On a Mac:br>
Java applets are no longer working well in the latest operating system using Safari 12.xx.xx. I am working on creating .jnlp version that will work.

If you are using an early version of Safari then follow these instructions: Assuming you have Java installed, go to System Preferences. Near the bottom you will see a Java icon. Open the Control Panel. Go to the Security tab. In the Exceptions Site List select the Edit Site list button. Click on the Add button and enter ‘http://introchem.chem.okstate.edu’, then click the OK button. As of January 26, 2019 you will need to add a second exceptions to the list: http://canyon.okstate.edu. Click OK to exit the Control Panel. You should be able to access the simulation after following these instructions. It is possible you may have to quit your browser and re-open the web site.

If you are using Safari 12.xx.xx you also must also download the runtime version of Java as described above. Next, click on the link to the .jnlp file on the previous page and then follow the instructions in this ‘Help!’ file.