Remove white line through table

Question

I am new to LaTeX and trying to draw a table. I have followed a couple of guides and found solutions to problems I was having on here but I can't find anything to help me remove the white lines I have running through my table and to the left of the second row.

Please can someone help me?

\documentclass[paper=a4, fontsize=11pt]{scrartcl}

\usepackage{multirow, booktabs} 
\usepackage{array} 
\usepackage[table]{xcolor} 

\newcolumntype{x}[1]{%
>{\centering\hspace{0pt}}p{#1}}%

\definecolor{myblue}{RGB}{122, 140, 213}

\renewcommand{\arraystretch}{1.5}
\begin{center}
\begin{tabular}{|x{3cm}|x{3.5cm}|x{3.5cm}| }\hline
\rowcolor{myblue!50}  & \multicolumn{2}{|c|}{Concentration of Sodium Hydroxide Added /M} \\ \cmidrule{2-3}
\rowcolor{myblue!50} \multirow{-2}{*}{Sample Number} & Drop 1 (left) & Drop 2 (Right)\tabularnewline\hline
 1 & 0.01 M & 1.00 M \tabularnewline\hline
 2 & 0.05 M & 0.10 M \tabularnewline\hline
 3 & 0.10 M & 0.01 M \tabularnewline\hline
 4 & 0.50 M & 0.05 M \tabularnewline\hline
 5 & 1.00 M & 0.50 M \tabularnewline\hline
\end{tabular}
\end{center}

Answer 1

I would use \hhline rather than \cmidrule, and split the \multicolumn in two lines:

\documentclass[paper=a4, fontsize=11pt]{scrartcl}

\usepackage{multirow, booktabs, hhline}
\usepackage{array, hhline}
\usepackage[table]{xcolor}

\newcolumntype{x}[1]{%
>{\centering\arraybackslash}p{#1}}%

\definecolor{myblue}{RGB}{122, 140, 213}

\begin{document}

\renewcommand{\arraystretch}{1.5}
\begin{center}\setlength{\aboverulesep}{0pt}\setlength{\belowrulesep}{0pt}
\begin{tabular}{|x{3cm}|x{3.5cm}|x{3.5cm}| }\hline
\rowcolor{myblue!50}[\tabcolsep][\dimexpr\tabcolsep +0.4pt] & \multicolumn{2}{p{\dimexpr7cm + 2\tabcolsep}|}{\centering Concentration of Sodium Hydroxide\newline Added /M} \\[-0.04 pt]
 \hhline{|>{\arrayrulecolor{myblue!50}}->{\arrayrulecolor{black}}|--|}\noalign{\vskip-0.04pt}
\rowcolor{myblue!50}\multirow{-2.}{*}{\cellcolor{myblue!50}Sample Number} & Drop 1 (left) & Drop 2 (Right)\tabularnewline
\hline
 1 & 0.01 M & 1.00 M \\ \hline
 2 & 0.05 M & 0.10 M \\ \hline
 3 & 0.10 M & 0.01 M \\ \hline
 4 & 0.50 M & 0.05 M \\ \hline
 5 & 1.00 M & 0.50 M \\ \hline
\end{tabular}
\end{center}

\end{document} 

Answer 2

I would remove not only the white line but also (a) all vertical rules and (b) almost all horizontal lines. Your table will be much more readable as a result of the proposed simplifications.

\documentclass[paper=a4, fontsize=11pt]{scrartcl}
\usepackage{multirow, booktabs, array}
\usepackage[table]{xcolor}
\definecolor{myblue}{RGB}{122, 140, 213}

\newcolumntype{x}[1]{>{\centering\arraybackslash\hspace{0pt}}p{#1}}
\renewcommand{\arraystretch}{1.25}

\begin{document}
\begin{center}
\begin{tabular}{x{3cm}x{4cm}x{4cm} }
\rowcolor{myblue!50}  & 
\multicolumn{2}{c}{Concentration of Sodium Hydroxide Added /M} \\ 
\rowcolor{myblue!50} \multirow{-2}{*}{Sample Number} 
& Drop 1 (left) & Drop 2 (right) \\
 1 & 0.01 M & 1.00 M \\
 2 & 0.05 M & 0.10 M \\
 3 & 0.10 M & 0.01 M \\
 4 & 0.50 M & 0.05 M \\
 5 & 1.00 M & 0.50 M \\
\bottomrule % <-- new
\end{tabular}
\end{center}
\end{document}

Answer 3

I take it you are using \cmidrule because \cline gets covered with color. The good news is that the gaps above and below \cmidrule can be set using \aboverulesep and \belowrulesep. The bad news is that I haven't figured out how to make temporary changes in the middle of the tabular without getting a "misplaced \noalign" error.

Now the only problem is the gap due to the \multicolumn being wider than the normal columns.

\documentclass[paper=a4, fontsize=11pt]{scrartcl}

\usepackage{multirow, booktabs} 
\usepackage{array} 
\usepackage[table]{xcolor} 

\begin{document}

\newcolumntype{x}[1]{%
>{\centering\hspace{0pt}}p{#1}}%

\definecolor{myblue}{RGB}{122, 140, 213}

\renewcommand{\arraystretch}{1.5}
\begin{center}
\aboverulesep=0pt
\belowrulesep=0pt
\begin{tabular}{|x{3cm}|x{3.5cm}|x{3.5cm}| }\hline
\rowcolor{myblue!50}  & \multicolumn{2}{c|}{Concentration of Sodium Hydroxide Added /M} \\
\cmidrule{2-3}
\rowcolor{myblue!50} \multirow{-2}{*}{Sample Number} & Drop 1 (left) & Drop 2 (Right) \rule{0pt}{\dimexpr \arraystretch\ht\strutbox+2pt}
\tabularnewline\hline
 1 & 0.01 M & 1.00 M \tabularnewline\hline
 2 & 0.05 M & 0.10 M \tabularnewline\hline
 3 & 0.10 M & 0.01 M \tabularnewline\hline
 4 & 0.50 M & 0.05 M \tabularnewline\hline
 5 & 1.00 M & 0.50 M \tabularnewline\hline
\end{tabular}
\end{center}
\end{document}

Answer 4

Just for fun with TikZ.

\documentclass[tikz,border=5mm]{standalone}
\begin{document}
\newcommand{\col}[6]{
\path #1  node{#2}
++(-90:1) node{#3}
++(-90:1) node{#4}
++(-90:1) node{#5}
++(-90:1) node{#6};
}% end of \col command
\begin{tikzpicture}[xscale=4,yscale=.6]
\begin{scope}[shift={(-.5,.5)}]
\draw[teal] 
(0,0) grid (3,-5)
(0,0) rectangle (3,2)
(1,1)--+(0:2) (1,0)--+(90:2) (2,0)--+(90:1);
\end{scope} 
\col{(0,0)}{1}{2}{3}{4}{5}
\col{(1,0)}{0.01 M}{0.05 M}{0.10 M}{0.50 M}{1.00 M}
\col{(2,0)}{1.00 M}{0.10 M}{0.01 M}{0.05 M}{0.50 M}
\path
(0,1.5) node{Sample Number}
(1,1)   node{Drop 1 (left)}
(2,1)   node{Drop 2 (right)}
(1.5,2) node{Concentration of Sodium Hydroxide Added /M};
\end{tikzpicture}
\end{document}

In the above code, if you use

\begin{scope}[shift={(-.5,.5)}]
\fill[cyan!30] (0,0) rectangle (3,2);
\draw[cyan] (0,-5)--+(0:3);
\end{scope} 

then you get