“M”是溶液物质的量浓度mol/L
standard line notation for electric cell is:
1) write anodic reaction on left,and cathodic reaction on the right,separated with a double vertical line.
2) use single vertical line to indicate phase change (for sick of the phase potential difference）
3）label concentration,state,etc
For example,in the sample you have,
Hg(l)|Hg2Cl2(s)|KCl(sat.)||醌氢醌 solution (pH=?,sat.)|glass electrode
Another example:
Cd(s)|Cd2+（0.1 M)||Fe3+(0.1 M),Fe2+(0.1 M)|Pt