79 



(210) 



corroded faces. The form is biconvex, 

 pointed upward and downward. 



(ПО) 



(301) 



Fig. 22. Etching figures on {301} 

 produced by acids. 



(Fig. 22) Both sides are curved to an 

 equal degree; the figure is symmetrical 

 to the right and left, the part turned 



Pig- 2Ï- downward is more pointed than that turned 



Etching figures on л m. о i i-.,i i. 



{210} produced by acids. "P^'^^"^' ^he figures vary only a little by 

 using different acids. 

 P{lOl} is very highly corroded, and is always provided 

 with large, distinct etching figures. 



(101) 



(101) 



(021) 



(021) 



(021) 



(111> 



Ô 



Ô 



ÔÔ 



Ô 



(iio)\ 



(111) 



О 



о 



О 



(iIo)\ 



(m; 



/(120) 



(301) (301) 



Fig. 23. Etching figures on {101} Fig. 24. Etching figures on {101} 

 produced by acids. produced by HF. 



(Fig. 23) The form is generally as the above, pointed up- 

 ward towards the edge formed with (lOT), and rounded down- 

 ward. The figures become narrower, when etched with H^SO^. 



