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Any green precipitate formation is due to Ni(OH)2 precipitate. (Add more ammonia to make it go away.) Make the ethylene diamine solution fresh if there are crystals present in the solution or if it’s more than a year old. The ethylene diamine will oxidize with time. Test prior to class. Discussion: Ni(H2O)6+2 + 6NH3(aq) - Ni(NH3)6+2 + 6H2O.

The Gravimetric Estimation of Nickel: The nickel is precipitated as nickel dimethyl glyoxime by adding alcoholic solution of dimethyl glyoxime C 4 H 6 (NOH) 2 and then adding a slight excess of aqueous ammonia solution. When the pH is buffered in the range of 5 to 9, the formation of the red chelate occurs quantitatively in a solution. Its abbreviation is dmgH 2 for neutral form, and dmgH for anionic form, where H stands for hydrogen. This colourless solid is the dioxime derivative of the diketone butane-2,3-dione (also known as diacetyl). DmgH 2 is used in the analysis of palladium or nickel. Its coordination complexes are of theoretical interest as models for enzymes and as catalysts. Solutions of the Cl-ion react with Ag + ion to form a white precipitate of AgCl.; Ag + (aq) + Cl-(aq) AgCl(s). When excess Ag + ion is added to solutions of the CoCl 3 6 NH 3 and CoCl 3 5 NH 3 H 2 O complexes, three moles of AgCl are formed for each mole of complex in solution, as might be expected. 25481-21-4 - HTLPAEWBUABNNS-UHFFFAOYSA-L - Nickel(II) EDTA complex - Similar structures search, synonyms, formulas, resource links, and other chemical information. Noble-metal-free g-C3N4/Ni(dmgH)2 composite for efficient photocatalytic hydrogen evolution under visible light irradiation Article in Applied Surface Science 319(1):344-349 November 2014 with.

Dimethylglyoxime is a chemical compound described by the formula CH₃C(NOH)C(NOH)CH₃. Its abbreviation is dmgH₂ for neutral form, and dmgH for anionic form, where H stands for hydrogen. This colourless solid is the dioxime derivative of the diketone butane-2,3-dione (also known as diacetyl). DmgH₂ is used in the analysis of palladium or nickel. Its coordination complexes are of theoretical interest as models for enzymes and as catalysts. Many related ligands can be prepared from other diketones, e.g. benzil.

Preparation[edit]

Dimethylglyoxime can be prepared from butanone first by reaction with ethyl nitrite to give biacetyl monoxime. The second oxime is installed using sodium hydroxylamine monosulfonate:^[1]

Complexes[edit]

Dimethylglyoxime is used to detect and quantify nickel, which forms the bright red complex nickel bis(dimethylglyoximate) (Ni(dmgH)₂). The reaction was discovered by L. A. Chugaev in 1905.^[2]

Cobalt complexes have also received much attention. In chloro(pyridine)cobaloxime^[3] the macrocycle [dmgH]₂²⁻ mimics the macrocyclic ligand found in vitamin B12.

References[edit]

1. ^Semon, W. L.; Damerell, V. R. (1930). 'Dimethylglyoxime'. Organic Syntheses. 10: 22. doi:10.15227/orgsyn.010.0022.CS1 maint: multiple names: authors list (link)
2. ^Lev Tschugaeff (1905). 'Über ein neues, empfindliches Reagens auf Nickel'. Berichte der Deutschen Chemischen Gesellschaft. 38 (3): 2520–2522. doi:10.1002/cber.19050380317.
3. ^Girolami, G. S.; Rauchfuss, T.B.; Angelici, R. J. (1999). Synthesis and Technique in Inorganic Chemistry: A Laboratory Manual (3rd ed.). pp. 213–215.

Nickel(II) hydroxide is the inorganic compound with the formula Ni(OH)₂. It is an apple-green solid that dissolves with decomposition in ammonia and amines and is attacked by acids. It is electroactive, being converted to the Ni(III) oxy-hydroxide, leading to widespread applications in rechargeable batteries.^[4]

Properties[edit]

Nickel(II) hydroxide has two well-characterized polymorphs, α and β. The α structure consists of Ni(OH)₂ layers with intercalated anions or water.^[5][6] The β form adopts a hexagonal close-packed structure of Ni²⁺ and OH⁻ ions.^[5][6] In the presence of water, the α polymorph typically recrystallizes to the β form.^[5][7] In addition to the α and β polymorphs, several γ nickel hydroxides have been described, distinguished by crystal structures with much larger inter-sheet distances.^[5]

The mineral form of Ni(OH)₂, theophrastite, was first identified in the Vermion region of northern Greece, in 1980. It is found naturally as a translucent emerald-green crystal formed in thin sheets near the boundaries of idocrase or chlorite crystals.^[8] A nickel-magnesium variant of the mineral, (Ni,Mg)(OH)₂ had been previously discovered at Hagdale on the island of Unst in Scotland.^[9]

Reactions[edit]

Nickel(II) hydroxide is frequently used in electrical car batteries.^[6] Specifically, Ni(OH)₂ readily oxidizes to nickel oxyhydroxide, NiOOH, in combination with a reduction reaction, often of a metal hydride (reaction 1 and 2).^[10]

Reaction 1 Ni(OH)₂ + OH⁻ → NiO(OH) + H₂O + e⁻

Reaction 2 M + H₂O + e⁻ → MH + OH⁻

Net Reaction (in H₂O)Ni(OH)₂ + M → NiOOH + MH

Of the two polymorphs, α-Ni(OH)₂ has a higher theoretical capacity and thus is generally considered to be preferable in electrochemical applications. However, it transforms to β-Ni(OH)₂ in alkaline solutions, leading to many investigations into the possibility of stabilized α-Ni(OH)₂ electrodes for industrial applications.^[7]

Synthesis[edit]

The synthesis entails treating aqueous solutions of nickel(II) salts with potassium hydroxide.^[11]

Toxicity[edit]

The Ni²⁺ ion is a known carcinogen. Toxicity and related safety concerns have driven research into increasing the energy density of Ni(OH)₂ electrodes, such as the addition of calcium or cobalt hydroxides.^[4]

See also[edit]

References[edit]

1. ^Enoki, Toshiaki; Tsujikawa, Ikuji (1975). 'Magnetic Behaviours of a Random Magnet, Ni_pMg_(1-p)(OH₂)'. Journal of the Physical Society of Japan. 39 (2): 317. doi:10.1143/JPSJ.39.317.
2. ^ ^abZumdahl, Steven S. (2009). Chemical Principles 6th Ed. Houghton Mifflin Company. p. A22. ISBN978-0-618-94690-7.
3. ^ ^abcd'Nickel Hydroxide'. American Elements. Retrieved 2018-08-30.
4. ^ ^abChen, J.; Bradhurst, D.H.; Dou, S.X.; Liu, H.K. (1999). 'Nickel Hydroxide as an Active Material for the Positive Electrode in Rechargeable Alkaline Batteries'. J. Electrochem. Soc. 146 (10): 3606–3612. doi:10.1149/1.1392522.
5. ^ ^abcdOliva, P.; Leonardi, J.; Laurent, J.F. (1982). 'Review of the structure and the electrochemistry of nickel hydroxides and oxy-hydroxides'. Journal of Power Sources. 8 (2): 229–255. doi:10.1016/0378-7753(82)80057-8.
6. ^ ^abcJeevanandam, P.; Koltypin, Y.; Gedanken, A. (2001). 'Synthesis of Nanosized α-Nickel Hydroxide by a Sonochemical Method'. Nano Letters. 1 (5): 263–266. doi:10.1021/nl010003p.
7. ^ ^abShukla, A.K.; Kumar, V.G.; Munichandriah, N. (1994). 'Stabilized α-Ni(OH)₂ as Electrode Material for Alkaline Secondary Cells'. J. Electrochem. Soc. 141 (11): 2956–2959. doi:10.1149/1.2059264.
8. ^Marcopoulos, T.; Economou, M. (1980). 'Theophrastite, Ni(OH)₂, a new mineral from northern Greece'(PDF). American Mineralogist. 66: 1020–1021.
9. ^Livingston, A.; Bish, D. L. (1982). 'On the new mineral theophrastite, a nickel hydroxide, from Unst, Shetland, Scotland'(PDF). Mineralogical Magazine. 46 (338): 1. doi:10.1180/minmag.1982.046.338.01.
10. ^Ovshinsky, S.R.; Fetcenko, M.A.; Ross, J. (1993). 'A nickel metal hydride battery for electric vehicles'. Science. 260 (5105): 176–181. doi:10.1126/science.260.5105.176. PMID17807176.
11. ^Glemser, O. (1963) 'Nickel(II) Hydroxide' in 'Handbook of Preparative Inorganic Chemistry, 2nd ed. G. Brauer (ed.), Academic Press, NY. Vol. 1. p. 1549.

External links[edit]

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