The bulky character of Ni complex limits the mass of nickel that can be handled conveniently and thus the sample mass. Since dimethyglyoxime (DMG) is only slightly soluble in water (0.063 g in 100.0 mL at 25 °C), an alcoholic solution of it is used as the precipitating reagent in the experiment. 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. Many related ligands can be prepared from other diketones, e.g. Dimethylglyoxime can be prepared from butanone first by reaction with ethyl nitrite to give biacetyl monoxime.

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.

Gravimetric Analysis Lab Answers

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]

History Of Gravimetric Analysis

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]

Estimation Of Nickel Using Dmg By Gravimetric Analysis Formula

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.

Estimation Of Nickel Using Dmg By Gravimetric Analysis Example

Procedure:

• The given nickel solution is made up to 100mL in a standard measuring flask.
• 20 mL of solution is pipetted into a 250 mL beaker.
• About 5 mL 1:1 HCl is added and diluted to 150 mL.
• The solution is heated to 70-80째C. 25 mL of 1% dimethyl glyoxime in alcohol is added, immediately followed by dilute ammonia solution drop wise until it strongly smells of ammonia.
• The solution containing the precipitate is heated in a water bath for 30 minutes.
• The precipitate is allowed to stand for an hour.
• Filter the solution through a previously weighed sintered glass crucible.
• The precipitate is washed with cold water to free chloride.
• The crucible is placed in a dry 100 mL beaker and heated in the air oven at 110-120째C for 1 hour.
• It is cooled in a desiccator and weighed. Repeat drying until constant weight is obtained.

Calculation:

Mass of sintered glass crucible = a g.

Mass of sintered glass crucible + nickel complex = b g.

Mass of dimethyl glyoxime nickel complex = (b-a) g.

288.69 of nickel complex contain 58.69 g of nickel.

Mass of nickel in (b-a) g of complex .

Therefore, Mass of nickel in the whole of the given solution .