I know it is an old topic but I don't quite get it with this colour change, must be missing something
40 ppm IS reduced -> 40 ppm Colloidal Silver then add saline -> instant colour change (electro static repulsion destroyed, bigger particles -> change in colour)
20 ppm Colloidal Silver then add saline -> hardly any noticeable colour change
As I understand the 40 ppm Colloidal Silver there is very noticeable colour change, but with half concentration hardly colour change. Is that less agglomeration, I am thinking half concentration perhaps expect "half noticeable' colour change?
20 ppm IS add saline -> instant silver cloride coming out of solution, white fog in beaker or settle on bottom? But whichever should that not be readily noticeable.