I assume that these are the same dyes that you recommend for the dye bleach color emulsion described on page 171 of your book, "Photographic Emulsion Making, Coating and Testing".

Looking at internet images of the structures, Solantine Yellow (C.I. 13950) appears to be an azo dye with two SO3 groups; Solantine Pink (C.I. 25380) appears to be a diazo with four SO3 groups and two aniline groups. The dye called Chicago Blue appears to refer to two structures, Chicago Blue 4b and Chicago Sky Blue. From what I can tell it also has azo groups with four SO3 groups. I can't find a C.I. number for Chicago Blue. All this is consistent with acid dyes which can be reduced and made colorless in the dye bleach process outlined.

Their diffusion properties are interesting. Do they stain untanned gelatin and not tanned gelatin? Has anyone tried staining a dry gelatin tanned matrix? Could the diffusion rate be regulated by Ph?

It is surprising to see the great interest people have shown in Capstaff's two color photography. Incidentally, I am looking forward to getting volume two of "Photographic Emulsion Making" and learn more about color emulsions. I hope you're not being threatened with being chained in the barn until you finish writing it.