Tracey Ruck

The mention of eggshell soda reminds me of "Kenwood Lemonade", from the recipe booklet that came with my mixer 30 odd years ago.
A whole egg, including shell, whole lemon, roughly chopped, sugar and water are liquidized and strained.
The acid from lemon reacts with eggshell to release CO² and produces a very nice foamy and effervescent drink.