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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{equation}\begin{aligned}
Aa   &= Bb    \\
\Leftrightarrow \quad Cccc &= Dddd    \\
\Leftrightarrow \quad Eeeeee &= Ffffff
\end{aligned}\end{equation}

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

same with align instead of aligned
\begin{align}
& Aa &= Bb    \nonumber\\
\Leftrightarrow \quad & Cccc &= Dddd  \nonumber\\
\Leftrightarrow \quad & Eeeeee &= Ffffff
\end{align}
\end{document}
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1 Answer 1

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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{equation}
\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{equation}

\end{document}

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

enter image description here

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  • 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, 2016 at 21:23
  • @Wulfram They're for “independent” column pairs, which are evenly spaced.
    – egreg
    Dec 9, 2016 at 21:27
  • 1
    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. Dec 9, 2016 at 21:29

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