132 



PROCEEDINGS OF THE AMERICAN ACADEMY 



Crystalline form of Dichloracrylic Acid. 



001 



ti 



loo 



n^ 



(00 



too 



Monoclinic System. 



Forms, {100} {001} {110} {111}. 



Elements: Clinodiagonal a =1.1865 

 Orthodiagonal b = 1 

 Vertical Axis c = 0.3637 

 Ande of Axes XZ = 87° 32' 



Angles between Normals. 



Observed. Calculated. 



Til andTTl = 37° 54' ^ 

 Til " 001 = 25° 8' [■ Fundamental angles. 

 Til « TOO = 71° 49') 



001 " TOO = 87° 32' 87° 33' 



TOO « TIO = 49° 56' 49° 51' 



TIO " 110 = 80° 6' 80° 18' 



Although Wallach's dichloracrylic acid also crystallizes in the mono- 

 clinic system, the forms are totally unlike, and the ditFerence between 

 the two acids is therefore established. 



