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Rex Phosphate
Orange syrup, 1 pint; strawberry syrup, ½ pint; pineapple syrup, ½ pint; phosphoric acid syrup, 2 drams; compound tincture cudbear, 2 ounces; angostura bitters, 2 ounces; citrate caffein, ½ dram. Mix syrup first, then add acid, cudbear and bitters. Add caffein last, after dissolving in warm water.
This is a bulk fountain syrup from the era when the soda counter sat at the back of a drugstore and the dispenser had a pharmacist's scales. Two of its ingredients are pharmacy stock rather than food, which is why it cannot be reproduced.
- Compound tincture of cudbearCudbear is a purple-red dye extracted from lichens (chiefly Ochrolechia and Roccella species) with ammonia, and the compound tincture was an alcoholic colouring preparation kept for tinting medicines. It is not an approved food colour in the US or EU today and is not sold for consumption.
- Citrated caffeineHalf a dram is about 1.9 g of caffeine citrate, roughly 1 g of caffeine, weighed loose by hand. Bulk caffeine powder is the specific hazard here: at these scales a small weighing error is a large dose, and fatalities from mismeasured powdered caffeine are documented. Nothing in the recipe tells you the finished yield or the pour per glass, so the dose per drink is unknowable.
- Phosphoric acid syrupThe "acid phosphate" of the fountain trade was a dilute phosphoric acid solution, sometimes with calcium, sodium and magnesium phosphates, sold specifically for soda work. Two drams by apothecaries' fluid measure is about 7 mL. Laboratory phosphoric acid is not a substitute; concentrated grades are corrosive.
- Angostura bittersThe one ingredient still on shelves unchanged in kind. Two fluid ounces goes into roughly two and a quarter pints of syrup, meant to read as a faint spice bitterness under the fruit.
- Apothecaries' measureA dram is ambiguous in old fountain books: as fluid measure it is about 3.7 mL, as apothecaries' weight about 3.9 g. The acid is almost certainly fluid, the caffeine citrate almost certainly by weight, but the text does not say so.
- What to make insteadIf you want the flavour idea, an orange-strawberry-pineapple syrup with a dash of Angostura over soda water is straightforward. Use a current recipe and leave out the dye and the caffeine.
The "phosphate" was a staple of the American soda fountain from the 1880s into the early twentieth century: a shot of fruit syrup, a few drops of acid phosphate for tartness, and carbonated water drawn from the counter. Fountains competed on proprietary house mixes, and grandiose one-word names were part of the sell. The citrated caffeine here suggests the drink was meant as a mild stimulant sold in a drugstore, in the years when the line between a soft drink and a patent remedy was still being drawn. Federal food regulation from 1906 onward gradually tightened control of both dyes and added alkaloids in formulas of this kind.