  The derivations of the Cheng-Kac Jordan superalgebras are studied. It is
shown that, assuming -1 is a square in the ground field, the Lie superalgebra
of derivations of a Cheng-Kac Jordan superalgebra is isomorphic to the Lie
superalgebra obtained from a simpler Jordan superalgebra (a Kantor double
superalgebra of vector type) by means of the Tits-Kantor-Koecher construction.
This is done by exploiting the S4-symmetry of the Cheng-Kac Jordan
superalgebra.
