Qualitative analysis for nickel. Dem. 657 - Journal of Chemical

Qualitative analysis for nickel. Dem. 657. Hubert N. Alyea. J. Chem. Educ. , 1969, 46 (8), p A537. DOI: 10.1021/ed046pA537.7. Publication Date: August...
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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