The early work on CS as a bactericide was done by Henry Crookes. He counted bacterial colonies on gelatin and agar in Petri dishes treated with a sequence of dilutions of CS. As a control, Crookes used a sequence of dilutions of corrosive sublimate as the comparative bactericide. (Needless to say, corrosive sublimate is a very nasty compound, to bacteria and humans alike.) Crookes was astonished that corrosive sublimate and colloidal silver were about equally potent in killing bacteria!
Maybe this Petri plate method is again an objective way to calibrate the potency of EIS. Matthew
