MICROCHEMICAL REACTIONS OF STRONTIUM 
341 
and salts of boric acid may sometimes interfere with the forma¬ 
tion of typical crystals of strontium sulphate. 
EXPERIMENTS. 
a. To a drop of moderately dilute solution of SrCh, add dilute H2SO4 and 
examine at once. 
h. Recrystallize SrS04 from H2SO4 and from HCl. 
c. Try to recrystallize SrS04 from HCl in the presence of H2SO4. 
d. Make a mixture of Ca and Sr salts and add H2SO4. Recrystallize the 
product from H2SO4 without having removed the Ca. In another portion remove 
the Ca by extracting with boiling water and then recrystallize the residue. 
B. By Means of Oxalic Acid. 
See directions given under calcium, Method B, page 337. 
The crystals of strontium oxalate are similar to those obtained 
with calcium, but are usually distinctly larger, and crosses, 
prisms, and four-pointed rosettes are more abundant and larger. 
The crystals are either tetragonal or monoclinic depending upon 
whether formed in the cold or separating from hot solutions. 
Precautions. 
To avoid error when testing with oxalic acid, it is always ad¬ 
visable, after the crystals have well formed, to draw off the 
supernatant solution and add dilute sulphuric acid to the pre¬ 
cipitate. If no crystals of calcium sulphate appear after a few 
minutes, add more acid and heat until white fumes appear, care¬ 
fully observing the usual precautions. Transfer the drop of acid 
to a clean slide, breathe on the drop and examine for fusiform 
crystals of strontium sulphate. 
EXPERIMENTS. 
a. Test a drop of SrCb solution with H2C2O4. 
b. Treat the oxalate thus obtained with H2SO4 and recrystallize. 
BARIUM. 
Crystal Forms and Optical Properties of Common Salts 
of Barium. 
A. ISOTROPIC. Nitrate (I). 
B. ANISOTROPIC. 
Hexagonal. — Nitrite. 
