Solubilities of iodine. Dem. 623


water and shake. Using a hypodermic needle, inject carbon tetrachloride into the middle of the water layer. Observations: (a) Iodine is not very solub...
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4. OTHER OXY-SALTS

Dem. 6 18-Decomposition

To show:

of KCIO,

Thermal, catalyzed, decomposition.

Procedure: Project G-1, heating '/lo a tubeful of IiC103 until gas evolves. Dump in a pinch of A!InOl. Show test macro with a glowing splint.

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30%. The MnO, Observations: 2 RC103 -t 2 IiCI accelerates decomposition. The splint bursts into flames. Dem. 6 19-Catalytic

Decomposition of Chlorotes

tubes 1 and 8 are exposed. Finally remove the cardboard altogether. Observation: The solutions bleach. Note: Benzene can be used (forms hexabromobenzene) but is not as satisfactory.

E. Iodine Dem. 622-Tincture

Demonstration: Experiment developed by Raymond P. Garman.

To show: Oxide catalysis of chlorate decomposition.

To show:

Materials: (a) chlorates, IiC108, ;\!Ig(C10a)2. (b) Catalysts: Cr203, Whol, k.e30a, NiO, CuO, Pz03 As203. (c) Inerts: MgO, CaO, BaO, ZnO, Si02, BilO3. Cell H-3, splints, burner. DANGER: DO not use silver, lead, or ammonium salts.

Materials:

Procedure: Fill the two culture tubes of H-3 full of IIClO,. Project. Heat each cell equally until the RCIOa melts and bubbling occurs. Blow out the alcohol lamps, wait 10 sec for bubbling to cease, then drop in, simultaneously, a grain of oxide into each (see list above). Note which begins to bubble and evolve gas again, at this lower temperature. Remove H-3 and test (macro) by lowering a glowing splint into the gas in each tube to test for 02. (CARE: DO not lower into molten chlorate). Try all chlorates. Tabulate results. Observations: The oxides listed above as catalysts are effective on all three chlorates. References: MSEH, M., J.. CHEM. EDUC., 17, 494 (1940); CAMPBELL, J. A,, ibid., 23, 582 (1946); STANDEN, A,, ibid., 24,201 (1947).

D. Bromine Dem. 620-Bromine

Bleaching Indigo

To shotu: Bleaching with either Br2or Clz. Materials: Indigo-aq, NaOH-aq, Brz-aq, C1,-aq, test tubes, C-3.

of Iodine

Formation of tincture of iodine

It, ethanol, H-3.

Procedure: Project a culture tube in H-3. Drop in a few flakes of solid iodine. Now pour in 10 ml of ethanol. Let stand. Observations: The iodine can be seen diffusing into the ethanol to form a dark reddish-brown tincture. Dem. 623-Solubilities

To shotu:

of Iodine

The relative solubilities of iodine.

Materials: Iodine, benzene, carbon tetrachloride, IiIaq, cell C-3, test tubes. Procedure: (a) Shake large crystals of iodine with tubes half-full of water, and of IiI-aq respectively. Project immersed in water in C-3. (b) Shake large crystals of iodine with tubes half full of ICI-aq, alcohol, benzene. (c) Dissolve crystals of iodine in benzene. Quarterfill a test tube with the solution, add a quarterful of water and shake. Using a hypodermic needle, inject carbon tetrachloride into the middle of the water layer. Observations: (a) Iodine is not very soluble in water, but forms a dark solution (IiI,) with IiI-aq. (b) The darkness of the solutions shows the relative solubilities is alcohol > benzene > IiI-aq. (c) Three layers form, showing the relative solubilities in benzene (brown), water (very light brown), and carbon tetrachloride (violet). Dem. 624-Iodine

and Turpentine

Experiment developed by Raymond P. Carman.

Procedure: Half-fill the test tubes with pale blue indigo solution, and project in water in C-3. Add 2 ml of Br,-aq to cell 1, 2 rnl of Br2-aq 1 ml of NaOH-aq to cell 8, and of CIS-aqto cell S. Stir.

CloHls 812 excess iodine).

Observations: Cell 1 turns yellowish, and cells 8 and S become colorless.

Materials: Iodine, turpentine, 100 ml beaker, hot,plate, medicine dropper, H-3.

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Dem. 6 2 I-Photo-bmminotion

To show: The photo-hromination of toluene. Materials: Bromine, toluene, C-2, 3 test tubes, 6-in. square of cardboard. Pvocedure: (a) Add a few drops of bromine to 30 ml of toluene to give a deep red solution. Place in 3 test tubes immersed in water in C-3 on the projector stage (lamp off). Shielding tubes 8 and S fron the lamp by interposing the cardboard, turn on the projector. At the end of 2 min, shift the cardboard so that both

To show:

+

Turpentine oxidized by iodine. -t

10C

+ 16HI (heat vaporizes some

Procedure: (CARE: keep hand away from mouth of tube). Project two flakes of iodine in a culture tube in H-3. Heat to give warm I? vapor. Meanwhile heat 10 ml turpentine in a beaker on a hot-plate. Using medicine dropper to beep hand away from mouth of tube (CARE) allow a few drops of hot turpent,ine to drop into the warm 1%. Observations: Violent eruption, violet turbulenrc. Reference: ARENSON, S. B. for CLARK, J. D., J. CHEII. EDUC.,17,468 (1940).