I would like to ask how to typeset the equation number like Charles's law in the picture? There is a \circ after the closing parenthersis. Do I need another package to do that? The packages that I am using are chemfig, mhchem and graphicx. Thanks a lot.

I am sorry that I cannot figure it out after reading Custom equation numbering. I would like to have the equation numbering like it in the picture.


Boyle's law

pV &= constant,\text{ }at\text{ }constant\text{ }n, T\\

1 Answer 1


I'd like to suggest that you load the mathtools package -- a superset of the amsmath package -- and use its \newtagform and \usetagform macros. (To revert to the default equation tags, run \usetagform{default}.)

enter image description here

\documentclass{article} % or some other suitable document class

\numberwithin{equation}{section} % just for this example

\setcounter{equation}{4} % just for this example

\noindent We assume that \dots
\textup{\bfseries Boyle's law: } pV=\dots \\
\textup{\bfseries Charles's law: } V = \dots \\
\hphantom{\textup{\bfseries Charles's law: }} p = \dots \\ 
\textup{Avogadro's principle: } V = \dots
Boyle's and Charles's laws \dots
  • Thanks so much. I would like to ask if there is code that only affect only 1 equation at a time but not the whole equation? As I still have some other equation that does not have \circ in the numbering.
    – some one
    Commented Jan 8, 2022 at 11:45
  • @someone - Not sure I understand "affect only 1 equation at a time but not the whole equation". (Did you mean to write "...not the whole document"?) You could run \usetagform{Charles} and \usetagform{default} right before and after the "circled" equation in order to limit the scope of the "charles" tag form tp just that equation.
    – Mico
    Commented Jan 8, 2022 at 11:49

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