that it changes the composition of the conservative elements in seawater. Its use demands that we do regular water changes to avoid depletion and ratio changes of the essential conservative elements in seawater mixes on a frequent regular basis. Craig Bingman has a study using a computer model where many of the conservative elements change their quantities in seawater due to dilutional effect and consumption and elimination. If borate is one, then the buffer capacity of seawater is further diminished, leaving mostly bicarbonate and carbonate to handle the acid/base reactions.
the baking soda was doing what it was supposed to do. At best, this solution will dissociate further to form the carbonate ion, which in association with sodium will form a very basic solution (Na CARBONATE dissociates in water to a pH of 11.6, very basic). As the dissociation of bicarbonate to carbonate is very small, this is of little significance if there are a large amount of organic acids in the water column, as the bicarbonate (predominant specie in this reaction) will be consumed by the acids, driving carbonate back to the reactant bicarbonate and further dropping pH.
So what do these things mean to us? When adding sodium BICARBONATE to the system, if there were no other ions, the pH would only be 8.2, not a lot to affect a pH of 8.1 much to start with. If there are significant amounts of organic acids in the water column, they will quickly react with the bicarbonate ion to form the neutral form of that acid and release carbon dioxide gas into the water column. This results in a rapid drop of the pH of the water column due to the formation of carbonic acid and a depletion of the buffer capacity of the solution, not what we might expect when adding baking soda. However, in the presence of adequate amounts of calcium, and the presence of carbonate ions, the pH would be maintained, and bicarbonate is conserved rather than consumed to maintain alkalinity/buffer of the water column. This is why most reef buffer builders contain 8 parts sodium bicarbonate and 1 part sodium carbonate The high pH of the carbonate helps offset the resulting release of carbon dioxide which leads to the formation of carbonic acid in seawater reactions. Sodium Bicarbonate by itself is so slightly alkaline that it fails to turn phenolphthalein indicator red. Sodium Carbonate, on the other hand, turns phenolphthalein dark red due to it's extensive ionization in water. In addition, the carbonate is now available to replenish the bicarbonate ion in the water column, further conserving alkalinity of our seawater."
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