Cocktail 'Old Nassau' - Modified Landolt Reaction

Demonstration Experiment on Video

Cocktail 'Old Nassau' - Modified Landolt Reaction

Objective: Reaction Rate

Peter Keusch

German version

Chemicals:
sodium disulfite
potassium iodate
mercury(II) chloride
starch, soluble

Glass wares:
conical measure, graduated, 500 mL
2 measuring cylinders 500 mL
3 volumetric flasks 1000 mL
3 beakers 50 mL
3 beakers 200 mL
beaker 500 mL
volumetric pipette 25 mL
3 volumetric pipettes 50 mL
4 pipet bulbs

Hazards and safety precautions:

Sodium disulfite may cause irritation and may be harmful if swallowed. May cause allergic reaction.skin and eye irritant.

Potassium iodate is harmful if swallowed. May be harmful by inhalation or through skin absorption. Irritant.

Mercury(II) chloride is a poison. May be fatal if swallowed or inhaled. Chronic exposure may lead to systemic effects and build-up of mercury in the brain, liver and kidneys. May cause memory loss, tremors and other serious effects.

Safety goggles and protective gloves must be worn. Suitable ventilation!

Preparation of the solutions:

Solution A: A paste 0.4 g of starch with a few mL of deionized water is made. 500 mL of boiling water are poured onto the paste while stirring. When the solution is cooled down to room temperature 13.7 g of sodium metabisulfite are added. The mixture is poured into a 1000 mL volumetric flask which is made up to the mark with deionized water.

Solution B: A 1000 mL volumetric flask containing 3 g of mercury(II) chloride is made up to the mark with deionized water.

Solution C: Another 1000 mL volumetric flask containing 15 g of potassium iodate is also made up to the mark with deionized water.

Using 3 beakers 150 mL of solution A, 175 mL of solution B and 150 mL of solution C are prepared.

Experimental procedure:

The three solutions above are poured in alphabetical order A, B, C into a 500 mL conical measure.

Results:

After about two seconds an opaque orange color precipitate is formed. After further two seconds the mixture turns blue-black.

Videoclip (Download RealPlayer .rm file)<

Hubert N. Alyea (1903 - 1996)
http://alumni.princeton.edu/~ptoniana/alyea.asp
".... while the Tiger stands defender of the Orange and the Black"
Like many other classic chemistry experiments, the 'Old Nassau' experiment has it roots with the grand master of lecture demonstrations professor Hubert N. Alyea. Alyea accompanied the presentation of this experiment in lectures with the song 'The Orange and the Black', an ode upon the two tigers, flanking Nassau Hall's entrance at the Princeton University (New Jersey):

''Although Yale has always favored
The violet's dark hue,
And the many sons of Harvard
To the crimson rose are true,
We will own the lilies slender,
Nor honor shall they lack,
While the tiger stands defender
Of the Orange and the Black.''

written in the late 1880s by Clarence Mitchell 1889

Alyea demonstrates the 'Old Nassau Reaction'. (Download RealPlayer .rm file)

Discussion:

In addition to the reaction steps described under Landolt Reaction - Iodine Clock Reaction a further reaction takes place. Mercury(II) ions react with iodide ions to form an orange color precipitate of mercury(II) iodide, as soon as the iodide ion concentration is large enough ( ion product > solubility product of HgI₂ ). Using the concentrations specified above, mercury iodide precipitate does not dissolve. The orange suspension of the HgI₂ precipitate is masked by the deep-blue-black iodine-starch-complex when HSO₃^- ions are consumed up.

References:
Old Nassau - Haloween Reaction
Demonstration Experiment on Video Landolt Reaction - Iodine Clock Kinetics
Demonstration Experiment on Video 'One Cola and one Beer, please' - Modified Landolt Reaction

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