STRONTIUM HYDROXIDE 195copper oxide continuously goes into solution to resupply Cu++
ions. This action continues until either the copper oxide or the
strontium sulphide is exhausted.
Strontium hydroxide crystallizes with 8 molecules of water,
Sr(OH) 2 -8H 2 O. It is very soluble in hot water, but sparingly
soluble in cold water.
Materials: celestite, SrSO 4 ,61 grams = 0.33 F.W.
powdered charcoal, 35 grams,
copper oxide, 48 grams.
Apparatus: gas furnace.
30-gram clay crucible and cover.
large mortar and pestle.
8-inch porcelain dish.
500-cc. flask.
suction filter and trap bottle.
5-inch watch glass.
400-cc. beaker.
iron ring and ring stand.
Bunsen burner.
Procedure: Grind the powdered celestite in a porcelain mortar
until no more grit is felt under the pestle. Add 24 grams of
powdered charcoal and continue to grind with the pestle until the
two are thoroughly mixed. Place the mixture in a clay crucible,
pack it firmly, and cover it. with a layer of powdered charcoal \
inch deep. Cover the crucible with a close-fitting cover and heat
it in a gas furnace for 1 hour, at a bright red heat. After the
contents of the crucible have cooled, remove the layer of charcoal
from the surface and bring the remainder, after crushing it to
a powder, into an 8-inch porcelain dish; add 360 cc. of water,
bring the mixture to a boil, and while it is boiling add copper
oxide, a little at a time, until all of the soluble sulphide has inter-
acted with it — about 48 grams in all. As long as any unchanged
strontium sulphide is present the solution will show a yellow color,
which may be observed by letting the black solid settle for a mo-
ment, and then looking through the upper layers of the clear liquid
at the background of the white porcelain dish. As soon as the
yellow color has entirely disappeared, the strontium sulphide has
all reacted. Crystals of strontium hydroxide separate rapidly
from this solution when it cools. Hence it must be filtered quickly