Celexa liquid mostly contains the active chemical citalopram, purified water and natural peppermint flavor, plus small amounts of propylene glycol made from two alcohol molecules, and two preservatives methylparaben and propylparaben which are common food additives. If you've ever taken a liquid cough suppressant than you've probably had all these additives in a highly concentrated form.
The branded product contains 2mg citalopram in 2ml of solution, so you'll need to take just over a tablespoon of liquid, mostly water. There is also a generic version containing 10mg citalopram in 5ml (about a teaspoon) of liquid.
Antidepressants in liquid form are mostly prescribed to the elderly who have trouble swallowing. They are also useful in adjusting doses by very small increments when tapering off the antidepressant.