Prof. Miller on the Form of Crystals of Peroxide of Benzoyle. 227 



" On the Form of Crystals of Peroxide of Benzoyle." By William 

 Hallows Miller, M.A., For. Sec. R.S, &c. 



The peroxide of benzoyle, C u H 10 O 4 , or carbon 69*42, hydrogen 

 4*13, oxygen 26*45, was discovered by Professor (now Sir B. C.) 

 Brodie, and described by him in Phil. Mag. S. 4. vol. xvii. p. 301. 

 The crystals were obtained from a solution in ether of the product 

 of the mutual decomposition of equivalent proportions of chloride 

 of benzoyle and peroxide of barium mixed in water. The faces of 

 the crystals, though brilliant, were not very even, so that, in order 

 to obtain a moderately accurate result, it was necessary to measure 

 a large number of crystals. The column headed ' observation ' con- 

 tains the means of the observed angles ; the column headed ' calcu- 

 lation,' the most probable values of the angles, taking into account 

 the quality of the faces containing them, and the number of the ob- 

 servations in each case. 



System prismatic : — 



10 1, 00 1=33° 24'; 1 10, 1 0=57° 50'*5. 

 Observed forms : — 



10, 1, 12, 10 2, 10 1, 1 10, 1 1 I. 



Angles. 



Calculated. 



Observed 



1 2, 1~2 







55 



21 



55 20 



101, 101 



6Q 



48 



66 49 



1 2, 1 2 



36 



30 





1 0, 1 



90 









01, 1 10 



90 









1 1 0, I 1 



64 



19 



64 18 



1 1 1, 1 1 1 



48 



56 





1 1 1, 1 1 1 



- 82 



24 





1 1 1, 1 1 1 



77 



49 





01, 1 1 1 



51 



5 



51 3 



1 1 1,012 



30 



26 





101,012 



42 



19 





101, 1 1 1 



41 



12 





1 1 0, 1 2 



66 



51 





1 1 0, 1 1 



72 



58 





No cleavage observable. 

 The minimum deviations of the brightest part of the solar spec- 

 trum were observed through the faces 1 2, 12, through the faces 



Q2 



