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Re: [APD] Pottasium Testing

rlxdn10sity at aol_com wrote:
> I recently purchased a Lamotte Potassium test kit. The directions are somewhat ambiguous. It says to add reagent and then insert tube until black dot at bottom becomes obscure. I?m not sure if the tube I received is defective but there is a significant portion of the bottom of this tube that is black and though its visisbility fades the further into the test solution I insert it, it never dissapears. I know this could mean that I?m that low on Potassium, but if I were?nt, I?m not sure at what point the visibility of the black dot would be considered obscure. It seems the term obscure is left open to the interpretation of each individual. Does anyone have experience with this kit? Any suggestions or tips? I may call Lamotte and ask them but I thought to try you guys first. Thanks for your help. Chas.

Whenever I am in doubt about a test kit, I try to measure a reference. 
With potassium it's easy. Just add a known amount to a volume of water 
and test it. It's easier for larger quantities. For instance, I would 
add 10g of KCl to 1,049mL of deionized water. Now, you have 5g/L of K. 
For every mL of that solution you add to a clean liter of deionized 
water, you get 5mg/L K. Add enough to give you 10, 15, 20, or whatever 
you want to test with.

Jerry Baker
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