The image just to the right is a 23K GIF of him. He was awarded the first Nobel prize in chemistry in 1901 and the ChemTeam thinks this is the official portrait selected from the many pictures taken at the photo session. From the late 1870's to the turn of the century, van 't Hoff was one of the premier chemists in the world.
T is temperature, measured as usual in Kelvins.
Once again, i is called the van 't Hoff factor. The van 't Hoff factor is a unitless, empirical constant related to the degree of dissociation of the solute. The value is unitless. That means it is just a number like 1 or 2. Empirical means we must determine it by experiment.