332 
ELEMENTARY CHEMICAL MICROSCOPY 
A. ISOTROPIC. 
The alums (I); chloride (I); bromide (I); iodide 
(I); silicofluoride (I). 
B. ANISOTROPIC. 
Hexagonal. — Fluoride. 
Tetragonal. — Borate (NH4)2B407 • 4 H2O; primary 
phosphate. 
Orthorhombic. —Bicarbonate; nitrate;^ primary 
oxalate; normal oxalate; perchlorate; pri¬ 
mary tartrate; sulphate. 
Monoclinic. — Secondary arsenate; bichromate; 
chromate; molybdate; persulphate; ammo¬ 
nium-sodium acid-phosphate; secondary 
phosphate; primary sulphate; ammonium- 
ferrous sulphate; thiocyanate; normal 
tartrate; thiosulphate. 
Triclinic. 
DETECTION. 
Unless the analyst is dealing with a simple salt of ammonium, 
it is always best to expel the NH3 from the compound by distilla¬ 
tion (see page 292) with sodium hydroxide or magnesium oxide. 
The ammonia set free is fixed by absorption in a drop of dilute 
hydrochloric acid (or other acid). The resulting solution of 
ammonium chloride is concentrated or evaporated to dryness 
and the material thus obtained tested for ammonium. 
A. By Means of Chloroplatinic Acid. 
See Method I, page 299, and discussion and precautions 
given under Potassium, test A, page 327. 
B. Through the Formation of Ammonium Magnesium Phos¬ 
phate. 
The typical reaction for this identity test may be written 
NH4CI -f MgCb HNa2P04 + NaOH = 
NH4MgP04 -f- 3 NaCl T H2O. 
^ NH4NO3 is pseudotetragonal. 
