Soda Syrup
Mix three pounds of granulated sugar and one and one half ounces of tartaric acid. Stir until dissolved in one quart of hot water. Beat the whites of three eggs and add to the syrup when it is thoroughly cold. Stir well and pour into bottles. To serve, add two tablespoonfuls of the mixture to a glass of water, and stir in a quarter of a teaspoonful of bicarbonate of soda.
This is an old soda-fountain trick: an acid syrup in the bottle, bicarbonate stirred in at the glass, and carbon dioxide generated in front of the customer. The syrup as written is not safe to keep, and the reason is the egg.
- Raw egg white, never heatedThe whites go in only after the syrup is "thoroughly cold," so nothing in the process reaches a temperature that would kill Salmonella. The egg is then bottled and, by the recipe's own logic, drawn on repeatedly over days or weeks.
- Ambient storage with no preservative marginThere is no direction to refrigerate, no boiling of the finished syrup, and no stated shelf life. A sugar-and-acid syrup is hostile to many organisms but is not a sterilising medium, and a bottle opened and re-closed at every serving is repeatedly recontaminated. Use a current recipe if you want a fountain syrup.
- Why the egg was there at allWhy the egg is probably there -- the white was most likely added for foam and body, so that the gas released at the glass would hold a head; the recipe itself gives no reason.
- Tartaric acid is a real food acid, but it is potentOne and a half ounces to a quart is a strong solution. Undiluted it is harsh on tooth enamel and mucous membrane; it is not interchangeable spoon-for-spoon with cream of tartar, which is potassium bitartrate.
- The acid-soda reactionThe quarter-teaspoon of bicarbonate at the glass is what makes the drink fizz, neutralising part of the tartaric acid and leaving sodium tartrate behind. This is effervescence, not carbonation under pressure, and it goes flat within a minute or two.
- UnitsA quart here is 32 fl oz; three pounds of granulated sugar is roughly 6 3/4 cups. Two tablespoonfuls make one serving, but note that the finished syrup is considerably more than the quart of water it starts with, so the yield is well above thirty glasses.
Books of this kind are often placed in the years around 1919, when national Prohibition sent American drink writing scrambling for things to put in a glass that were not liquor; "water wagon" is the period idiom for having sworn off drink. The recipe is a home imitation of commercial soda-fountain practice, where syrups were bottled in bulk and the fizz produced at the moment of serving. The casual bottling of raw egg for indefinite keeping is characteristic of the era: refrigeration was uneven, home food safety was largely a matter of smell and habit, and the connection between eggs and Salmonella was not yet part of ordinary kitchen knowledge.