CRYSTALLIZATION EXPERIMENTS 
271 
Isometric System. 
Sodium chloride; potassium iodide; barium nitrate; ammonia alum; chrome 
alum; arsenic trioxide; sodium chlorate (circular polarization). 
Hexagonal System. 
Lead iodide; iodoform; cadmium iodide; normal sodium phosphate; strontium 
chloride; strontium antimonyl tartrate; sodium nitrate. 
Tetragonal System. 
Potassium arsenate; mercuric cyanide; potassium copper chloride; urea; 
strychnine sulphate; primary ammonium phosphate; primary potassium phos¬ 
phate. 
Orthorhombic System. 
Ammonium sulphate; mercuric chloride; potassium antimonyl tartrate; po¬ 
tassium nitrate; potassium sulphate; sodium nitroprusside; zinc sulphate; uranyl 
acetate. 
Monoclinic System. 
Potassium ferrocyanide; potassium ferricyanide; sodium ferric oxalate; ammo¬ 
nium persulphate; potassium chlorate; barium chloride; nickel chloride; tartaric 
acid; saccharose; potassium magnesium sulphate. 
Triclinic System. 
Copper sulphate; potassium bichromate; potassium persulphate; boric acid; 
manganous sulphate. 
Pleochroic Salts. 
Copper acetate; iodoquinine sulphate; potassium (or sodium) ferric oxalate; 
potassium cobalt sulphate; silver bichromate; potassium chromium oxalate. 
In a watch glass place a few drops of benzene, add a few crystals of quinone, 
stir until dissolved. .A.dd a few crystals of resorcin, stir. Remove a drop to a 
slide and allow it to deposit crystals by spontaneous evaporation. The crystals 
will be found to be strongly pleochroic. 
All the compounds listed above are easily crystallizable. 
Most of them are soluble in both hot and cold water. The 
exceptions to this rule are: (a) strontium antimonyl tartrate 
more soluble in ice cold water than in hot water; (b) lead iodide, 
cadmium iodide almost insoluble in cold water, soluble in hot 
water, (c) iodoform, iodoquinine sulphate, insoluble in water, 
soluble in alcohol, (d) silver bichromate practically insoluble 
in water, soluble in dilute nitric acid or in dilute ammonium 
hydroxide. 
All the compounds given should have yielded, under the 
conditions of the experiments, normal, typical, well-developed 
crystals whose habits could be easily recognized. Had we forced 
the crystallization too rapidly, or had there been one or more 
other compounds present, or had colloids been present such as 
gums, resins, mucilages, etc., then instead of well formed crys- 
