8 OPTICAL ACTIVATION 



The value 0.0174 x 10~ 2 was obtained by Ostwald for the 

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



The bromcamphor-carboxylic acids were prepared accord- 

 ing to Aschan s 1 method of 'brominating the corresponding 

 camphor-carboxylic acids, in acetic acid solution 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 recrystallisation 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 ;the 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 monoclinic 

 system : 



(i) Vertical Prisms. a : nib : a c 



(ii) Klinodonm oc a : b : me 



(iii) Orthopinakoid a : ocb : oc c 



The orthopinakoid 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 



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



