8 OPTICAL ACTIVATION 



The value 0.0174 x 10~^ was obtained by Ostwald for the 

 affinity constant of d- camphor-carboxylic acid at 25°. 



The bromcamphor-carbox;)dic acids were prepared accord- 

 ing to Aschans^ method of 'brominating the corresponding 

 caniphor-carhoxylic acids, in acetic acid solu-tion at room 

 temperature. Aschan obtained a pure acid by crystallising once 

 from ligroin. In spite of a large number of experiments, in 

 which a variety of solvents were employed, I have been unable 

 to obtain a perfectly pure bromcamphor-^carboxylic acid. In 

 ligroin the acid appeared to be almost insoluble. The purest 

 preparations were obtained by recrystallisatioii from a mixture 

 containing a large quantity of ether to a small quantity of 

 alcohol. About 25 grams of acid were shaken up with almost 

 sufficient ether to dissolve it, and then alcohol was added, a few 

 drops at a time, until ihe acid (dissolved. The acid was then 

 allowed to slowly crystallise out from this solution. Especially 

 good crystals were obtained with one of the preparations of 

 1- acid. These were examined and found to consist of a 

 combination of the following three forms of the monioclinic 

 system : 



(i) 



Vertical Prisms. a : mb : o: c 



(ii) 



IClinodoma a a : b : mc 



(iii) 



Ortliopinakoid a : cxb : oc ' 



The lorthopinakoid was very well developed. 



Two different preparations A and B of the d- and 1- 

 acids were made and. in the kinetic experiments which follow, 

 measurements were, as a rule, made with both these prepara- 

 tions. Only one inactive preparation was prepared. The 

 melting points and optical rotation of the different acids were 

 determined ; also analyses were made of the acids, both by 

 titration with barium hydroxide solution and by estimation 



Aschan, C: Ber. d. deutsch. Chem. Ges., 27, 1445, (1894). 



