What ㏗ means
It's the boxed form of pH.
The square lets pH occupy one East Asian character cell, following the convention used for Japanese square unit abbreviations and technical shorthand. Early Japanese and Chinese character-code charts carried the form into Unicode.
Chemist Søren P. L. Sørensen introduced the pH concept in 1909. After competing notations, plain pH was broadly accepted in U.S. chemistry by around 1930.
Technical fixed-cell notation carried through East Asian character encodings.
Read it as ordinary pH; keep the box only when matching its fixed-cell source.
Don't confuse it with
1Questions people ask
1Why does ㏗ show as a box on some devices?
Because that device's fonts have no glyph for it. The character is still correct and still copies correctly — the box is a missing glyph, not a broken character.
How to type ㏗
㏗\33D7Codes and encoding1 code points
A visible symbol can contain several code points. JS .length counts UTF-16 units; UTF-8 counts bytes.