How to include a vertical space between two chemfig reaction schemes in a TikZ box

Question

This is a continuation of my previous question. I am dealing with the following code to include chemical reactions into the shape of a cloud.

\documentclass{article}
\usepackage{chemfig}
\usepackage{tikz}
\usetikzlibrary{shapes}

\newsavebox\ReactionBox
\sbox\ReactionBox{
\tiny
\setchemfig{compound style={draw,line width=0.8pt,
semitransparent,text opacity=1,inner sep=3pt,
rounded corners=1mm}}
\schemestart[0,1,line width=0.6mm]
$A + B$ \arrow([fill=cyan]--[fill=cyan]){->[k_1]}[,,green] $C$
\schemestop  

\schemestart[0,1,line width=0.6mm]
$C$ \arrow([fill=cyan]--[fill=cyan]){->[k_2]}[,,green] $D$
\schemestop  
}


\begin{document}
\begin{tikzpicture} 
    \node [align=center,cloud, draw,cloud puffs=10,cloud puff arc=120, aspect=2, inner ysep=2em] 
    {\usebox\ReactionBox};
\end{tikzpicture} 

\end{document}

The problem is that both reactions appear next to each other instead of one above the other. How to go about fixing this?

Answer 1

One way would be to use two \saveboxes:

The problem has nothing to do with tikz as can be seen if you simply use \usebox\ReactionBox.

Notes:

• You were missing a few tailing % which were resulting in a few spurious spaces. For a good example of what can go wrong if you ignore these see Tex Capacity Exceeded (if remove % after use of macro).

Code:

\documentclass[border=2pt]{standalone}
\usepackage{chemfig}
\usepackage{tikz}
\usetikzlibrary{shapes}

\newsavebox\ReactionBoxA
\newsavebox\ReactionBoxB
\sbox\ReactionBoxA{%  <-- Added %
\tiny
\setchemfig{compound style={draw,line width=0.8pt,
semitransparent,text opacity=1,inner sep=3pt,
rounded corners=1mm}}% <-- Added %
\schemestart[0,1,line width=0.6mm]
$A + B$ \arrow([fill=cyan]--[fill=cyan]){->[]}[,,green] $C$
\schemestop}

\sbox\ReactionBoxB{%
\tiny
\setchemfig{compound style={draw,line width=0.8pt,
semitransparent,text opacity=1,inner sep=3pt,
rounded corners=1mm}}%  <-- Added %
\schemestart[0,1,line width=0.6mm]
$C$ \arrow([fill=cyan]--[fill=cyan]){->[]}[,,green] $D$
\schemestop}


\begin{document}
\begin{tikzpicture} 
    \node [align=center,cloud, draw,cloud puffs=10,cloud puff arc=120, aspect=2, inner ysep=2em] 
    {\usebox\ReactionBoxA \\ \usebox\ReactionBoxA};
\end{tikzpicture} 

\end{document}