Viola Mint

A fountain syrup rather than a finished drink: you are making a quart of flavoured syrup that gets charged with carbonated water a glass at a time. The whole thing hinges on the strength of the peppermint, since modern extract is not the same product as a 1900 pharmacist's essence.

• Drams and ouncesThese are fluid measures from the drug counter. A fluid dram is one-eighth of a fluid ounce, about 3.7 ml, so 4 drams of peppermint essence is roughly half a fluid ounce and 1 dram of acid is about a teaspoon. The 32 fluid ounces is the finished volume of syrup, not an added quantity.
• Peppermint essenceA pharmacy essence of peppermint was an alcoholic solution of the oil, and period formulas for it are generally much more concentrated than a modern culinary extract; supermarket peppermint oil is stronger still. Strengths vary too much to convert directly, so add a fraction of the half ounce, taste the syrup diluted at fountain strength, and build up. Overshooting is hard to pull back once the quart is made up.
• American Fruit AcidA proprietary acid solution sold to fountains; such preparations were generally solutions of fruit acids, citric most commonly. A citric acid solution does the same job: it sharpens the lemon and keeps the syrup from tasting flat.
• Gum foamGum foam, also sold as foam mixture, was gum arabic (sometimes with saponin-bearing extracts) dissolved in syrup and added to give a soda a lasting head. Powdered gum arabic dissolved in hot simple syrup is the closest honest substitute; the original leaves the quantity to the dispenser, so start with a small addition and judge by how much head you want.
• "Enough syrup"Plain simple syrup, made heavy in the fountain style at roughly two parts sugar to one of water by weight. Combine lemon juice, essence, acid and foam, then top up with syrup to reach a full quart.
• "Dispense solid"Fountain shorthand, most likely directing that the carbonated water be drawn in the coarse or solid stream rather than the fine spray. In a modern kitchen, pour the syrup into the glass first and add cold soda water in a steady stream.
• The colourNothing in the formula is violet, despite the name, and no colouring is called for. Left alone the syrup is pale and cloudy, which is not wrong, only unadvertised.
• YieldOne quart of syrup, dispensed at about 1 to 1.5 fluid ounces per 8-ounce glass, gives roughly 20 to 30 drinks. Keep it refrigerated and use it within a couple of weeks, as the fresh lemon juice will fade before the sugar spoils.