The octonion spinor field is studied. The nonassociativeness of the algebra makes it possible to introduce a new quantum number — the associator (partner of the spin) — as a measure of the nonassociativeness and a generator of the Lorentz group. The spin-associator interaction is introduced. This interaction could lie at the basis of the weak interaction of particles. This is proved by the connection found between the associator and the Kobayashi-Maskawa phase factor.