Ingredients (for four glasses):
Tools: Chemistry and math (yes, they can be fun ;-)):
- 4*1.6 g baking soda
- 0.3 g soy lecithin
- 5 g citric acid
- 1 pint of apple juice
Baking soda also known as sodium bicarbonate or sodium hydrogen carbonate reacts with an acid to carbon dioxide (among other products):
With citric acid baking soda reacts to trisodium citrate, water and carbon dioxide:
They are the main ingredients in sherbets and responsible for the fizzing. In order to stabilize the carbon dioxide bubbles, soy lecithin is used.
Soy lecithin is a phospholipid, with a hydrophilic 'head' (attracted to water) and a hydrophobic 'tails' (repelled by water). The water-loving ends of the lecithin orient themselves towards the water molecules and thereby stabilize the foam.
In order to calculate the ratio of citric acid to baking soda take a look at the second equation. Citric acid has three protons, therefore for each molecule of citric acid three molecules of baking soda are needed.
3 mol baking soda are 252.03 grams and 1 mol citric acid are 192.43 grams. So if we are using 5 grams of citric acid as in this example we will need about 6.55 grams of baking soda.