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Pet Forum / Aquaria / Marine Reef / September 2004How to read test kits result
Well this might sound like a dump question from the subject but am kind of confused. I went to the LFS to get a calcium test kit and this time i am buying the SeaTest test kit and after a brief conversation with the owner. he told me to test it correctly and i asked him what do u mean by correctly. He said when you add the reagent drop by drop to count how many drops, i should stop when the drop hit the solution in the test tube ( not after you shake or swirl until the reagent has mixed in well with the rest of the test water ). As far as i know, if the reagent is to react with all Calcium ion in the test solution, i should be swirling and shake it to make sure all Calcium ions are reacted to get an accurate reading rather than on at the top portion when the drop hits the water and turns blue. Can someone shed some lights on this. Thx in advance for any help. I'm no expert, and from the sound of it, neither is the LFS owner. In other words, I think that guy is wrong but I'm sure someone else can verify that like boomer. hth ~Mort > Well this might sound like a dump question from the subject but am kind of > confused. [quoted text clipped - 14 lines] > > Thx in advance for any help. i agree, the drops always turn colour on the top bit of water b4 u shake it anway. and then changes all of the water colour when u shake it i dont think it would even posable to have the water change colour b4 u shake it cos it will always change colour when u shake it b4 adding the next drop > I'm no expert, and from the sound of it, neither is the LFS owner. > [quoted text clipped - 27 lines] >> >> Thx in advance for any help. You could always "calibrate" the test yourself: get a sample of water with no Ca (i.e. RO) and add a fixed amount of Ca to it. Now test that water using both methods (and to be "scientific", test a third "control sample" with no added calcium) and see which reads the proper amount against the given test colour. I'd recommend using CaCl2 rather than Ca(OH)2 for this test since it's already in solution and Ca(OH)2 isn't that soluble so you'd have to use a super tiny amount that would be hard to weigh precisely. You'll need to remember some HS stoichiometry of course! I've done this before and it works well (haven't tried it specifically w/ Ca though). Just my 2cents > i agree, the drops always turn colour on the top bit of water b4 u shake it > anway. and then changes all of the water colour when u shake it [quoted text clipped - 39 lines] >>> >>>Thx in advance for any help. The LFS is an idiot. Shake it. Their is NO WAY the chemist that designed the test can predict how the drop is going to fall in just the right way to react with just enough water in the test tube to react by changing colour in only the top portion. Add one drop, shake, another, shake, etc, until the colour changes and remains changed. And BTW, I'm a chemist so I know how these tests work. You need a homogenous solution. Robert > Well this might sound like a dump question from the subject but am kind of > confused. [quoted text clipped - 14 lines] > > Thx in advance for any help. On a slightly different subject, when comparing varying colours of the test to a sample colour card, should you hold the test up to the card or slightly away (if so, from what distance) and under what lighting conditions. The instructions are never clear Some test kits have colours that are so close between each value, that 2 people in the same room with the same test would give a different reading. My guess is that you should hold the test directly up against the card in neutral lighting. > Well this might sound like a dump question from the subject but am kind of > confused. [quoted text clipped - 15 lines] > > Thx in advance for any help. Try to do your testing during the daytime, and view your results under indirect sunlight. Or buy 6500K bulbs for your kitchen and look at your kits under that lighting. Marc > On a slightly different subject, when comparing varying colours of the test > to a sample colour card, should you hold the test up to the card or slightly [quoted text clipped - 26 lines] >> >>Thx in advance for any help.  SignaturePersonal Page: http://www.sparklingfloorservice.com/oanda/index.html Business Page: http://www.sparklingfloorservice.com Marine Hobbyist: http://www.melevsreef.com Or use a fine grade white paper for the background and compare the two solution. CapFusion,... > Try to do your testing during the daytime, and view your > results under indirect sunlight. Or buy 6500K bulbs for [quoted text clipped - 38 lines] > Business Page: http://www.sparklingfloorservice.com > Marine Hobbyist: http://www.melevsreef.com |
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