Gh And Kh Testing

[neverquit]

Hello: Ok, first let me say I'm not trying to split hairs on this issue, just want to make sure I'm getting accurate measurements.
I'm using the API Carbonate Hardness (KH) and the General Hardness (GH) test kit.....The problem I have is when doing the test the number of drops of test solution added to the test tube with water determine the KH value. Its says to keep adding the test solution until the water turns "bright yellow."........So, after a few drops the water seems to turn yellow.....So what is bright yellow?....That's pretty subjective. What's bright yellow to me, may not be to you......
The same with the General Hardness test. It says to keep adding test solution until the water turns Green.....
Am I making creating a problem that really isn't a problem?... If someone can help me with this, I'd certainly appreciate it.
 
Thanks
Lloyd 

 

[Byron]

I have this same kit.  I only used the KH once, as I am more involved with GH.  The GH will be a sort of orangish colour, and turn quite a burnt orange just before it turns green.  I have found the change from orange to green to be very obvious.  I will say though that this is with my newer kit (bought over a year ago); the previous one I had was much less obvious; I assumed it was old and the regents might have weakened.  It helps to hold the tube over white and look down vertically through the open tube.
 
One wasy to test these is to test your tap water on its own.  Find out the KH and GH from the water supply people, then test it yourself.  Obviously your results should be very close to their numbers, and this might help you see the colour changes better.
 
Byron.

 

[Essjay]

I've always ignored the 'bright' yellow bit and just rely on the colour change. My KH is 3 degrees; it takes just 3 drops to change colour. The reagents never become concentrated enough to look bright, either the initial blue or the yellow.
And with a GH of 6 degrees, I find the orange/green colours in that test never look strong either. If you remove the lid, place the tube on something white and look down into the tube you will be looking through a greater depth of liquid so the colours are easier to see.

 

[neverquit]

Thanks Bryon: I got a pdf of the city's water chemistry, and did a test of the tap water...Yep, makes me feel a little better...Using that as a reference. Thanks again for your suggestion.
 
essjay: Thanks. And, like you it only took 3 drops to change the color. And, as you said, the more you add of the reagents, it never really turns the sample bright yellow. Even the initial blue is kind of faint. And, yes, I read that on the instructions to hold the sample over some white paper and look down at the sample.
 
Thanks again, I really appreciate it....I just want to do the testing correctly, and you two fixed it for me!......
 
Thanks
Lloyd