Stone- I think the wet plate reference is because the book was written in 1909.
While it may work as a toner, I think it's primarily meant as a negative intensifier. Give it a try with a processed neg you have which needs intensification.
* Forgot to mention that chromium involves a bleach step. My guess is this does, too. And, then, redevelopment. Ian recommends a pyro developer. I seem to recall using dektol when I did it, but it was probably about 30 years ago, and only a couple of times, so I may be misremembering. *
Hmm, I've never done a secondary step, I actually have never done a bleach step independently, I don't even know which kind of beach to use (since there seem to be different kinds) but I'll definitely look into it. Thanks.