198 ALKALI AND ALKALINE EARTH METALSApparatus: 8-inch porcelain dish.
600-cc. beaker,
mortar and pestle,
iron ring and ring stand.
Bunsen burner.Procedure: Grind the powdered celestite in a mortar until
it is so fine that it no longer feels gritty under the pestle. Cover
it in an 8-inch porcelain dish with 360 cc. of water, add the anhy-
drous sodium carbonate, and boil the mixture for 30 minutes, stir-
ring it constantly at first. Transfer the solution and solid to a
600-cc. beaker, using 100 cc. of fresh water in rinsing out the last
of the residue, and let the solid matter settle for 5 minutes. De-
cant off the liquid, which is still somewhat cloudy, but from which
the essential part of the solid has settled, and wash the residue
three times by decantation with 400-500 cc. of water. (See first
paragraph, Note 5 (6), page 10). The residue is now sufficiently
free from soluble sodium sulphate. Transfer about one-tenth of the
moist strontium carbonate to another beaker, to be used in a later
part of the process. To the remaining nine-tenths add 50 cc. of
hot water, and then add hydrochloric acid, drop by drop, while
stirring the mixture, until the further addition of a drop of acid
produces no more effervescence. This solution now contains a
slight excess of acid, and probably a trace of iron chloride as im-
purity. Add a few drops of chlorine water to oxidize any ferrous to
ferric salt, then add the remaining one-tenth of the strontium car-
bonate and boil the mixture for 5 minutes. The solution should
now be perfectly neutral to litmus, in which case all iron will
be precipitated as Fe(OH) 3. If it is acid, it shows that the
hydrochloric acid was added carelessly and that there was thus
more than could be neutralized by the strontium carbonate. Filter
the perfectly neutral solution, and evaporate the filtrate until a
faint scum forms on removing the solution from the flame and
blowing vigorously across the surface. Allow the solution to cool,
but stir occasionally in order to obtain a uniform crystal meal
rather than a cake of crystals. Finally, drain the crystals on a
suction filter (Note 4 (6), page 6); evaporate the mother liquor
to crystallation exactly as at first, and if the second crop of crystals
is pure white, add it to the first crop. Wrap the crystals of
SrCl 2 -6H 2 O in paper towels and leave them over night to dry