OF ARTS AND SCIENCES. 349 



This result, it seems to us, throws light on the beautiful method of 

 ' preparing trisulphouic acids, the application of which to toluol was 

 published by Claesson* in 1881, and which consists in heating a po- 

 tassic sulphouate with chlorsulphonic acid, since it makes it probable 

 that the reaction is due to the acid potassic sulphate formed during 

 the process, rather than to the chlorsulphonic acid itself. In a gen- 

 eral way also our process resembles that of Neville and Winthert for 

 converting the amido compounds into their monosulphonic acids by 

 the action of heat on their acid sulphates, although it is doubtful 

 whether the mode of action of the two processes is the same, since in 

 ours the presence of an excess of sulphuric acid is essential. 



As our process converts the benzoltrisulphouic acid from one of the 

 least into one of the most accessible of the less common aromatic com- 

 pounds, we have devoted some time to its study, and in this paper, 

 after giving the details of our preliminary experiments, and the meth- 

 ods for preparing the benzoltrisulphonic acid, we describe the first 

 results that we have obtained ; which consist of the determination of 

 the crystalline form and solubility of the potassium salt, t the prepa- 

 ration and study of the chloride, the ester, which exhibits a strange 

 instability, the amide with several of its metallic derivatives, and its 

 benzoyl compound, and as this, like the corresponding compound of 

 the benzolmonosulphamide is an acid, its sodium and barium salts 

 and chloride with the phenylamidine derived from it, the anilid, and 

 finally the proof by two different methods that the benzoltrisulphonic 

 acid has the symmetrical constitution 1, 3, 5. 



Formation of Benzoltrisulphonic Acid. 



To prove that the presence of potassic sulphate was the cause of 

 the formation of the trisulphonic acid, a solution of benzol in fuming 

 sulphuric acid, to which its own volume of common sulphuric acid had 

 been added, was divided into two equal parts, (a) and (b), and, after 

 adding a quantity of potassic sulphate to (o), both parts were heated 

 in retorts under precisely the same conditions until half of the liquid 

 had passed over. The residues were converted into potassium salts, 

 and recrystallized, when (a) furnished the very characteristic crystals 

 of the potassic benzoltrisulphonate, and gave a chloride which, after 

 washing with ether and one crystallization from chloroform, melted at 



* Ber. d. ch. G., 1881, p. 307. t Ibid., 1880, p. 1940. 



t Also some attempts to prepare substituted trisulphonic acids, which led to 

 negative results. 



