That formula is for a ready to use, one-shot intensifier. It
works well. You bleach the negative in the solution and then
redevelop in something like Dektol.  Kodak IN-4 chromium
intensifier Water 1 l Potassium dichromate 90 g Hydrochloric
acid (conc) 64 ml Dilute 1:10 for use. Bleach negative
thoroughly in the above solution. Wash 5 minutes, then redevelop
in room light in a non-staining developer without excess
sulfite. Degree of intensification may be controlled by degree
of redevelopment. After redevelopment, rinse negative, fix, and
wash. Repeat process for greater effect.