OXIDATION OF BROMIDE AND IODIDE IONS
Submitted by: Ii. R. Dutton, Michigan State University, East Lansing Checked by: Georgc Ferris, Haslett High School, Haslett, Michigan PREPARATION
Prepare an acidified 0.01 M solution of potassiunl iodide and potassium bromide by adding 0.17g ICI and 0.12g KRr to .5 ml concentrated HCI in 95 ml HzO. Saturate 100 ml water with chlorine. Provide a flask or large test tube, stopper, and some carbon tetrachloride.
and obsen,~successive color changes; purple (iodine) black (iodine plus bromine), brown (iodate, colorless, plus bromine), yellow (an interhalogen compound ot Rr and CI- plus CL). REMARKS
Ask the class to explain thc color changes and to compare with standard emf potentials.
DEMONSTRATION
14ace the halide solution and 10 ml of carbon tetrachloride in the flask, add a few drops of Clz water, shake, and observe the purple color of iodine in the CCII. Slowly add more Clz water, shaking between additions,
These reactions have been used to test for Br- in the presence of I-. The process may he repeated with each halide ion separately if desired.
DEMONSTRATION NOTES From time to time items such as the following, which do not require a jXl half-page, will be listed together. Some of them will be modifications oj preoiously published demonstrations, i n which case it i s suggested that the?/ be clipped and attached to the pertinent experiment. CORRECTION
On the December, 1962 Tested Demonstration page we misspelled the name and address of the first tolltributor. I t should have been H. R. Tietze of Kewcastle University College, iYew South Wales, Australia. We extend our apology. HYDROGEN PEROXIDE
Robert H. Long of Green Mountain College, Poultney, Vt., suggests demonstrating the oxidizing action of hydrogen peroxide by adding 2 or 3 ml of a 3% solution to a solution of copper (I) chloride made by dissolving 05 g copper (I) oxide in 2 ml concentrated HCI and diluting with 10 ml H20. The development of the blue
hydrated Cu (11) + + ion indicates the oxidation of Cu (I) to Cu (11). EDITOR'SXOTE:Adding H202to a dilute acidified solution of KMnOn will show the reducing properties. HELP WANTED
Several demonstrations on chromatography and on electrolysis have been received from time to time which are too long for our format or are overlapping in content. We propose to submit these to a panel to develop the best composites possible. Please send us your favorite dcmonstration on these topics. All contributions will be acknowledged. Address contributions to Prof. Frederic B. Dutton, Science and Mathematics Teaching Center, Michigan Stat? University, East Lansing, Mich.
Journal of Chemieol E d u c d i i i
.
Morch 1963
