196 ALAKLI AND ALKALINE EARTH METALSin order to avoid having the crystals form in the filter and clog it
completely. Heat 50 cc. of water to boiling in a beaker, and keep
it at this temperature until it is required. Add hot water to the
dish to replace any lost by evaporation, and pour (Note 2, page 4)
the hot solution through a large ordinary filter (Note 4 (c), page
7), catching the filtrate in a 500-cc. flask, and allowing the main
part of the residue to remain in the dish. Add the 50 cc. of hot
water to this residue, stir it thoroughly, heating it for a moment
over the flame, and then pour solution and residue into the filter
and drain out all the liquid. In order to lessen the rate of cooling
of the liquid in the filter funnel the latter should be kept covered
with a watch glass. Stopper the flask to exclude the air, and
wrap it with a towel, so that the solution may cool slowly and
larger crystals may be formed. Finally, after several hours cool
the solution with running tap water and then collect the crystals
on a suction filter. Drain the crystals for a moment, but do not
draw too much air through them, as they retain all the carbon
dioxide it contains. Wrap the product in paper towels and leave
it to dry over night at room temperature. (See Note 9 (6),
page 15.) Put the product in a 6-ounce cork-stoppered bottle.
QUESTIONS- What constituent of the atmosphere must be excluded from
the solution while crystallizing and from the crystals while drying?
How would it contaminate the preparation? - A sample of the preparation should dissolve nearly clear in
hot water. What will surely cause a slight cloudiness? - How could strontium chloride be prepared from strontium
sulphide? - Give some other method by which strontium hydroxide
could be obtained from strontium sulphide without the use of
copper oxide. - Starting with the mineral strontium carbonate, how might
strontium hydroxide be prepared? Strontium oxide? Strontium
chloride?
PREPARATION 21
STRONTIUM CHLORIDE FROM STRONTIUM SULPHATE, SrCl 2 -6H 2 O
Strontium chloride might be prepared by treating strontium
sulphide, the intermediate product in the last preparation, with
hydrochloric acid, but, to avoid the hydrogen sulphide nuisance,