At the moment it will be a manual injection as and when needed, unless you have any ideas of how it could be cheaply achieved?
And I am hoping that by careful control of the valves the flow rate can be controlled so that it is slow and does not escape all at once. This is something that will require experimentation before I connect to the aquarium however.
To further lower that risk, the concentrations and proportions of the two reactants has been calculated. The target CO2 concentration in the aquarium water is 20ppm or 20mg/L. For a 75 litre aquarium this means that 1500mg (1.5g) is required. As the molecular weight of CO2 is 44.01g/mol, 0.034moles of CO2 is required. The balanced reaction tells us that one mole of sodium bicarbonate and one mole of acetic acid produce a mole of CO2, hence the dose of sodium bicarbonate must be equal to 0.034moles (around 17ml of a 2 molar solution, produced by dissolving 168g in 1litre of water, as it's molecular weight is 84g/mol). Malted vinegar contains 5% w/v acetic acid so the 500ml in the reaction vessel contains just over 0.4 moles (5% w/v gives 25g in 500ml, whilst acetic acid has a molecular weight of 60.05g/mole). This means that there can be over ten doses of sodium bicarbonate before the acetic acid will be depleted and CO2 production will cease.
I am obviously assuming that all carbon dioxide will be diffused successfully and that each dose will last a reasonable amount of time (a few days would mean a month could be achieved before the vinegar would need replacing).
I hope that anyone with experience of using CO2 could point out any major oversights and/or changes needed before I attempt to make this.
The supply of bicarbonate will be manual I unless you can think of a cheap way of automating it? And I am hoping that by control of the valves that the supply can be made to last a decent amount of time sui that it doesn't ask ever the aquarium all at once, but this will require experimentation when one I have made it.
Last edited by Darkblade48; 01-12-2015 at 06:40 AM.
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