LaMotte HYDROPONICS TEST KIT HP-1 - Manual (Page 4)

PO TAS SIUM
A turbidimetric method is used for the determination of potassium in the
nutrient solution. It is suggested that the nutrient solution be diluted to a
1 to 5 ratio with deionized water to bring the sample concentration within
the range of the test. A 1 to 5 dilution involves diluting 2 mL of the
sample to 10 mL with deionized water.
1.
Remove the square inner tube and collar from the double tube
(0780).
2. Fill the round tube to the first line (8 mL) with nutrient sample.
3. Fill to the second line (16 mL total) with deionized water.
4. Add 2 drops of *Sodium Hydroxide Reagent (4259). Cap and mix.
5. Use the 0.5 g spoon (0696) to add one level measure of
Tetraphenylboron Powder (6364). Cap and shake vigorously until all
the powder has dissolved. A white precipitate will form immediately.
Wait 5 minutes.
6. Shake the tube again. Remove cap and slowly insert the square tube
with the collar. The square tube will slide up and down through the
collar and fill with liquid.
7. Viewing from above, adjust the square tube into the turbid solution
until the black dot on its base is obscured. Hold the round tube at the
top to avoid blocking light.
Record the height of the liquid in the square tube on the scale.
Calibrations represent parts per million potassium. If the original
sample has been diluted 1 to 5, the reading should be multiplied by 5
to obtain the potassium content of the original sample.
NOTE:
Brush tubes thoroughly after each use.
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