I'll give that a try, just for the fun of it, and I'll keep looking for information about "standard" markers. If I find anything I'll report back here. Thanks again.

Yes, I saw in the documentation that you can you use pretty much anything as a marker, but if you let Mathematica decide on the markers some of the ones used are a circle, an up triangle, a diamond and so on. I wondered if there is a list somewhere of the "standard" markers. Also can "OpenMarkers" be used in conjunction with, for example, Graphics[Disk[]?

Many thanks for that - your help is much appreciated. A couple of points:

I don't think

Mesh -> All, MeshStyle -> {PointSize[0.01], Default} is still needed

Apart from Disk[] and Rectangle[] what other marker styles are there? And, pushing my luck, do you have any thoughts on the gridlines?

It's really just for the challenge - I like to stretch myself and experiment with what I can achieve (even if I do some help along the way). I know that I can do these things in Excel and I want to be able to do the same things in Mathematica.

Can I ask why you are going to all this trouble to make super-fine adjustments to the plot parameters?Have you been given a style that you are required to match precisely?

I have sorted the axes labels and the legend but gridlines and the style of the plots themselves are still a problem. In particular, PlotMarkers -> {{\[FilledSmallCircle], 10}, {\[FilledSquare], 10}} is changing the marker shape in the legend but not on the plot itself. I am using this to change the size of the markers on the plot

Mesh -> All, MeshStyle -> {PointSize[0.01], Default}

The complete code for the plot is here

Labeled[ListLinePlot[{Reverse[dataPairs1, 2], Reverse[dataPairs2, 2]},
   Frame -> True, PlotRange -> {{0, 20}, {0, 14}}, 
  PlotLabel -> 
   Style["Titration of weak acids with sodium hydroxide", 16, Bold, 
    FontFamily -> Default, FontColor -> Black], 
  PlotLegends -> 
   Placed[LineLegend[{"Acetic acid", "2-chloroaniline"}, 
     LegendFunction -> (Framed[#, FrameMargins -> -2, 
         Background -> Yellow, FrameStyle -> Directive[Red]] &), 
     LegendLayout -> "Row", LegendMarkerSize -> {{10, 12}}, 
     LabelStyle -> {FontSize -> 10}], {Right, Bottom}], 
  ImageSize -> 550, PlotStyle -> {Red, Blue}, 
  PlotMarkers -> {{\[FilledSmallCircle], 10}, {\[FilledSquare], 10}}, 
  Mesh -> All, MeshStyle -> {PointSize[0.01], Default}, 
  GridLines -> {gridLinesF[], gridLinesF[]}], {Style["pH", 12], 
  Style["Vb/\!\(\*SuperscriptBox[\(cm\), \(3\)]\)", 12]}, {Left, 
  Bottom}, RotateLabel -> False]

I have also attached my latest the notebook with what I have got so far. I still need to set the style and size of the markers on the plot, and set the line style of each plot/series. And sort out the grid lines!

Attachments:

V11 Calculation_...nb

To change the legend placement and make it more precise, instead of using defined words like Center, use a formulation like this:

Placed[LineLegend[], {{1, 0}, {1, 0}}]

The first coordinates are scaled to the overall figure (bottom right), and the second coordinates are scaled to the legend itself (also bottom right). So this says to place the legend so that its bottom right corner aligns with the bottom right corner of the graphic. To move it in a bit, you might use

Placed[LineLegend[], {{0.95, 0.05}, {1, 0}}]

Experiment with the numbers and you will get the idea.

Solved #4 with

LegendFunction -> (Framed[#, FrameMargins -> -2, Background -> Yellow,
     FrameStyle -> Directive[Red]] &)

But I would like to know the purpose of # and &