Tested Overhead Projection Series Compiled by
HUBERT N. ALYEA Princeton University
18. THE PHOSPHORUS FAMILY
C. Arsenic (continued) Dem. 541-Marsh
Tesl for Arsenic
Experiment developed by Charles Owens. To show: Marsh test for arsenic. Note: antimony will be used since it is less poisonous. Materials: A 4-mm glass tubing 20 cm long attached to the rubber tubing of G-4; mossy zinc in t,he generating chamber and 6 N HC1 in t,he ot,her chamber; SbC1,-aq. Procedure: Put half a dropperful of SbC13-aqin (G-4). Project,. Open the valve so that the HCl runs into the Zn, and Hz is generated. Wait 30 seconds to expel air, then light the Hz as it issues from the glass tubing, held horizontally. Now bring a lighted alcohol burner under the midsection of the tubing. Observations: The Sb imparts a ghast,ly greenish color to the invisible hydrogen flame. SbH3 forms; the burner heat dissociates it to form a silvery antimony mirror in the tube. Reactions:
glass, horizontal stage). (f) I n H-3 stir 0.5 ml of the mixture with 5 ml of trichloroethane: the iodine dissolves to form a red solution as in (a). (y) Filter: the Sb is caught on the filter paper. Compound, SbIl: (h) I n H-3 gently heat 0.5 ml of the mixture with 5 ml tri-chloroethaue: yellow SbIs forms. (i) Cool by plunging the culture tube into icewater (in H-3): red crystals of Sb13form (show macm). ( j ) Reheat in H-3; the red crystals dissolve, reforming the yellow modification of ShI,. (Ic) Show that the red crystals have a definite melting point, much lower than that of Sb in (d). 2 Sb
- -
+ 3 4 in solution warm 2 S b 4
oald
yellow
2 Sb4 red
A. J. CHEM.EDUC.,20, 40 SCATTERGOOD,
Reference: (1943).
Dam. 543-Antimony
Sulfides
Sb& precipitate and colloidal sol.
To shous:
Procedure and Observations: Same as Dem. 538, hut substituting SbCI3for AsCla. Dem. 544-Thio-antimonates
To show: Separation of arsenic group from copper group in routine cation analysis. Procedure and Observations: Same as Dem. 539, but substitute SbC1,-aq for AsCla-aq, and Cd+2 for C U + ~ . Dem. 545-Hydrolysis
of SbCla
To show: Formation of SbOC1.
D. Antimony Dem. 542-Antimony
Materials: droppers. plus Iodine
Procedure: Project C-3 with each cell one-fifth full of a clear solution of ShC5 (e.g., Sb203 conc. HCI). To cells 2 and 3 add water sufiicieut to precipitate white SbOC1. Then add to cell 3 sufficient HCI-conc. to give a clear solution.
+
Experiment developed by Kenneth Jackman. To show: Elements, mixtures, compounds. Materials: Iodine, tri- or tetra-chloroethane, powdered and crystalline antimony, funnel and filter paper, tongs, Bunsen burner, small test-tube, watchglass, stirrer, mortar and pestle, cell H-3, test tube holder. Procedure and Results: Iodine: (a) I n H-3 stir 5 ml trichloroethane plus a tiny crystal of 12: a deep red solution forms. (b) Evaporate a concentrated solution on a watchglass, horizontal stage: crystals of Iz re-appear. Antimony: (c) In H-3 stir 1 ml crystalline Sb with 5 ml trichloroethane: Sb is insoluble and settles out. ((1) Over a Bunsen flame, in a small test tube, heat intensely lg. powdered Sb. Project the flow of molten Sb, solidifying rapidly upon cooling.
+
SbCIa-aq, conc. HC1, Cell C-3, medicirre
+
Mixture, S b I,: (e) Grind 2 ml crystalline Sb 1 ml II (macro) pointing out that excessive grinding would make the mixture appear homogeneous (watch-
Reactions:
+
SbCls H20 e SbOCll clear whik
+ 2 HCI
A reversible reaction is involved, being driven to the left by the addition of HCl, and to the right by the addition of HzO.
E. Bismuth Dem. 546-Diamagnetism
of Bismuth
Experiment developed by Charles Owens. To show: Influence of a magnetic field on a cryst,al of bismut,h. Volume 45, Number 10, October 1968
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