Interpreting a recipe from Mrs Beeton: "carbonate of soda"
There are many mentions of carbonate of soda in the Book of Household Management, and also two mentions of bicarbonate of soda (to preserve milk, and in a recipe for light buns). It has a specific section on the carbonate:


  CARBONATE OF SODA — Soda was called the mineral alkali, because it was originally dug up out of the ground in Africa and other countries: this state of carbonate of soda is called natron. But carbonate of soda is likewise procured from the combustion of marine plants, or such as grow on the sea-shore. Pure carbonate of soda is employed for making effervescing draughts, with lemon-juice, citric acid, or tartaric acid. The chief constituent of soda, the alkali, has been used in France from time immemorial in the manufacture of soap and glass, two chemical productions which employ and keep in circulation an immense amount of capital. A small pinch of carbonate of soda will give an extraordinary lightness to puff pastes; and, introduced into the teapot, will extract the full strength of the tea. But its qualities have a powerful effect upon delicate constitutions, and it is not to be used incautiously in any preparation.


It therefore seems likely that the recipe is intended to use carbonate rather than bicarbonate.