Tested Overhead Proiection Series Compiled by
HUBERT N. ALYEA Princeton Univertity
same time heat the ZnS. (CARE: when reaction is over loosen stopper, turn off oxygen, then blow out burner flame; if not done in this sequence, liquid may suck back into the reactor.)
C. Reduction of Ore Dem. 4 17-Reduction
of C u 2 0 with Charcoal
Expe~,inienfdeveloped by Crosby U . Rogers. Toshow: lletallurgy of an oxide: reduction by carbon. Materials: Cuprite ore (Cu20), or an oxide of copper; charcoal, 4-in. culture tube, limewater, H-1. Procedure: Thoroughly mix 1 g ore with three times its volume of carbon; place in H-1, project. Lead the delivery tube into the culture tube half-full of clear limewater. Project. Heat the mixture intensely for 5 min. (CARE: At the end of the experiment, before removing t,he burner, loosen the stopper so that liquid will not suck hack into the reactor.) Obseruations: Cop comes off and the limewater turns cloudy. 2Cu20 C + 4Cu COXt ; CO? Ca(OH), + CaCO8 i H20.
+
+
+
+
Note: At the end of the experiment the mixture in the reactor can be "panned" and pa~sedaround the class for inspection for copper flakes. Dem. 4 18-Heating
Zinc Carbonate
Experiment developed by Crosby U . Rogers. T o show: The metallurgy of Zn; decomposil~gthe carbonate. Materials: water.
ZnC03 ore, 4-in. culture tube, H-1, lime-
Procedure: One-fifth fill H-1 tube with finely ground zinc carbonate (ore), lead delivery tube into culture tube half full of clear limewater. Project. Heat. (CARE: at the end of the reaction, before removing burner, loosen stopper to prevent liquid sucking back into the reactor.) Observation: ZnC08- ZnO + CaC03 4 HzO.
+
Dem. 4 19-Zinc
+ C02 t ; CO? + Ca(OH)?
Sulfide Heated in Air
Ezpe~iliientdeveloped by Crosby U . Rogers.
-
Reactions: ( a ) ZnS ( h ) 6502
+ OX Zoo + SO21 + ZKMNOI + 2H3O
-
-
piuk
KBO,
+ ZhInSOd + 2HzS04 colorless
A
(r)
ZnO
+
white
ZnO yellow
Obserualions: Iteaction is so exothermic that the powder glows; the glow projects mell in a darkened room if the lamp is turned off and a mirror placed beh e e n the st,ageand H-1.
D. Refining the Metal Dem. 420--Copper
Refined by Electmplating
T o show: Electrodeposition of pure copper from an impure solution. Materials: CuClp,mud, E-1; electrodes: copper spiral (Q) and No. 28 copper wire (S). Procedure: Project E-1 with copper spiral Q and thin copper wire S immersed in conc. CnCL-aq. Call attention t o the thin mid-section of wire S. h-ow stir in a tiny bit of mud, so the solution is opaque. Turn on current so that Cu wire S is the negative pole; eleet,roplate for 2 min using a 9-volt power source. Pour out the dirty solution and replace with clear water. Again project, calling attention to the diameter of wire S. Obsewatim: The thin wire has grown thick as pure copper has plated out from the dirty solution.
Notes: 1. I n industry plates about 4 f t sq and weighing several hundred pounds are electroplated for about two weeks in this purification process. 9. In place of an all-copper wire oue can use ail insulated Cu mire with 3/& in. of thin P t wire soldered to its free end.
T o show: The metallurgy of a sulfide ore; smelting zinc sulfide in air (oxygen). Materials: ZnS ore, I
