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Grape Phosphate
Mix twelve tablespoonfuls of grape juice, eight tablespoonfuls of orange juice, and four tablespoonfuls of acid phosphate with two quarts of plain syrup. Color with a little red vegetable coloring. Serve four tablespoonfuls to a glass and fill up with carbonated water.
A soda fountain formula rather than a single drink: you build a flavoring syrup, then dispense it two ounces at a time. Everything hinges on understanding that "plain syrup" is fountain simple syrup, which is far heavier than a bar cook's 1:1.
- Plain syrupIn fountain practice this means a heavy simple syrup, usually something closer to two parts sugar to one part water than to a bar cook's 1:1, cooked just enough to dissolve and then cooled; published fountain formulas vary. A 1:1 syrup will likely taste thin and sour against this much acid phosphate.
- Acid phosphateA dilute solution of phosphoric acid with calcium, magnesium and potassium salts, once standard behind every fountain counter and still sold for exactly this purpose. It gives a dry, mineral tartness with none of the fruit flavor citric acid brings. There is no true kitchen substitute; lemon juice changes the drink into something else.
- Tablespoon proportionsTwelve, eight and four tablespoons come to 3/4 cup grape, 1/2 cup orange and 1/4 cup phosphate. Measure the phosphate accurately rather than by eye, as it is the one component that will dominate if overpoured.
- Grape juiceThe recipe says only "grape juice"; in this period that almost certainly meant bottled unfermented juice, most likely Concord, and Concord is the closest match today. White grape juice will give a different flavor and will not carry the color.
- ColoringPurely cosmetic, to keep the purple from going muddy brown once diluted with soda. Modern gel or liquid food color works; a few drops is the whole intent of "a little."
- YieldAbout 2 1/2 quarts of finished syrup, which at four tablespoons a glass serves roughly 38 drinks. Scale down by a quarter or a fifth for home use; the syrup keeps several weeks refrigerated in a clean bottle.
- ServingFour tablespoons is two ounces of syrup in a tall glass, then fill with cold carbonated water. The recipe specifies nothing about ice or pouring order; modern practice is to add the soda in a way that mixes the syrup and to add ice last.
Recipes like this one belong to the era when the drug-store soda fountain was the American public bar's rival and, after national prohibition took effect in January 1920, its legal replacement. Acid phosphate was originally sold as a medicinal tonic in the second half of the nineteenth century, and fountain dispensers took it up because a dash of it made sugar syrup taste bright and finished rather than merely sweet, the way a squeeze of lemon lifts a sauce. Bottled unfermented grape juice was itself a temperance product, often said to have been promoted from around the 1870s onward as the wholesome alternative to wine, and it appears constantly in books of this type.