Division 3.7 Phosphate buffer solution, c = 0,01 mol/l.

Dissolve 1,36 g of KH₂PO₄ (3.1) in 500 ml of water (3.11), add 3,5 ml of orthophosphoric acid (3.2) and 10,0 ml of 6-methyl-2-heptylamine (3.4). Adjust the pH to 4,0 with orthophosphoric acid solution (3.3) and dilute to 1 000 ml with water (3.11).