Tested Overhead Proiecfion Series Compiled by HUBERT N. ALYEA
Princeton University
5. STATES OF MATTER
10 mm plastic dishes. Mother liquor containing 5 g 5 g CuSOn.5HzO potash alum (KAl(SO&.12HzO) 30 ml water.
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D. Solid State 2. CRYSTALLIZATION Dem. 284--Wrifing w i t h Alum Cryrtoh
Experiment developed by Charles Owens To show: Growth of alum crystals along a streak of alum. Materials: microscope slide 3 X 1 in., potassium aluminum sulfate crystal, saturated potash alum solution. (IiAI(S04)2.1 2 8 0 ) Procedure: Write TOPS on the microscope slide using the alum crystal as a pencil. Project H-3 with a culture tube half-full of saturated a h m solution. Drop the slide into the solution. Observations: The word TOPS appears on the screen as the alum writing "seeds" the saturated solution, and crystals grow along the writing. Reference: (1934).
WAILES,R. B., J . Chem. Educ., 11, 189
Dem. 285-Rate
of Ctytallization and Cryrtol Size
To show: The slower the rate of crystallization, the larger the crystals formed.
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Procedure: (a) Dry the following overnight at room temperature and about 50% humidity (1) 3 drops of solution on a microscope slide (2) a solution 3 mm deep in the plastic dish, and (3) ditto, 10 mm deep. (b) Test for purity of alum crystals. Removealum crystals which have formed overnight, flush them thoroughly with distilled water to remove all mother liquor, and place about 1 g of them in cell 3 of C-3. Put one drop of 111 CuS04 in cell 2. Put 10 ml distilled wat.er in each of the three cells of C-3. Project. Now add 2 drops of potassium ferrocyanide solution to each. Stir. Observafions: (a) In all cases crystals of blue vitriol CuS04,5H20form first, and subsequently clear, colorless alum crystals form and cover them like snow covering a range of mountains. (b) Cells 1 and 3 are strawcolored, but in cell 2 an opaque, yellow-brown precipitate of cupric ferncyanide forms. This shows that there was no Cu++ in the alum crystals. Reference: (1032).
STONE,C. H., J. Chem. Educ., 9, 1107
Dem. 287-Growing
Experiment developed by Evangeline B. Klug
20 ml H,O. (b): Materials: (a) 3..5 g (NH&HPO, 3.5 g tartaric acid CnH406.H20 20 ml HzO. (c): 17.2 g hlgClp 30 g H20. (d) : 1vol cone. SH3-aq 5 vols. H20. 260 ml beaker, H 3.
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Procedure: (Macro)-in a beaker mix a b and stir, then c and stir, and finally enough d to redissolve any precipitate which forms. Then add 2 ml d in excess, stirring gently to mix. Threoquartew fill t,hree culture tubes with this solution. Tube 1: place in H-3 and project. Tube 2: shake gently for 15 see, t,hen project. Tube 3: shake vigorously for 1 min, then project. Observations: Tube 1 crystallizes very slowly, forming coarse crystals; tube 2 forms smaller crystals; tube 3 forms very fine crystals, immediately. Reference: DUNNING, J., PRATT,P., and LOWMAN, 0. E., J . Chem. Educ., 11, 624 (1934). Dem. 286-Purification by CtytaIIizotion Experiment developed by Lucian J. TVnukmcski.
To show: Pure crystals of alum grown from alum solution contaminated with cupric sulfate. Materials: Cell C-3, stirrer, 1 RI potassium ferricyanide I
