When the color changes

[shingles]

Question: when testing the water and we are looking for color to change from x to y... are we talking about when it changes and stays changed, or just when it flashes?
For example: the TA test says from green to red. If it's green to flash of red (but then goes back to green), I am getting TA of 50. If it's green to red and stays, then I am getting a TA of 70.

thanks,
-S

 

[Donldson]

Changes and stays for more than a couple seconds. I add that caveat because if you leave the FAS-DPD test sit after you finish it does turn back to pink after a couple minutes. But for the TA and CH tests you want the color to change and stop changing. Meaning for TA even after it turns red add another drop to see if it gets redder. When you add a drop to the red solution and it does not change color then you are done with the test. You disregard the final drop that caused no change when doing the math to figure out your TA.

 

[JoyfulNoise]

Do you have a SpeedStir? A SpeedStir makes it very easy as you can get the drops going at a rate of about 1 droplet per second or so and just keep your eyes on the tube without looking away. This lets you see the subtle changes in color, especially with the CH test blue endpoint, much easier.

 

[shingles]

Thanks. I do use a speed stir. I agree it is much easier.