CYA standard testing

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D

dnh

0
Mar 27, 2015
16
Richardson
Last fall, I got some of the 50ppM CYA standard to help me test the CYA. When I used it for a CYA test I saw that the black dot had to really disappear to find the correct reading.

Today I rechecked with the standard and the black dot disappears around 80-70, not 50. I did this at first outside in sunlight with my back to the sun, but even in full sunlight, the dot is still not visible at 70.

Is there an expiration on the standard? OR maybe I have done something else wrong. I filled the test bottle to the bottom of the label with the standard, and then to the top of the label with the reagent, I did overshot and went just above the label with the reagent. Shook it for 30 seconds and then tested. What am I missing?

thanks

Don
 
I would say that the standard solution should be good for at least 18 months. What I have told folks in the past is this: Assume that the 50ppm solution is right. That means you need to adjust your environment until you get a reading of 50. In your case, you need a little more light than before. Like Richard said, watch your finger placement.
 
Duraleigh says, oh great lefty's on here commenting about CYA testing again :rolleyes:.

+1 on all the comments posted here. CYA testing can be a pain. I sometimes use the standard to get a reading, then rinse and do the real test right after to have a reference point. Richards two finger method made a big difference in what I saw when testing.

By the way, my standard solution is almost a year old and is still good despite (don't tell anybody) that it sat out in the shop all winter during some very cold days.;)

P.S- Dave will like this, I'm thinking of getting another bottle and test tube and doing real and standard testing simultaneously to get a REAL accurate reading. I know overkill :)
 
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