( 565 ) 



symmetiy-plane or a symmetry centre; but only one single unipolar, 

 twin axis. All the crystals which I investigated represented the same 

 variety of the two possible enantiomorphous forms. 



Fig. 1. d. Fructose tetracetate (Brauns). 



The symmetry assigned here to the crystals is not only proved 

 by their habit, but also proved beyond all doubt by the investigation 

 of the etched figures obtained by means of 957o alcohol; these were 

 very distinct particularly on jlOOj and jOOlj. 



Parameters -. a-.b-.c^l, 3463 : 1 : 1, 5733 

 /i=52".J2' 

 Forms observed: c = |00i|, broad and very shining; a = {100|, 

 somewhat narrower; o = \lll\, large and yielding sharp reflexes; 

 q=^\Oil\, small but reflecting well; Q=i\011\, large and shining; 

 ?' = |r02|, very narrow and dull; .^' = |911| exceedingly narrow and 

 measurable only with difficulty. Once or twice one plane of |lll| 

 was observed, rudimentary and striped parallel to the plane jOOlj. 



Angular values-. Measured: 



c:a = (001) : (100) =:* 52M2' 

 0:0 — (ill) : (llT) =* 75 .41 

 c:o = (0öl):(ll-l)=*79 .37 



a:^=(100):(011)rrr 67 .217, 



q:o = (Oil) : (Til) = 43 .107, 



x:o = (911) : (111) = 60 .44 (about) 



x:a={dn): (100) = 8 .36 (about) 



rt:0=(100):(llï)= 69.297, 



q:q= {Oil) ■.{011)= 77.39 



c:g=(001):(01J)= 51.107, 



C:r=: (001): (102)=: 35.44 



r: a = (102): (100)=: 92.4 



Calculated: 



67°.247,' 

 48 .177, 

 60 .537, 

 8 .277, 

 69 .207, 

 77 .377, 

 51 .117, 

 35 .43\/, 

 92 .47, 



