Wikipedia says that Ka was a symbol for potassium once.
Current symbol is K.
Name changed due to a standardization of, modernization of, or update to older formerly-used symbol.
When was the symbol for potassium changed from Ka to K? What was the rationale behind that?
Some findings. The INTERNET Database of Periodic Tables's first image with a symbol for potassium is of Charles Daubeny's system using K in 1831. Surprisingly I could not find any use of Ka. But there are many German-speaking books using Ka in the late 19th century, as well as some English ones. More recent findings of Ka: 1894, 1943, 2013