The Time Thing

[kube]

Any one ever notice as you test your water (ammonia in pretcular) that as it sets the color of the test continues to changes, today i set a timer to get it right down to the minute, the test kit says wait five minutes, so i followed the directions to the t set the timer for 5 minutes, the water at five minutes was bright yellow (yellow no ammonia, green lots of ammonia) the i just let it set there, its been oh 2 hours and now its greenish, any one ever think that the longer you wait the better the results or do yo wait the 5 minutes and call it good, or am i just putting to much thought into this simple matter, thanks

 

[reefkprz]

the time thing is for most accurate reading, after x amount of time exposed to air some of the chemicals used in the test evaporate say two hours would be enough to throw the chemical balance thouroughly skewing the test. 5 minutes is to allow the chemicals to thouroughly react, without going so far as to let any overt reaction from the surrounding environment.
here's a test for you, mix two ampules of the same test from the same water leave one capped the other uncapped see wich one changes the most over 2 hours, then do the same thing except leave both capped and set one in direct sunlight the other in shade, then try it again set one in the fridged and one on top of it.
you'd be amazed at how many factors can slightly skew an ammonia test.

 

[mynameis]

leaving the solution in for that long of a time can cause precipitation. This will adhere to your glass/plastic and give you inaccurate readings in the future. Just a thought

 

[geridoc]

I'm sorry, but none of you are correct in your interpretations of why the color changes, and what it means. The chemicals in the test kit react with the target (ammonia, whatever), and turn color in an ongoing reaction that produces more color as time progresses. However, someone has taken a known amount of target, run the reaction for a known amount of time and then determined the exact color at that time. That color is what you see on the comparator card. It is only valid at that time point, not earlier or later. When you see a zero amount at the key time point, and get a positive reading later, that just means that there was a trace amount, too little to measure at the pre-determined time point, so it is effectively zero, but there may still be some there. The amount, while not zero, is too low to affect your fish, so don't worry!