# Align equations at equal sign with more than one &

I guess this is quite a trivial question but upon searching i only found answers explaining align with one & or how to put the whole equation to the left (such as with fleqn). But i want to keep my equation centered (default) but introduce two "tabulators".

I know how to use the {align} or {aligned} environment. It works perfectly fine with only two columns. But when i introduce two & signs (i.e. three columns) the second & sign does not align the two rows anymore but instead everything after the equal sign is aligned to the right insted of at the & sign.

I thought I can use the & as "tabulator" so that rows are aligned at it but this seems to be wrong.

\documentclass[11pt,a4paper]{scrartcl}
\usepackage[ngerman,british]{babel}
\usepackage[utf8]{inputenc}
\usepackage[T1]{fontenc}
\usepackage{graphicx}
\usepackage{amsmath}

\usepackage{chemmacros}
\chemsetup{modules={all}}

\begin{document}
This works perfectly fine
\begin{aligned} Aa &= Bb \\ \Leftrightarrow \quad Cccc &= Dddd \\ \Leftrightarrow \quad Eeeeee &= Ffffff \end{aligned}

But as soon as i introduce three columns, the equals are not aligned anymore
\begin{aligned} & Aa &= Bb \\ \Leftrightarrow \quad & Cccc &= Dddd \\ \Leftrightarrow \quad & Eeeeee &= Ffffff \end{aligned}

same with align instead of aligned
\begin{align}
& Aa &= Bb    \nonumber\\
\Leftrightarrow \quad & Cccc &= Dddd  \nonumber\\
\Leftrightarrow \quad & Eeeeee &= Ffffff
\end{align}
\end{document}


In this case the environment of choice is alignedat, which allows to set the spacings between the columns, which are pairs of “left-right” ones.

\documentclass[11pt,a4paper]{scrartcl}
\usepackage{amsmath}
\usepackage{chemmacros} %formula, spectra, ...
\chemsetup{modules={all},greek=default}

\begin{document}

If I introduce three columns, the equals are again aligned
\begin{alignedat}{2} &\quad& \frac{v_1}{v_2} &= \frac{[\ch{A}]_1^{m_{\ch{A}}}}{[\ch{A}]_2^{m_{\ch{A}}}} \\ \Leftrightarrow&& \ln\frac{v_1}{v_2} &= m_{\ch{A}} \ln \frac{[\ch{A}]_1}{[\ch{A}]_2} \\ \Leftrightarrow&& m_{\ch{A}} &= \frac{\ln(v_1/v_2)}{\ln([\ch{A}]_1/[\ch{A}]_2)} \end{alignedat}

\end{document}


Here the first column contains the \Leftrightarrow symbols, the second column a quad of space, then the main formulas appear.

• That was fast and does what i wanted, thank you :) So, are the align and aligned environments only suitable for adding one "tabulator" resp. two columns ? – Wulfram Dec 9 '16 at 21:23
• @Wulfram They're for “independent” column pairs, which are evenly spaced. – egreg Dec 9 '16 at 21:27
• the limit for align and alignat (and the *ed and "ed" versions) really depends more on the width of the page. the important thing to remember is that they are defined as "left-right" pairs, so only the "even" &s will give you a neat left-alignment. – barbara beeton Dec 9 '16 at 21:29