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Acid Phosphate from Citric Phosphate
Make a solution the same as if with citric acid.
American Citric Phosphate, 6 ounces; Water, 15 ounces. Dissolve and filter. This is a wholesome and palatable acid phosphate, and is preferable to any in the market. It should be used in a squirt-top bottle.
This is a working stock solution for a soda fountain, not a finished drink: a sour, faintly mineral acidulant that was dashed into glasses of syrup and carbonated water the way bitters go into a cocktail. The whole thing hinges on the first ingredient, which is a proprietary powder rather than a generic one.
- What "American Citric Phosphate" wasApparently a proprietary preparation sold to druggists, most likely combining citric acid with acid phosphates of lime, soda and potash, though the exact formula is not recorded here. It does not appear to be available under that name today. Bottled acid phosphate for bar use is made again commercially and is the sensible substitute; do not improvise with laboratory or technical-grade phosphoric acid, which is not food grade.
- Ounces here are weight and volume bothOunces here are probably weight and volume both -- the six ounces of the compound weighed, the fifteen ounces of water measured as fluid ounces, a little under two cups. The yield is on the order of a pint or a little more of concentrate, which at fountain dosage is a great many drinks.
- "The same as if with citric acid"The book is cross-referring to its plain citric-acid solution rather than repeating the method: dissolve, then filter. It does not specify temperature or standing time.
- FilteringIf the compound contained lime salts, insolubles would cloud the bottle and clog a dasher top, which is presumably why the book calls for filtration. A paper coffee filter or a double thickness of fine cloth does what the druggist's filter paper did; expect it to run slowly.
- The squirt-top bottleA dasher-type bottle that delivers a small measured dash rather than a pour. Use glass with a plastic or cork closure, not metal, which the acid will attack.
- How much goes in a glassThe original gives no dose. Fountain dashes of acid phosphate were small, on the order of a half ounce or less per glass, added to the syrup before the soda water so it mixes rather than foams over.
- Keeping itAn acid solution this strong resists spoilage but will pick up dust and dulls in flavor once opened. Make a smaller batch than the book suggests, keep it capped and cool, and discard it if it goes cloudy again after filtering.
Acid phosphate arrived at the soda fountain from the medicine chest. The commercial preparations are generally traced to Eben Norton Horsford, the Harvard chemist behind Rumford Chemical Works, whose acid phosphate was sold from the 1870s as a nerve and brain tonic on the then-fashionable theory that mental work depleted the body's phosphates. Druggists who dispensed it discovered its real virtue was gustatory: it gives a drink a dry, lingering sourness with none of the fruitiness of citric or tartaric acid, and it made cheap syrup taste more substantial. Whole families of fountain drinks were built on it, the chocolate phosphate and the cherry phosphate chief among them, and the word "phosphate" survived on menus long after anyone believed the tonic claims. This entry is a druggist's economy: rather than buy acid phosphate ready-mixed, the fountain man compounds his own from bulk powder and pronounces it better than what he could purchase, which is very much the voice of the trade manuals of the period.