  Data of the radiochemical experiment [E.L.Fireman, 1978] with 1.7 t of
KC_2H_3O_2, accumulated deep underground during ~1 yr, were reanalyzed to set
limits on di-nucleons (nn and np) decays into invisible channels
(disappearance, decay into neutrinos, etc.). The obtained lifetime bounds
tau_np > 2.1 10^25 yr and tau_nn > 4.2 10^25 yr (at 90% C.L.) are better (or
competitive) than those established in the recent experiments.
