Hydrochloric acid enzyme pepsin by self-cleavage. After leaving the stomach, the hydrochloric acid of the chyme is neutralized in the duodenum by sodium bicarbonate. The stomach itself is protected from the strong acid by the secretion of a thick mucus layer, and by secretin induced buffering with sodium bicarbonate. Heartburn or peptic ulcers can develop when these mechanisms fail. Drugs of the antihistaminic and proton pump inhibitor classes can inhibit the production of acid in the stomach, and antacids are used to neutralize excessive existing acid. Concentrated hydrochloric acid (fuming hydrochloric acid) forms acidic mists. Both the mist and the solution have
Break key scancodes at all on release; therefore it is not possible for any software to determine whether this key is being held down. On modern keyboards, the key is usually labeled "Pause" with "Break" below, sometimes separated by a line: formula_1, or "Pause" on the top of the keycap and "Break" on the front. In most Windows environments, the key combination brings up the system properties. Compact and notebook keyboards often do not have a dedicated key. These may use the following substitutes for : Substitutes for : Apple keyboards do not have the Pause/Break key, as Mac OS X does