1869.] 



On the Action of Bromine upon Ethylbenzol. 



123 



plane geometry, but already very prominently in solid geometry ; viz. we 

 have here the difficulty as to the form of the equations of a curve in space, 

 or (to speak more accurately) as to the expression by means of equations 

 of the twofold relation between the coordinates of a point of such curve. 

 The notion iu question is that of a Z:-fold relation, — as distinguished from 

 any system of equations (or onefold relations) serving for the expression of 

 it, — and giving rise to the problem how to express such relation by means 

 of a system of equations (or onefold relations). Applying to the case of solid 

 geometry my conclusion in the general theory, it may be mentioned that I 

 regard the twofold relation of a curve in space as being completely and pre- 

 cisely expressed by means of a system of equations (P=0, Q=0, . . T = 0), 

 when no one of the func ions P, Q, . . . T, as a linear function, with 

 constant or variable integral coefficients, of the others of them, and 

 when every surface whatever which passes through the curve has its 

 equation expressible in the form U=AP+BQ . . . + KT, with constant 

 or variable integral coefficients, A, B . . . K. It is hardly necessary to 

 remark that all the functions and coefficients are taken to be rational func- 

 tions of the coordinates, and that the word integral has reference to the 

 coordinates. 



IV. "On the Action of Bromine upon Ethylbenzol." By T. E. 

 Thorpe, Ph.D. Communicated by H. E. Roscoe, Ph.D. 

 Received November 11, 1869. 



In the course of an investigation upon ethylbenzoic acid which Prof. 

 Kekule and I recently published in conjunction, we had occasion to pre- 

 pare a quantity of monobromethylbenzol, C 6 H 4 Br{C 2 H 5 . Our object iu this 

 research was to prove experimentally the identity of the ethylbenzoic acid 

 made synthetically by acting upon the monobromethylbenzol by means of 

 carbonic anhydride and sodium, 



C 6 H 4 Br{C 2 H„+Na,+CO=C, H, {^J aQ + Br Na, 



with the acid subsequently obtained by Fittig by oxidizing diethylbenzol, 



q 2 jjj, by means of nitric acid. 



In the preparation of the bromide for the purposes of our experiments, 

 we followed the direction given by Fittig and Konig, by whom this sub- 

 stance was first described. Bromine was added drop by drop to well-cooled 

 ethylbenzol in the proportion of 1 mol. bromine to 1 mol. ethylbenzol, and 

 the mixture was allowed to stand one or two days before distillation. The 

 action of bromine upon ethylbenzol is extremely energetic, each drop of 

 the bromine disappears almost immediately on coming in contact with the 

 hydrocarbon, the mixture, unless carefully cooled, becomes very hot, and 

 large quantities of hydrobromic acid are evolved. It is easy to perceive 

 when the proper point in the substitution is reached, since after the addi- 

 tion of the theoretical quantity of bromine in order to form C 6 Br{C 2 H 5 , 



