Once the salt is dissolved in the sample of distilled water, return the mixture to the one litre bottle, re-seal the bottle, shake and then re-open.
The next step is to withdraw exactly 2 ml of the water and add it to the second 1liter bottle of distilled water. Seal and shake the bottle. When well shaken, open and immerse a nitrite dipstick into the liquid. Wait 30 seconds and then read from the colour chart the concentration of nitrite in the second water bottle. If the original 5gm sample is pure, the expected colour change that matches 10 mg/ litre will be seen. If lower concentrations are noticed it is likely the original sample of nitrite is not 100% pure.
Reading a nitrite test strip to confirm sample purity
The kits contain: digital scales (for accurately weighing out the 5gm of powder for testing), a 2ml disposable pipette (for the accurate measurement of the volume of distilled water to be withdrawn from the bottle), several dipstick nitrite test strips and a colour chart (for reading the results).