CUPROUS OXIDE 225move the filter paper, and break up the cake. Rest the watch
glass on a wooden ring or on a beaker and set in on the hot plate.
As soon as the odor of ether has disappeared, pulverize the product
and put it into a 2-ounce bottle which has been thoroughly dried.
The product should be pure white.QUESTIONS- Explain why copper does not reduce cupric sulphate to cu-
prous sulphate. - Place 0.5 gram of cuprous chloride in the bottom of a dry
test tube. Fill it completely with 6N NH4OH and immediately
stopper it tightly, allowing no air bubble to remain at the top.
Invert the tube a number of times until the salt is dissolved. At
this point, the solution should be nearly colorless, and it would
be quite so if the salt had been pure and air had been completely
excluded. Pour the solution into an open beaker and note the
change in color. Equations? - Spread about 0.5 gram of cuprous chloride in a watch glass;
moisten it, and let it stand 5-10 minutes. What causes the
discoloration? Equation? Rinse the discolored mass into a
beaker and add 1-2 cc. 6N HC1. What causes the solid to
again become white and the solution blue? Equation?
PREPARATION 29
CUPROUS OXIDE, CU 2 O
When metallic copper is heated in the air it becomes coated
with a layer of oxide, which, according to conditions, may be
cuprous or cupric oxide, or a mixture of the two. Pure cuprous
oxide is most conveniently prepared in the wet way by treating
an alkaline cupric salt solution with a reducing agent, whereby
the red cuprous oxide is precipitated.
Cupric hydroxide is nearly insoluble in NaOH solution alone, but
it dissolves when a soluble tartrate is added, the copper going into
a complex negative ion similar in color to the ammonio-cupric ion.
Materials: blue vitriol, CuSO 4 -5H 2 O, 50 grams = 0.2 F.W.
Rochelle salt, KNaCJ^Oe-il^O, 75 grams,
sodium hydroxide, 75 grams,
dextrose, 10 grams.
95% alcohol, 45 cc.