2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/87505It is shown that, in Dirac theory, there is a spatial velocity of a free electron which commutes with the Hamiltonian, so it is a conserved quantity of the motion. Furthermore, there is a spatial orbital angular momentum which also commutes with the Hamiltonian and is a constant of the motion.5 pages,latexGeneral Physicstext