Nickel(II) reacts with dimethylglyoxime [C4H6(NOH)2] to form a coordination complex. The formation of the red chelate occurs quantitatively in an aqueous solution at pH 5 to 9. Usually, citric acid is added to lower the interference of iron

1. SHREE MALLIKARJUN COLLEGE SYBSC
SAFETY: Refer to MSDS of nickel nitrate, nickel chloride, dimethylglyoxime, citric acid, ethanol
-Dr. Mithil S. Fal Desai
Aim: Estimate the amount of Nickel present in a given solution as
bis(dimethylglyoximato)nickel(II) in a given solution gravimetrically by counterpoise filter paper.
Chemicals: Nickel salt (nickel nitrate, nickel chloride), dimethylglyoxime, citric acid, ethanol.
Apparatus: Beaker, conical flask, funnel, Whatman 41, glass rod with policemen, water bath,
oven.
Theory: Nickel(II) reacts with dimethylglyoxime [C4H6(NOH)2] to form a coordination complex.
The formation of the red chelate occurs quantitatively in an aqueous solution at pH 5 to 9.
Usually, citric acid is added to lower the interference of iron.
Reaction is as follows:
Ni2+
(aq] + 2C4H8N2O2(aq]  [Ni(C4H7N2O2)2](s] + 2H+
(aq]
To get better result G4 crucible shall be used.
Procedure:
1) Pipette out 25mL of nickel solution in a 100mL beaker and add 5 mL of 0.5% citric acid
solution and stir.
2) Add 25 mL of 1% dimethylgloxime solution to the beaker (red colour precipitate is formed)
and keep the beaker on a water bath for 30 min.
3) After 30 min, cool the solution and add 1-2 mL of DMG solution along the sides of the beaker
and check for complete precipitation.
4) Take 2 filter papers having the same weight and place it in a funnel. (If the weight of the two
filter papers is not equal cut the top edge of filter paper to adjust the weight.)
5) Transfer the precipitate in filter paper and wash the precipitate with 20 mL of water. Finally,
add 5-10 mL of alcohol to remove the excess of water.
6) Keep the funnel along with filter paper in the oven at 60-700C for around 45 min.
7) After 45 min, cool the filter papers in a desiccator and then weigh both the filter papers with
(W1) and without precipitate (W2). (To get constant weights to repeat the step 6 and 7)
8) The difference in weight quantitatively corresponds to Ni-dmg complex formed.
Observation
Table 1.
Constant
weight of filter
paper without
precipitate
“W1’ (g)
Constant
weight of filter
paper with
precipitate
“W2’ (g)
Weight of
Ni-complex
‘A’=W2 – W1
(g)
Molecular
weight of
Complex
‘B’ (g)
Atomic weight
Ni ‘C’(g)
Amount of Ni
in 25 mL
‘x' = A* C/B
(g)
58.71
Result: Amount of nickel in 500 mL is ______g.