CRYSTALLIZED COPPER SULPHATE 221laboratory, nitric acid instead of air will be employed as the
oxidizing agent.
3Cu + 2HNO 3 = 3CuO + H 2 O + 2NO
CuO + H2SO4 = CuSO 4 + H 2 OMaterials: copper turnings, 64 grams = 1 F.W.
6.ZVHNO3.
QN H 2 SO 4.
Apparatus: 6-inch iron sand bath.
8-inch porcelain dish,
suction filter and trap bottle.
8-inch crystallizing dish with glass plate,
iron ring and ring stand.
Bunsen burner.Procedure: Heat the copper turnings in an iron pan until all
oily matter is burned off and the metal has become coated with
oxide. In an 8-inch porcelain dish treat the ignited copper turn-
ings with the calculated volume of 6N H2SO4 and 6N HNO 3.
Warm in the hood for 20 minutes; if any metallic copper remains
undissolved, pour the solution off from it and treat it with a few
cubic centimeters of fresh nitric acid and twice as much sulphuric
acid. If the solution is not perfectly clear, filter it while still at
the boiling temperature; then cool as rapidly as possible, stirring
to get a crystal meal. Separate the meal from the mother liquor,
using the suction filter. Evaporate the mother liquor somewhat,
and obtain a second crop of crystals, discarding the mother liquor
from this crystallization. Dissolve all the damp product by add-
ing its own weight of water and warming; place the warm solution
in the crystallizing dish, add some seed crystals when the tempera-
ture is about 35°, cover the dish, wrap it with towels, and leave it
to cool very slowly. Remove the crystals, and leave the saturated
solution in the crystallizing dish uncovered to evaporate slowly
and deposit more crystals. Spread the entire product on paper
towels to dry, and hand in the preparation in an 8-ounce cork-
stoppered bottle.
QUESTIONS- Explain why copper will not dissolve in dilute sulphuric acid.
- Write the equation for the reaction of copper with con-