EXPERIMENTS 287gently until the reaction starts. Stop heating until the reaction
slows down, then heat cautiously to boiling, and keep at that tem-
perature for 5 minutes. Cool, filter without suction into the 2-
liter bottle. To remove iron from the solution proceed according
to the same principle as in the preparation of cerous oxalate.
Prepare cerous carbonate by adding an excess, about 5 grams,
Na 2 CO 3 to one-tenth of the cerous chloride solution. Wash the
cerous carbonate by decantation (see Note 5 (6), page 10) until
the soluble sodium chloride is completely removed. Add the
cerous carbonate suspension to the main part of the cerous chloride
solution; digest with frequent stirring for 15 minutes or longer.
Remove the ferric hydroxide and excess cerous carbonate by
filtering, add 5 cc. 12 N HC1 to the filtrate, and evaporate in
the 8-inch porcelain dish to 70 cc. Pour into a small crystallizing
dish, cover with a 5-inch watch glass, cool slowly. Remove the
crystals; dry them on a watch glass. Allow the solution to
evaporate in an uncovered dish to obtain an additional crop of
crystals. Put up the product in an 8-ounce cork-stoppered bottle.
QUESTIONS
Answer the questions under Cerous Oxalate.Experiments- Carbon Dioxide. From a generator (Note 13 (a), page
- fill with carbon dioxide several test tubes inverted in a
pan of water, and use them in the following experiments.
(a) Place the thumb over the mouth of a test tube of
carbon dioxide and transfer it to a beaker of freshly drawn
water. Clamp it in position and note the level of the water
at intervals of about 15 minutes.
(b) Stick a gummed label on a second test tube of the gas,
and make a light pencil mark at the middle point of the
length of the tube. Place the thumb over the mouth of this
tube, remove it from the water, and turn it upright. Draw
some fresh water from the tap, and, removing the thumb
sufficiently, pour water into the tube until the level stands
at the pencil mark. Close the tube again tightly with the
thumb, invert the tube, and place a heavy mark at the level
of the surface of the water, calling this mark 1 (it will of course