METHOD OF OBTAINING STRONTIA. 243

tracts carbonic acid strongly from the atmosphere, becomesslaked and swells up. It heats much and hardens strongly withwater. It is not fusible by the blow-pipe, but becomes extremelyphosphorescent. It tinges the flame of burning bodies carmine-red if moisture be present. It is soluble in 200 parts of water atthe common temperature; boiling water dissolves it readily; andthe solution on cooling shoots into regular crystals; these are thin .quadrangular plates, sometimes square, oftener parallelograms.It has a great attraction for acids, but adheres to them with lessforce than barytes, and even with less than potash and soda. Itcombines with combustible bodies such as sulphur, phosphorus,Ac. It is not poisonous to animals.

METHOD OF OBTAINING STRONTIA.

Strontia may be obtained from its native combinations byprocesses similar to those by which barytes is obtained (seepage 223). It may also be procured by exposing the native carbo-nate of strontia to heat; care however must be taken not to havethe fire too strong as the strontia in that case attacks theearthen crucible. The former methods are therefore preferable.In order to obtain it from sulphate of strontia, let a quantity ofthis mineral be reduced to powder; mix it with about one-sixthpart of its weight of charcoal powder, and keep it for somehours red hot in a crucible. Then dissolve the mass in water,and pour nitric acid into the solution so long as a precipitateensues. The solution is then to be filtered, evaporated till astrong pellicle appears, and suffered to crystallize. These crystalsof nitrate of strontia may then be decomposed by exposing them toheat till all the nitric acid is driven off, which may be known byholding a piece of ignited charcoal over the fused nitrate, if theflame of the charcoal does not become enlarged the acid is dispel-led. In order to obtain it crystallized it may be dissolved inboiling water, evaporated, and suffered to cool.

Q 2