I want to investigate the pH of soft drinks and the influence of a bicarbonate buffer (such as the one in our saliva) on this. For that I would like to test how much bicarbonate solution is needed to raise the pH of the drinks to 5.5 because this is usually considered the threshold below which tooth erosion occurs. But how do you make the bicarbonate solution? I have baking soda, but I don’t know how much to dissolve in what volume of water to get the right concentration so I don’t have to use too large amounts when titrating.
Answer
Bye Eline
There is actually not really one answer to your question. I’m not making a calculation here, I don’t think that’s really the intention.
You can find a list of the pH of many soft drinks (see for example attached link); the more acidic the drink (the lower the pH) the more bicarbonate (hydrogen carbonate) you will need to add to neutralize it.
We often titrate with a solution with a concentration of 0.1 mol/litre.
For NaHCO3 that is 8.4 g/l. I would make 100ml of that to start.
If you find that you need very little during your first drink, you can go in two directions:
– take more drink (but 50 ml certainly seems more than enough, I wouldn’t go much higher
– dilute the solution of hydrogen carbonate (for example 5 times or 10 times)
If you need a lot, you can take less drink or make a more concentrated solution.
Of course, hydrogen carbonate is not as strongly basic as sodium hydroxide, so you may need a lot to achieve a pH of 5.5.
I hope you can continue like this, otherwise let me know.
Kind regards
Answered by
Dr Marina Vanhecke
analytical chemistry toxicology soil remediation
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