Demonstration of orange II

Chemicals needed

distilled water

2-naphthol GSGESUND.gif (476 Byte) Xn  GSUMWELT.gif (758 Byte) N    R 20/22-50     S (2)-24/25-61

sodium nitrite solution, dilutedGSGESUND.gif (476 Byte) Xn GSUMWELT.gif (758 Byte) N    R 8-25-50    S (1/2)-45-61

sulfanilic acid GSGESUND.gif (476 Byte) Xi     R 36/38-43    S (2)-24-37

Equipment needed

test tube

Test procedure


The mixture can be disposed of as halogen-free organic waste.


This experiment corresponds to the usual procedure for the demonstration of azo dyes. Orange II has the following structure:

orange2.gif (2001 Byte)

Orange II - 4-[(2-Hydroxy-1-naphtyl)azo]-benzenesulfonic acid monosodium salt


DSCN0285.JPG (197195 Byte)   orange2_2.jpg (8398 Byte)

With neutral conditions the coloration develops in the course of several minutes

orange2_3.jpg (8812 Byte)   orange2_4.jpg (8544 Byte)


based on experiment 2058 S "Orange II", S. 334, [2]