Tested Overhead Proiection Series Compiled by
HUBERT N. ALYEA Princeton University
21.
METALS OF GROUPS IV-VIII
E. Group VIII. (Fe, CO, Ni) Dem. 6 5 1-Qualitative
continued
Analysis for Iran
To show: Steps in the routine analysis for Fe. Materials: C-3, FeCb-aq, NHaOH, KCNS-aq, HCIaq. Procedure: Project C-3 with cells three-quarters full plus a dropperful of FeC1,-aq. (a) Add a few drops of NHlOH to each. (b) Add HCI-dil to cells 2 and 3. (c) Add a few drops of KCNS-aq to cell 3: Observations: Fe+++-+ Fe(OH)a 4 yellow red ppt
-+
Fe+++ yellow
-
FeCNS++ red
Note: It is instructive to dilute 1 M FeC13 successively and then test with KCNS to observe the extreme sensitivity of this test.
Dem. 652-Coboltous
Hydroxide
Experiment developed by Alphonse Palermo. To show: Formation of cobaltous hydroxide. Materials: CoCL-aq, clear limewater, C-1, diagonal dropper block SD-22 (Dem. 133). Procedure: Project C1 three-quarters full of water, with droppers in SD-22 containing CoC1,-aq and clear Ca(OH), respectively. Allow the reagents to mingle under water. Observations: Blue CO(OH)~ precipitates.
Dem. 653-Cobalt
To show:
Camplexes with NHs-aq
Dem. 654--Cobalt Complexes with HCI
To show:
Formation of complexes.
Materials: stirrer.
12 M HCl, conc. NHa-aq, 2 M CoCl,, C-4,
Procedure: Mix the HC1 and CoClz in cells in G4 as follows: add 1dropper full of CoCL soh. to each cell. To cell I add 30 drops 12 M HCI, to cell 2 add 20 drops HC1 and to cell S add 10 drops HCI. Insert plastic bars to reduce length of light path. Note various colors of chloride complexes. Observations: Variations from blue, violet, and pink represent degrees of displacement of H 2 0 by C1- in the coordination sphere of Co++.
Dem. 655-Cobalt
Complexes with C2H60H
To show: Formation of complexes. 2 M CoC12, 95% C2H60H,C-4, stirrer.
Materials:
Procedure: Fill cell 1 three-quarters full of GH50H, cell 8 half-full, and cell S one-quarter full. Add a dropperful of CoCL-aq to each. Project. Stir. Observations: Colors varying from blue, violet and pink are formed as cobaltous ion coordinates with 3, 2, or 1 molecules of alcohol, replacing the water which was originally in the coordination positions.
Dem. 656-Ni++
plus Co++
To show: A colorless mixture resulting from mixing nickelous with cobaltous ions. Materials:
C 3 , NiChaq, CoC1,-aq. Procedure: Project C-3 nearly full of Co+%in cell 1 and Ni+2 in cell 3. Transfer equal volumes of Co+= and Ni+2 into cell 2. Observations:
A colorless mixture results.
Formation of complexes.
Materials: 2 M CoC12, conc. NH,-aq, C 4 , stirrer. Procedure: Mix the CoCI, with NH3-aq in C-4 as follows. Add 2 drops CoCl2 to each cell. Add 5 drops NH3 to cell 1 , 3 drops NH3 to cell 2, and 1 drop NH3 to cell 5. Add about 3 ml H20 to all cells, insert plastic bar and note colors and precipitates. Observations: Cell 1 is a solution of the green ammonia complex. Cells 2 and S contain varying degrees of ammonia coordination and cobalt hydroxide. Reference: SIDGWICK, N. v., Chemical Elements and Their Compounds, 1950, page 1385, 1390-2.
Dem. 657-Qualitafive
To show:
Analysis for Nickel
Steps in the routine analysis for Ni.
Materials:
C-3, NiClzaq, NH40H, NazS, NaOH.
Procedure: Project C-3 three-quarters full of water plus a dropperful of NiCkaq. (a) To cell 1 add NHIOH in increasing amounts. (b) To cell 2 add N&S-aq. (c) To cell 3 add NaOH.
-
Obserualions:
(b) Ni++ pea-green.
-
(a) Ni+% NiS
4
-
Ni(OH)Z PPt (grey). (c) Ni++
Ni(NH&+%. Ni(OH)% 4
Volume 46, Number 8, August 1969
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A537
