Write cursive l letter in chemical formula with chemmacros package

Question

How can I replace the letter l in HCl with ℓ so it becomes HCℓ when using chemmacros? I would like to avoid confusion between l, 1 and I which look very similar.

Answer 1

First things first: chemmacros does not provide chemical formulas. With standard settings it loads the package chemformula so lets assume you meant that package.

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You can tell chemformula to use ℓ instead of l. Of course you need a font that has the letter. Compiled with LuaLaTeX this example gives:

\documentclass{article}
\usepackage{libertine}
\usepackage{chemformula}
\NewChemCompoundProperty{l}{ℓ}
\begin{document}
\ch{HCl + 1 I2}
\end{document}

Or like @Roland's suggestion:

\documentclass{article}
\usepackage{chemformula}
\NewChemCompoundProperty{l}{$\ell$}
\begin{document}
\ch{HCl + 1 I2}
\end{document}

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BTW depending on the font the real issue might already be solved by itself:

\documentclass{article}
\usepackage{libertine}
\begin{document}
1lI
\end{document}

Answer 2

One option:

\documentclass{article}
\usepackage{chemmacros}
\begin{document}
\ch{HC$\ell$}
\ch{HC$\ell$ + NaOH -> NaC$\ell$ + H2O}\par



\end{document}

UPDATE: Maybe the \ell from stix font package is more like you want it:

\documentclass{article}
\usepackage{stix}
\usepackage{chemmacros}
\begin{document}
\ch{HC$\ell$}\par
\ch{HC$\ell$ + NaOH -> NaC$\ell$ + H2O}\par
\end{document}