Sealing action in metal salt solutions of nickel acetate, cobalt acetate or potassium dichromate can be assessed by the increasing metal ion content of the sealed film. Typical results are ...

All three patients were patch-tested and had positive reactions to potassium dichromate 0.25% in petrolatum. Avoidance led to the resolution of both the dermatitis and the tattoo inflammation.

Perkin started with a similar chemical to quinine (aniline, or phenylamine) and tried to oxidise it with potassium dichromate. He produced a dark precipitate which seemed to stain anything it ...