Fold in a white paper one drachm of Rochelle salts. In a blue
paper a mixture of twenty grains of tartaric acid, and twenty-five
grains of carbonate of soda. They should all be pulverized very
fine. Put the contents of the white paper into a tumbler not quite
half full of cold water, and stir it till dissolved. Then put the
mixture from the blue paper into another tumbler with the same
quantity of water, and stir that also. When the powders are
dissolved in both tumblers, pour the first into the other, and it
will effervesce immediately. Drink it quickly while foaming.