Acid Phosphate.

It is a liquid food additive made of phosphoric acid buffered with mineral salts like calcium, magnesium, and potassium, used to add tartness to drinks.

It has an almost indefinite shelf life if stored in a cool, dark place and kept tightly sealed.

While lemon juice provides acidity, it also adds a strong citrus flavor. Acid Phosphate provides pure tartness without the citrus taste.

Yes, it is food-grade and safe when used in the small quantities typical for beverages and cooking.

No, Acid Phosphate is calorie-free and sugar-free, making it a great option for low-calorie drinks.

It was a staple of 19th-century soda fountains but fell out of fashion in the mid-20th century until it was recently revived by cocktail enthusiasts.

Look for products specifically labeled as food-grade and intended for beverage use, typically sold by specialty cocktail supply companies.

It is rarely used in baking; its primary use is in liquids where a clean, sharp acidity is desired without extra moisture or flavor.

Yes, it is composed entirely of minerals and phosphoric acid, containing no animal-derived ingredients.

The most famous is the 'Phosphate' soda (like a Cherry Phosphate) and various classic pre-Prohibition cocktails.