Around the year 1775 industrial age chemists discovered that if you expose pearlash (potassium carbonate) to carbon dioxide gas the result was potassium bicarbonate, a compound that’s about twice as potent as regular old pearlash. The creation was dubbed “saleratus”, a Latin word meaning “aerated salt.” The discovery prompted an American entrepreneur by the name of Nathan Read to try making the stuff, which he did by suspending pearlash over vats of fermenting rum which produce — you guessed it — CO2. Very clever indeed. Read’s saleratus came on the market in 1788. But the stuff never really caught on as a leavener, mostly because it wasn’t terribly pure and hence not very reliable.
A purer, higher quality saleratus was available from Europe at the time. It was chemically different but made via a similar process, namely by exposing another carbonate compound — this time sodium carbonate or “soda ash” — to carbon dioxide gas. Since that saleratus was imported, however, it was a more expensive product than most American home bakers could afford. Which is why, in 1846, American entrepreneurs Austin Church and John Dwight decided it was time to make the stuff domestically. Their product, called “Dwight’s Saleratus”, was made in the European style, meaning that it was actually sodium bicarbonate, what we now call “baking soda”. That term didn’t come into common use until the 1920’s however, which is why many cookbooks dating to the era still use the term “saleratus”.