I've used the Hanna Checker quite a bit and never seen any colored particles precipitate. There is sort or a detailed process you have to follow to make this test work right, consistently:
Fill the vial with the water sample
Prepare the packet (before zeroing out the meter)
- loosen up all the reagent by tapping/squeezing it with your finger while rotating the packet (move the air around)
- hold the packet with one corner down and keep tapping to get all the reagent in one corner
- Cut the packet with a scissors on the 2 top edges (opposite the corner where the reagent is settled)
- open the packet by grabbing the 2 side corners and wiggling it back and forth gently until it opens like a mouth
- this creates a spillway for pouring out the packet, using the top edge where the 2 cut edges meet
Wipe the cuvette with a clean glasses-cleaning cloth
turn on the meter, wait until it reads C1
insert cuvette
Press the button and release
when it zeroes out, it will read C2, the you have exactly 3 minutes to do the following (I use a timer)
- take out cuvette and open
- carefully pour in reagent
- cap cuvette
- with practice, this above process should take about 20-30 seconds.
- hold cuvette horizontal and rock it back and forth. Do NOT shake vigorously. Just keep it rocking to make the air bubble more the reagent back and forth and get it all dissolved. This usually takes right at about 2 minutes - it should all be dissolved. (use a timer)
- wipe cuvette again with glasses cleaning cloth
- insert cuvette into meter
- press AND HOLD button for 3 seconds until the meter reads 3:00 and then starts counting down.
Now the hard part is over. Set your timer again for 3 minutes so you don't forget to read the meter, as it will time-out after a few minutes.