CYA Level

[imaslyanchuk]

So after always being not sure when is the dot actually considered gone during the test. I bought R-7065 CYA standard to test for how it should look. The standard solution is calibrated to 50ppm CYA.
After doing the test with standard solution this is what it looks like at 50ppm in test tube:





I can still see the black dot. I always thought the dot should not be visible. At least this gives me a little better idea of what it should look like.

 

[Mdragger88]

Try taking it outside, sun shining, with your back to the sun . It may be a dab less visible & a little more as described in the directions -
"when the black dot just disappears" which to me kinda means “when the black dot is barely still visible but occluded”

 

[Toxophilite]

Is there a light source in front of you? It's an opacity test, so is subjective to eye and lighting. But, after doing mine for so long, I can almost read from the side. The degree of cloudiness becomes discernible before I even look at the dot's end. I would easily call that 50 based on what my 40 always looks like. 40 will block completely, so would be called a 50.

 

[Newdude]

Your eyes adjusting to the test vial with a (quick) glance is part of the test. It's partly why staring usually let's you see the dot because your eyes have time to focus. So pics really can't mimic the test IMO.

Try it outside, and take a flash of a glance. What you see (we all see it differently) is what you need to repeat.

 

[revitup]

Your eyes adjusting to the test vial with a (quick) glance is part of the test. It's partly why staring usually let's you see the dot because your eyes have time to focus. So pics really can't mimic the test IMO.

Try it outside, and take a flash of a glance. What you see (we all see it differently) is what you need to repeat.

Or always perform the test under the same light source, whether outdoors with back to the sun or whatever, or under a 4’ fluorescent garage light as I do.

 

[Newdude]

@revitup has a great point that consistency is key, but also an inadvertant point that armed with a calibrated sample, you can train yourself to use any well lit area. Once you know what 50 looks like under your light of choice, repeat that opacity for future tests.

 

[wayner]

I agree that this test is HORRIBLE. It is really subjective to say when you can't see the black dot anymore. Especially at higher CYA levels. I have to think that accuracy is something like +/- 10-20 ppm at levels above 50