CrystalHne Forms of Artificial Salts. 



285 



Cleavage. — Parallel to all the faces of the primitive, and 

 also to a plane passing through the two short diagonals of the 

 bases. 



Sulphate of Potash. 



\m' ;(,m 



Primitive form. — Right rhombic prism, the incidence of the 

 two lateral planes of which is 120° 30', and the ratio between 

 one edge of the base and the height, nearly that of 10 to 13. 



Cleavage. — Parallel to all the faces of the primitive form, 

 and also to planes passing through both the diagonals of the 

 bases. 



In many of the small crystals, the faces P, h^, b^, h^, do not 

 occur. 



Hyposulphate of Potash. 



m on ?n 



Incidences. 



. 120° »ionP . . 90° 0' 



.150 a" . . . 143 22 



6i . . , 12r 60 



