Salts

Salts are a chemical substance enclosed in blue bottles which allow the use of Vigors. The player's current Salts level is shown by a segmented blue bar, displaying both the amount of Salts remaining and the number of times the player can cast the currently equipped Vigor before running out.

BioShock Infinite
Booker can find Salts in many places, including Tears, the environment, loot containers, corpses, and Dollar Bill vending machines. Certain consumables such as coffee and soda will also replenish a small portion of the player's Salts, while drinking alcohol will deplete a small amount. Smoking cigarettes will also increase the player's Salts, though at a cost to his or her health.

Salt vials replenish a percentage of the player's Salts bar rather than a fixed amount: a small phial restores 25% of the player's Salts, a medium one gives back 50% and a large bottle or Salts machine fully recharges the player's Salts.

Behind the Scenes

 * Salts are the equivalent of EVE in the previous BioShock games.
 * Salts are likely based on smelling salts, also known as ammonium carbonate, which were used to revive a person if they had fainted (Victorian era women frequently carried smelling salts, as the corsets that were worn at the time restricted breathing and made fainting common.).
 * Though the method of their creation is not stated within the game, an eerily similar liquid can be seen being created above the siphon machine within Monument Island, likely harvested from Tears or from Elizabeth's power.