MICROCHEMICAL REACTIONS OF STRONTIUM 
339 
A. ISOTROPIC. Nitrate (I). 
B. ANISOTROPIC. 
Hexagonal. 
Tetragonal. 
Orthorhombic. — Chlorate; sulphate. 
Monoclinic. — Acetate; chromate. 
Triclinic. — Chloride. 
DETECTION. 
A. By Means of Sulphuric Acid. 
First obtain a precipitate of strontium sulphate by 
Method I, page 299. Examine it with the microscope to learn 
the character of the solid phase. Then proceed with the identi¬ 
fication of the practically amorphous precipitate by recrystal¬ 
lization from concentrated sulphuric acid by Method XII, 
page 312, or from concentrated hydrochloric acid by the same 
method. 
Rarely, strontium sulphate separates in the cold in crystal 
form. Heating with concentrated sulphuric acid and gently 
breathing upon the preparation yields at first globular masses 
and tiny rhombic plates of a salt of the formula SrS04 (or some¬ 
times probably SrS04 • H2SO4). These tiny plates eventually 
develop into more or less irregular spindle-shaped crystals, 
which gradually enlarge at the middle until they become irregular 
crosses with two very short arms. The appearance is very 
characteristic. The only element liable to lead to error is lead 
which often first assumes forms closely resembling those of stron¬ 
tium, later growing into crystallites which may be mistaken for 
barium. 
Recrystallized from concentrated hydrochloric acid strontium 
sulphate has an entirely different habit. Square and rectangular 
plates appear followed by thin prisms and sheaves of slender 
pointed crystals. The solubility of strontium sulphate even in 
hot hydrochloric acid is quite low, hence it is necessary to employ 
a large drop of the solvent and even so it is seldom that all the 
precipitate will dissolve. It follows that to obtain the best results 
the solvent should be decanted from the precipitate immediately 
