Division 4.3.1

Dissolve 0,5 g of disodiumphenylphosphate (Na2C6H5PO4.2H2O) in 4,5 ml of Solution B (4.2). Add 2 drops of Solution E (4.5) and allow to stand 30 minutes. Extract the colour with 2,5 ml butanol (4.10). If necessary, repeat the colour extraction. After separation, discard the butanol. This solution can be kept for several days in a refrigerator. Develop and extract the colour once more before use.