Help with Salifert Calcium kit please?

[otrlynn]

I have been wondering for awhile if I am using the Salifert test kit for Calcium correctly. The test kit instructions say to dose solution number 3 to the test vial until the solution turns "clear blue" (swirling the test vial after each drop). On a recent test I got a distinct change to what I would call purple at 350, what I would term purplish blue at about 370, and true blue at 400. The problem with color is that it is so subjective... I am hoping that I am reading it right and calling it 400. Any help?

 

[jansenwrasse]

It sounds like your Ca is at 400. You want to color change to be completed. If you are unsure about the change add 3 more drops of the #3 to the vial and see if it turns more blue, if not then it was your true endpoint.

Hope this Helps

 

[otrlynn]

Ah, okay that helps a lot. So I want it to be the "final color" or bluest blue?

 

[jansenwrasse]

Correct. Other wise the endpoint becomes to obscure. It should stop changing colors.

 

[otrlynn]

Got it. Thanks!

 

[stingythingy45]

I'm always coming to the end of the syringe when it finaly turns blue.
That's around 500 ppm.