1865.] Destructive Distillation of the Sulphobenzolates. 35.1 



X = 0r wq, ~Y = wp ur, Z=uq vp, 



and nr 2 is a numerical factor. 



Each of these equations is of the degree 18w 36 in the variables ; but 

 it is shown in the paper that they are all divisible by H, and that they 

 further differ only in respect of the several factors u 3 , v 3 , w 3 . Dividing 

 these out, the degree of the result is reduced to 



(18-36)-3 ( n -2)-3 (-!)= 12/1-27, 



as it should be. I have riot thought it necessary to reduce the expressions 

 completely, as the form of the result given by Professor Cayley leaves 

 nothing to be desired, and the point specially considered here is the degree 

 of the equation. At the same time, the redactions necessarily effected in 

 the course of the proof of the extraneous factors are sufficient to indicate 

 that the formulae of the present memoir would lead to an equation of the 

 same form as that given by Professor Cayley. 



XL " Products of the Destructive Distillation of the Sulphobenzolates. 

 No. I." By JOHN STENHOUSE, LL.D., F.R.S., &c. Received 

 June 14, 1865. 



Preparation of Sulpholenzolic Acid. Purification of the Eenzol, 

 As most specimens of benzol met with in commerce, even when rectified, 

 contain impurities besides toluol and the other homologues of benzol, I 

 have generally found it necessary to submit it to purification before using 

 it for the preparation of sulphobenzolic acid. The commercial article boil- 

 ing between 80 and 90 C., was mixed with about one-twentieth of its 

 bulk of concentrated sulphuric acid, and digested for eight or ten hours in 

 a flask furnished with a long condensing- tube. By this means a consider- 

 able amount of the impurities contained in the crude benzol were con- 

 verted by the acid into a black gelatinous mass similar in appearance to 

 that obtained in the preparation of olefiant gas, a large quantity of sul- 

 phurous acid gas was given off, and the impure benzol acquired a reddish- 

 brown or dark purple colour. It was separated from the black mass, 

 washed with a small quantity of water, and again heated once or twice 

 with concentrated acid, but for a shorter time than at first, until fresh 

 acid when heated with it ceased to become dark-coloured. In this opera- 

 tion the benzol loses from 10 to 20 per cent., according to the amount of 

 impurity present, and small quantities of sulphobenzolic acid are produced. 



Conversion of Benzol into crude Sulphobenzolic Acid. 

 This acid may be prepared by the process given by Mitscherlich, which 

 consists in adding benzol to fuming oil of vitriol contained in a flask, as 

 long as it dissolves, with agitation and frequent cooling. Notwithstanding 



