Spectra for a given compound are plotted using the controls in the compound window, listed below and described in more detail here. Use the 1H NMR, 13C NMR, IR, Mass and UV/Vis tabs at the top of the graph to switch between the type of spectrum displayed.

Overlay spectra. The compound's spectra are added to the graph, overlaid with any existing plots.
Plot single spectra. Any existing plots are removed and the compound's spectra are plotted alone.
Remove spectra. Remove the compound's spectra from the graph.

Plotting spectra stored in files on your computer

If you grant the SpectraGraph applet permission you can use it to plot your own spectra stored in files on your computer. These can then be directly compared with each other and with spectra from the SpectraSchool libray. SpectraGraph can interpret two-column text and CSV format files and well as many flavours of JCAMP.

To plot a spectrum in this way:

  1. First switch to the appopriate tab eg IR if you intend to plot an IR spectrum.
  2. Now press the Plot filebutton above the graph window. Locate your file and press OK.
  3. To remove your spectrum click its label in the graph and use the Remove spectra button in the Detail window.


Rescaling the graph may be achieved using the toolbar, the keyboard or mouse as detailed below.

Keyboard Mouse
Restore default x range
Home Double-click
Scroll plots left
Left arrow Shift + drag
Scroll plots right
Right arrow Shift + drag
Zoom in
Zoom In
Down arrow, Page Down Shift + click, Click + drag
Zoom out
Zoom Out
Up arrow, Page Up Ctrl + click

Graph toolbar

The other buttons on the graph toolbar have the following functions.

Invert the x axis.
Calculate y range. The range of the y axis is automatically calculated to fit the visible data, so that as new spectra are plotted or the x range changed, the y range is recalculated and thus may change.
Fix y range. This is the alternative to calculate y range above. The y range is fixed at a default value regardless of the data or x axis range.
Plot single spectra. In this mode clicking a compound name in the compound list will remove any other spectra and plot the compound's spectra alone. To compare spectra, select overlay mode using the button below or as described in the compound window.
Overlay spectra. In this mode clicking a compound name in the compound list will add that compound's spectra to those already plotted.. To plot spectra singly, select plot single spectra mode using the button above or as described in the compound window.
Invert Y
Invert the y axis.
Remove all plots. Individual plots may be removed using the controls in the compound window.
Controls the display of the 'helper' plots, described below.
Controls the display of 'hotspots', described below.
Integration traces
Controls the display of 1H integration traces, described below.
Shows the Helpers pop-up window, listing the positions of various common spectral features.
Copy graph
Copy the graph as an image to the clipboard. Requires permission.
Print the graph.
Show this help window.

Helper plots

The helper plots are displayed using the Help button in the graph toolbar. These plots are designed to identify common spectral features.

The information used to display the helper plots may also be viewed using the Helpers pop-up, displayed by clicking the Help toolbar button.

More information about the solvents used in NMR experiments is given under the heading NMR solvents.


A limited number of compounds have 'hotspots'. These are areas of the spectra which when clicked display an image or animation illustrating the structural origin of the peak in question. These compounds are indicated with a Hotspot icon in the library view.

If the spectra for such a compound are plotted then these hotspots may be hidden or revealed by clicking the hotspots button Hotspots in the graph toolbar.

Integration traces

For the 1H NMR spectra integration traces may be displayed using the Integration traces button in the graph toolbar.