Verification of copper and cadmium with dithizone

Chemicals needed

distilled water

cadmium nitrate O T    R 8-23/25-33-40    S (1/2)-22-45

diethyl ether  F+      R 12-19-22-66-67     S (2)-9-16-29-33

ethanol dithizone solution   F   R 11    S (2)-7-16

copper(II)-chloride (anhydrous or dihydrate) T     R 25-36/37/38    S 37-45

One can also use copper(II) nitrate and/or cadmium chloride.

Equipment needed

3 test tubes

test procedure

• Ventilation or exhaust hood! Extinquish all fires! Avoid contact with the reaction solutions, take precautions for the removal of spilled salts!
• One puts in one test tube a very small spatula-tipful of copper salt, in another cadium salt(caution!).
• Now one puts into each test tube about 1 ml of water and adds a drop of ethanol dithizone solution to each.
• One adds to each of the three solutions about 0.5 ml of diethyl ether and sways vigorously (caution!).
• The ether-like layer (epiphase) has now taken on a characteristic coloring: blue (distilled water), green-yellow (copper), pinkt (cadmium) respectively.
• If desired one can combine the copper- and the cadium-bearing solutions together. One sees then the coloring which arises when both are simultaneously present (brown).

Disposal

• Both metalliferous solutions one disposes of as heavy metal waste, the blank test can be deposited into the drainage.

Elucidation

The uncomplexed colored dithizone forms with CU(II) and CD(II) hydrophobic characteristically colored complexes.

cadmium dithizonate

Photos

from left to right: blank test, copper(II), cadmium(II)

Literature

derived from 5.2. Experiment 1, "Arbeitsgang für den Nachweis von Kupfer- und Cadmiumionen nebeneinander", p. 67, [6]