Rebreather World - View Single Post - Chemistry of CO2 Neutralisation - Can weight be used as an indicator of scruber life?

diveoceanos · 1st April 2008, 19:18

The point of this thread is ----> The chemical reaction causes a change in weight inside the scrubber. Is there any way we can use this parameter in any usefull way?

You doubt it. Fair enough!

As for the chemistry I would suspect that we could open a new thread to discuss buffer solutions chemistry and pH index markers. If that is of any interest but I suppose that it is not relevant with this thread and will be not interesting for many people. I can send you by PM or email if you like all the equations in the system with Pkbs and so on but I am not sure if that is what you want. But because you asked me I can tell you a few things about buffer solutions and about carbonate salts solubilities: Na2CO3 is highly soluble in water and gives a lot of bicarbonate anions some CO2 bubbles and sodium positive ions. CaCO3 on the contrary when formed is much less soluble and forms a whitish material virtualy insoluble in water. When CO2 passes through a water buffer system like the one of Ca(OH)2 and NaOH it forms H3O+ that reacts with OH- in the buffer. then the reaction of Ca(OH)2 <-----> Ca++ + 2OH- which is bidirectional (weak base) is shifted to the right. This situation continues until the total concentration of OH- drops (pH decreases) to such a point that a die changes its color (acid form which is pink or whatever other color is being attributed to the acid form of the index chemical used). NaOH provides a certain alkalic pH and it provides a relatively constant alkalic pH throughout thre *life* of the scrubber and it is completely soluble in water. It's quantity is small but this is how buffer solutions work. At the end of scrubber *life* the OH- starts to drop and the buffer solution looses its aility to maintain a constand pH, that's why the color change.

Does this make any difference to the whole issue? I don't think so.

Just to relax your concerns I am aware of how buffer solutions work and one important and necessary element for them to work is water. Therefore water is needed for the reaction inside the scrubber (#1). Any attempt to dry the sorb would definitely had awkward results! But I believe there are no kids reading this forum. I beleive that there are rebreather divers who read this! I can not understand your worries. Where are they based? How did you figured out that anyone could possibly dry out the sorb to weight it and then use it? Where did I write anything like that or where did I write anything that could possibly be perceived as such statement?

1st April 2008, 19:18	#23 (permalink)
diveoceanos New Member Current Rebreather/s: Megalodon Other Rebreather/s: Join Date: Apr 2007 Location: Cyprus Posts: 43	Re: Chemistry of CO2 Neutralisation - Can weight be used as an indicator of scruber l The point of this thread is ----> The chemical reaction causes a change in weight inside the scrubber. Is there any way we can use this parameter in any usefull way? You doubt it. Fair enough! As for the chemistry I would suspect that we could open a new thread to discuss buffer solutions chemistry and pH index markers. If that is of any interest but I suppose that it is not relevant with this thread and will be not interesting for many people. I can send you by PM or email if you like all the equations in the system with Pkbs and so on but I am not sure if that is what you want. But because you asked me I can tell you a few things about buffer solutions and about carbonate salts solubilities: Na2CO3 is highly soluble in water and gives a lot of bicarbonate anions some CO2 bubbles and sodium positive ions. CaCO3 on the contrary when formed is much less soluble and forms a whitish material virtualy insoluble in water. When CO2 passes through a water buffer system like the one of Ca(OH)2 and NaOH it forms H3O+ that reacts with OH- in the buffer. then the reaction of Ca(OH)2 <-----> Ca++ + 2OH- which is bidirectional (weak base) is shifted to the right. This situation continues until the total concentration of OH- drops (pH decreases) to such a point that a die changes its color (acid form which is pink or whatever other color is being attributed to the acid form of the index chemical used). NaOH provides a certain alkalic pH and it provides a relatively constant alkalic pH throughout thre life of the scrubber and it is completely soluble in water. It's quantity is small but this is how buffer solutions work. At the end of scrubber life the OH- starts to drop and the buffer solution looses its aility to maintain a constand pH, that's why the color change. Does this make any difference to the whole issue? I don't think so. Just to relax your concerns I am aware of how buffer solutions work and one important and necessary element for them to work is water. Therefore water is needed for the reaction inside the scrubber (#1). Any attempt to dry the sorb would definitely had awkward results! But I believe there are no kids reading this forum. I beleive that there are rebreather divers who read this! I can not understand your worries. Where are they based? How did you figured out that anyone could possibly dry out the sorb to weight it and then use it? Where did I write anything like that or where did I write anything that could possibly be perceived as such statement? Last edited by diveoceanos : 1st April 2008 at 19:38.
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