Duplex Cocktail — The Cocktail Ontologist

Variants (2)

The Cocktail Book a Sideboard Manual for Gentlemen (1901, p.27)

3 dashes	orange bitters	base
0.5 portion	French vermouth	modifier
0.5 portion	Italian vermouth	modifier
3 dashes	Acid phosphate	other

Fill a mixing glass with ice and add the ingredients.
Shake well, strain into a cocktail glass, and serve.

Ice: Ice

This is a good marker for the dual-vermouth aperitif field thickening at the same time as dry Manhattan and Martini styles were consolidating.

Like the Brut, the acid-phosphate and shake instruction give it a sharper service profile than a plain stirred vermouth cocktail.

The Ideal Bartender by Tom Bullock (1917, p.40) — Bullock 1917

0.5 jigger	Old Tom gin — Old Tom Gin	base
4 dashes	orange bitters — Orange Bitters	bitter
1 pony	French vermouth — French Vermouth	modifier
1 pony	Italian vermouth — Italian Vermouth	modifier
3 dashes	Acid phosphate — Acid Phosphate	other

Fill a large bar glass with shaved ice.
Shake, strain into a cocktail glass, and serve.

Ice: Shaved ice

This matters because it preserves acid phosphate as an active cocktail-house modifier inside the dual-vermouth field rather than only in soda-fountain drinks.

The phosphate is central to the drink's identity and should not be flattened into generic acidity.

See also: Lone Tree Cocktail, Perfect Cocktail