Salifert kit color indicators: How do they work?

[ZzyzxRiver]

I understand enough chemistry to know that a chemical reaction can cause a solution to change colors, but what I don't understand is how all of the salifert kits manage to be the same pink and blue color, when different things are reacting each time. Anybody know how that works?

 

[Randy Holmes-Farley Verified Community Expert]

I understand enough chemistry to know that a chemical reaction can cause a solution to change colors, but what I don't understand is how all of the salifert kits manage to be the same pink and blue color, when different things are reacting each time. Anybody know how that works?

Alk kits are pH indicator dyes. Endpoint is around pH 4.2 and Salifert is likely a mix of dyes.

Calcium and magnesium kits are dyes that change color when bound to calcium or magnesium. The titration is a strong binder like edta that strips them off the dye, changing the color. The calcium kit is interfered with by magnesium, so it is precipitated first at high pH.

 

[Dan_P]

I understand enough chemistry to know that a chemical reaction can cause a solution to change colors, but what I don't understand is how all of the salifert kits manage to be the same pink and blue color, when different things are reacting each time. Anybody know how that works?

Maybe the color pink showing up is a coincidence rather than a deliberate choice of chemistry to always produce pinkish colors.