156 MICRO-CHEMISTRY [CH. VI 



It will be seen by the last paragraph that in chemistry as in biology, 

 the microscope is only an aid to investigation ; it cannot take the place of 

 thorough training in the fundamentals of the subject under investiga- 

 tion. 



§ 229. The following list of substances is suggested by Dr. 

 Chamot for beginning practice as the results given are definite and 

 easilv obtained : 



SUGGESTIONS FOR STUDY ON CRYSTAL SYSTEMS 



'Isometric. 



Sodium chlorid, potassium chlorid, potassium iodid. 



Alums, crystallize in octahedra, cubes or combinations of the two. It is 

 well to recall that the alums have the general formula, M 2 (S0 4 ) 3 . N 2 S0 4 24 

 H 2 0, where -M- can be Al, Cr, Mn, Fe, In, Ga, Tl, and -N- Na, K, Rb, 

 Cs, NH, Ag, or Tl. All alums are isomorphous. 



Tetragonal. 



Potassium copper chlorid. Ammonium copper chlorid. 

 Nickel sulfate 6H 2 0. This salt is dimorphic, crystallizing also in the mono- 

 clinic system. Nickel sulfate 7H 2 is orthorhombic. 



Orthorhombic. 



Mercuric chlorid. Silver nitrate. Potassium sulfate. Potassium nitrate. 

 Magnesium sulfate 7H 2 0. Potassium chromate. Sodium nitrate (also 

 Hexagonal). 



Monoclinic. 



Potassium chlorate (sodium chlorate is Isomet. or Tetrag. ) 



Lead acetate. Copper acetate H 2 0. Oxalic acid. 



Ferrous sulfate, this salt forms normally with 7 H 2 and is then Mono- 

 clinic, but in presence of zinc sulfate becomes Orthorhombic, and in presence 

 of copper sulfate, Triclinic. 



Sodium sulfate ioH 2 0. 



Triclinic. 



Copper sulfate 5H 2 0. Boric acid. 

 Hexagonal. 



Lead iodid. Sodium nitrate (also Orthorhombic). 



\ 230. Before performing analytical tests, it is necessary that the student 

 be familiar with the properties of crystals and also thoroughly familiar with 

 the appearance of crystals of the chlorides, nitrates, and sulfates of Sodium, 

 Potassium, and Ammonium ; since some of these salts are sure to appear in 

 almost every test drop examined. For this reason the following experiments 

 should be carefully performed." 



