Food grade Baker’s Ammonia predates baking powder and baking soda as a leavening agent. Used first in Scandinavia regions to make light pastries and types of cookies. It continues in use today where required in old-fashioned recipes where crisp and light cookies etc. are wanted. Online, one reads that “Icelandic air biscuits” cannot be made airy and light with anything other than ammonium carbonate. The strong ammonia smell produced during baking will dissipate when cookies are done.