Tested Overhead Proiection Series Compiled by HUBERT N. ALYEA Princeton University

21. METALS OF GROUPS IV-VIII E. Group VIII. (Fe, CO, Ni) continued

Dem. 6 5 1-Qualitative Analysis for Iran

To show: Steps in the routine analysis for Fe.

Materials: C-3, FeCb-aq, NHaOH, KCNS-aq, HCI- aq.

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 -+ Fe+++ - FeCNS++ yellow red ppt yellow red

Note: It is instructive to dilute 1 M FeC13 suc- cessively 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. 654--Cobalt Complexes with HCI

To show: Formation of complexes.

Materials: 12 M HCl, conc. NHa-aq, 2 M CoCl,, C-4, stirrer.

Procedure: Mix the HC1 and CoClz in cells in G4 as follows: add 1 dropper 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 H20 by C1- in the coordination sphere of Co++.

Dem. 655-Cobalt Complexes with C2H60H

To show: Formation of complexes.

Materials: 2 M CoC12, 95% C2H60H, C-4, stirrer.

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. Dem. 653-Cobalt Camplexes with NHs-aq

To show: 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 Analysis for Nickel

To show: 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: (a) Ni+% - Ni(OH)Z - Ni(NH&+%. PPt

(b ) Ni++ - NiS 4 (grey). (c) Ni++ - Ni(OH)% 4 pea-green.

Volume 46, Number 8, August 1969 / A537