( 560 ) 



T. at t = :i")0 

 » 25° 

 » 15° 



Acid c, 



'1 cc. 

 58 m. -10 s, 

 2 h. 85 ni. 



3 h. 27 in. 



From the results obtained it appears in the first i)lace thai tiie 

 Iransforiiiatioii is a nioiiomolecidar one and, taking into consideration 

 llie circumstanc3s under which it takes phxce, must be considered 

 as an intramolecular rearrangement of atoms. 



To this conclusion the following observations may be added. 



.1. Tlie influence of the concentration of the acid, the other circum- 

 stances being tlie same, is very great. The coiu-se of the figures leads 

 to the idea that the active agejit, the catalyser is not HsSO^ l)ut SO,. 

 Experiments were tliei-efore made to ascertain how chloroform 

 behaves towards the four acids employed. Whilst from ordinary 

 96 "/j acid (d) but xery minute traces were dissolved, this amount 

 was perceptibly lai-ger with acid c and still larger with acid A, 

 whilst acid a appeared to yield very much SO, to the chloroform ^). 



The idea that SO., is the catalysing substance is consequently^ 

 confii-med. The rapid decrease of the concentration of the acid is 

 also in agreement \\\\\\ this idea ; this velocity is therefore as it 

 were a measure of the concentration of the SO, still present in a 

 sulphuric acid of given concentration. 



B. It is now also very plain that the (juantity of the acid must 

 have a great influence. As shown by its l)ehaviour to acid a, chloro- 

 form may dissolve considerable quantities of SO,. On shaking with 

 sulphuric acid of a lesser concentration, the amount of SO, which 

 passes into the chloroform will consequently depend on the quantity 

 of the acid. The equilibrium for the SO, which distributes itself 

 betweeii the chloroform and the sulphuric acid changes, as is known, 

 with the relative quantities of the two liquids and with the 

 temperature. 



As a consequence of the view taken here, it must be assumed 

 that ordinary 96 "/„ sulphuric acid still contains a minute quantity, 

 of free SO, -molecules. This view is admissible ^) since it is known 



1) The ratio in which different acids yield SO3 to chloroform will be further 

 determined. 



~) Knietsch, in his weil-known research on sulphuric acid, has shown that an 

 acid of 97 — 98 % absorbs SO3 much more readily than acids of smaller or 

 larger concentration. From the results obtained up to the present it does not 

 appear that, in the transformation of tribromophenolbromine, the 98 % acid c 

 behaves in a particular manner; an extension of the research will elucidate this 

 question. 



