(4.2) Precipitate formation: Form precipitate as shown below.
a) Transfer 5 mL - 15 mL (no more than the equivalents of 30 mg as K2O) of the extract to
a 100-mL volumetric flask.
b) Add water to the solution to make about 30 mL.
c) Add about 5 mL of formaldehyde solution and add 5 mL of sodium hydroxide solution
(120 g/L).
d) Add one or two drop (s) of tetraphenylborate solution per second while shaking to mix.
e) Add water up to the marked line and leave at rest for about 10 minutes.
f) Filter with Type 3 filter paper to make the sample solution.