Tested Overhead Projection Series Compiled by HUBERT N. ALYEA
Princeton University
Dem. 709-Woier
23. COLLOIDS
Experiment developed by Raymond T . Byrne, Buffalo,
D. Emulsions
1960.
T o show: 1. FORMATION (continued)
Dem. 706-Emulsion
Alcohol
+ Rosin + Hz0
Materials: Ethanol, rosin, H-3, stoppers. Procedure: Project two culture tubes containing 10 ml ethanol. Into tube 2 put a pinch of rosin, then shake to dissolve. Now add 10 ml H 2 0 to each tube, stopper, and shake both together for 10 sec. Let stand. Exhibit macro. Observations: I n tube I the alcohol and water are completely miscible. The solution in tube 2 is opaque, as a permanent emulsion of rosin-coated alcohol suspended in water.
Dem. 707-FfOH
+ H20+ Phenolphiholein
Formation of a water-alcohol emulsion.
Materials: C-3, dil. NaOH-aq, 1%phenolphthalein in EtOH. Procedure: Project C-3 with cells one-quarter full of water. Add drops of NaOH to cells 1 and 2. Now pour half a test-tubeful of the phenolphthalein-alcohol solution into cells 2 and 5, and 1 drop into cell 1. Obseruations: Cell I remains clear red; cells B and 5 turn opaque as emulsions form; The phenolphthalein covers the droplets of alcohol holding them suspended in the water.
Dem. 708-Oil
Emulsion formation.
Materials: Oleic acid, kerosene, 1.5 M NHpOH, two culture tubes, C-3.
T o show: An alcohol-in-water emulsion with rosin as the emulsifying agent.
T o show:
+ Kerosene + NH40H
+ Woier + Soap
Procedure: ( a ) Project tubes, containing 2 ml oleic acid 12 ml kerosene. Shake; let stand. (b) Add 2 ml dil NH40H to one. Shake. Exhibit macro.
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Observations: ( a ) Two clear layers. (b) The ammonia-oleic acid emulsifies the mixture, coating the drops of kerosene suspended in the water; on the screen the emulsion appears opaque. 2. SURFACE ENERGY EFFECTS Dem. 710--Camphor
+ Alcohol + Oil
Experiment developed by Alphonse Palermo T o show: Surface tension effects in the formation of a n oil-in water emulsion. Materials: Soln A : 5 ml soap aq, 25 ml ethanol, 0.1 g camphor, 3 ml linseed oil. Soln B: same as A without the soap. Methylene blue-aq, C-2. Procedure: Project C-2 with the two cells threequarters full of methylene blue-aq. ( a ) Fill a medicine dropper with solution A, hold its tip below the solution in cell 1 of C-2 and let s o h A flow out. (b) Repeat but this time use S o h B (no soap) in cell 2. Stir. Observations: ( a ) An oil-in-water emulsion forms at the tip of the dropper with turbulence because the camphor and the alcohol lower the surface tension of the oil. (b) Without the soap a similar event occurs but the emulsion is unstable; soap is the emulsifying agent in ( a ) and the oil soon breaks into large globules and floats. Dem. 7 1 1-Alcohol
+ Wafer + Rosin
Experiment developed by A l p h m s e Palermo.
Experiment developed by Charlotte Frick.
T o show: Formation of an oil-in-water emulsion with soap as the emulsifying agent.
T o show: Surface tension effects in the formation of an emulsion.
Materials: Linseed or mineral oil, soap-aq, H-3, stoppers.
0.2 g rosin Materials: Soln A : 50 ml ethanol 0.3 g camphor 1 ml soap-aq. Soln B: Same as A but omittin4 the soap. Methylene blue-aq, C-2.
Procedure: Project two culture tubes containing 10 ml Hz0 10 ml oil. To tube 2 add 1 ml soap-aq. Stopper, then shake both tubes, together, for 10 sec. Let stand.
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Observations: Two layers, oil and water, separate in tube I. In tube 2 a permanent emulsion forms, with oil coated with soap suspended in water.
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Procedure: Project C-2 with the two cells threequarters full of methylene blue-aq. ( a ) In cell 1 immerse a dropper holding Soln A , and let Soln A flow down into cell 1. Stir (b) Repeat using Soln B in cell 2. Obseruations: An alcohol-in-water emulsion forms, with rosin as the emulsifying agent. With soap the Volume 47, Number I , January 1970
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Dem 715-NH4CI Smoke
emulsion is stable; without the soap it is not stable, the alcohol dissolving in the water. J. R., J . Chem. Educ., 12,444 Reference: CALDWELL, (1935).
Materials: NHIOH, conc. HC1, C-3; cotton-tipped swab; dil. NaOH-aq, solid NHrsalt.
E. Gels
Procedure: Put 5 ml water in cell 1 and 5 ml conc. NHIOH in cell 3, leaving cell 2 empty. Proceed to lower swab soaked in conc. HCI into the cells 1, then S. Dem. 712-Acetate
Gel
Experiment developed by Carl J. Mancuso.
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CaTo show: Formation of a gel from ethanol (0.4~)~. Materials: 95% ethanol, saturated Ca(OAc)?, H-3, 5 X 5-in square of asbestos. Procedure: (a) Project three culture tubes in H-3, tube 1 containing 3 ml sat. calcium acetate, tube 2 empty, and tube 3 containing 30 ml 95% ethanol (absolute ethanol does not work, dilute it). Now pour the two solutions simultaneously into tube B. Wait a moment, then invert tube 2 in H-3. (b) Macro: scoop a bit of the gel out of tube 2, squeeze excess alcohol out of it, and place the gel on a square of asbestos; set fire to it. (c) Darken room, wipe excess alcohol off the hands (CARE: if wet will burn the hands), pick up bits of burning gel. Observations: (a) Acetate-alcohol gel forms. (b) The gel burns, and can (c) be picked up while burning moderately hot. Dem. 713-Silicate
Garden with FeC18
Experiment developed by Alphonse Palermo. To show:
The rapid growth of a ferric silicate garden.
Materials: Commercial sodium silicate, FeCl3.6Hz0, C-2.
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Procedure: Project 15 ml HzO 5 ml sodium silicate in the two cells of C-2; stir thoroughly. Now drop a few small crystals of FeCls.HzO into each cell. Observations: Shoots of ferric silicate grow with fascinating rapidity on the screen. Call attention to the growth pattern: the tube of silicate ruptures, and a t that point a new bulbous growth begins.
To show:
Formation of smoke.
Observation: Nothing occurs in 1, but in S white NH4C1 smoke curls up from the swab. This is a test for an ammoNH&+. Confirm by mixing NaOH-aq. nium salt in cell 9,and testing with the HC1 swab.
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Dem. 7 16-Cottrell
Precipitator
To show: Precipitation of smoke with electrostatic precipitation of smoke. Materials: NH40H, HCI conc. HC1, Tesla coil or leak tester, 4 X 1-in. wire gauze, 2-02. wide mouth, square glass bottle, droppers. Procedure: Form NH&l smoke by mixing a few drops of NHnOH with HC1-aq. Insert the wire gauze. Project. Touch the leak tester to the gauze and spark. Observations: The smoke clears up. This is the principle of the Cottrell precipitator.
Dem. 7 17-Protected
Foam: COz
+ Albumin
Experiment developed by Alphmse Palermo. To show: Formation of COz bubbles made stable by egg albumin. Materials: Egg albumin, NaHCOa-aq, very dilute HOAc-aq; C-2, stirrer. Procedure: Project C-3 with 10 ml NaHCOsaq in each. Add a pinch of egg albumin to tube 2 and stir. Now squirt rapidly into each cell a dropperful of very dilute HOAc-aq. Observations: Both foam up, but the foam in cell ?2 is stable and remains permanent; the C02 in i t is coated with egg albumin.
T. H., J. Chem. Educ., 18, Reference: HAZLEHURST, 286 (1941).
F. Smokes, Mists, Foams Dem. 714--1itonium Oxide Smoke
To show: Formation of a smoke by hydrolysis. Materials: 2-02. wide-mouth square glass bottle with 2-hole stopper bearing two plastic tubing: one 1-in. long, the other 1-ft long. Procedure: Project bottle containing 2 ml TiCl4. Blow through long tube. Observations: Hydrolysis occurs, TiOz smoke issues from the short tubing.
Dem. 7 18-Protected
Faom: COz
+ Detergent
Same as Dem. 717, but produce COz by dropping an Alkaseltzer into (a) water (b) water containing a pinch of detergent powder.
Dem. 719-Protected
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Foam: 0% Detergent
Same as Dew. 717, but produce O2 instead of COa, by thrusting a cotton-tipped swab moistened and coated with solid MnOz into (a) 3% HzOz, and (b) 3% HzOZ a pinch of detergent.
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