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Re: Seachem phosphate test kit

>You kind of answered a question I was going to pose to
>you before I asked it with your last post.  I should
>go with whatever the kit says at 30 seconds regardless
>of any change that might take place after that?  The
>color will often keep giving a higher and higher
>reading until it gets to about .5 ppm, when it then
>changes to a pale turquoise color that doesn't match
>anything on the slide.  For a while, I was thinking
>that whatever reading I got before it turned to
>turquoise was the right one.  Not so?

Correct, because before it turns turquoise even then the green color 
that it is at is not the same hue of green on the color scale (more 
blue green and less yellow green). As long as the hue of green 
matches the hue on the scale you're ok to take a reading, but as soon 
as that hue changes it's not valid and would be read as a false high 
reading. You can play around with the reference to see this more 
clearly under controlled conditions. If you test the reference the 
color develops rapidly and completely in about 10 seconds... you then 
have from 10-20 seconds to read it accurately (i.e. the green hue 
won't change) after that it will keep getting darker and darker which 
would otherwise be read as a false high, however you should notice 
that this "higher" green is not the same hue as the green on the 
scale, it's more blue and less yellow. So, if it doesn't match the 
hue of the scale then it's not a valid reading.

Gregory Morin, Ph.D.  ~~~~~~~Research Director~~~~~~~~~~~~~~
Seachem Laboratories, Inc.      www.seachem.com     888-SEACHEM