During a gravimetric determination of nickel ions in a solution, a student precipitates nickel dimethylglyoximate ([Ni(dmg)2][\text{Ni}(\text{dmg})_2][Ni(dmg)2]) and collects it using a pre-weighed sintered glass crucible.
To find the mass of the recovered precipitate, the student:
This method does not give an accurate mass of the precipitate.
Which of the following modifications to this procedure would provide the most accurate mass of the dry precipitate?
Squeeze the precipitate inside the crucible with a clean spatula and blot any visible moisture with filter paper before weighing.
Dry the crucible and precipitate in an oven at 110∘C110^\circ\text{C}110∘C, cool in a desiccator, and weigh; repeat this cycle until a constant mass is obtained.
Evaporate the washings and filtrate to dryness, weigh the residue, and subtract this value from the starting mass of the nickel sample.
Rinse the precipitate with hot ethanol to dissolve and displace the water, then weigh the crucible immediately on the balance.
