<a href=showthread.php?s=&postid=11630724#post11630724 target=_blank>Originally posted</a> by phenom5
You put the tank water into the test tube, then add one or more reagents, then add another reagent drop by drop. So for the Ca test you add 2 reagents and those turn the water pink, then you add a third reagent drop by drop until the water turns blue. Then based on how much of reagent #3 is left in the syringe, you get your measurement.