OF ARTS AND SCIENCES, 351 



it was formed in large quantity in (c), and, if anytliing, was accom- 

 panied with less of the tarry secondary products than when potassic 

 sulphate was used, so that argentic sul[)hate could perhaps be used 

 advantageously in place of potassic sulphate in the manufacture of the 

 trisulphonic acid, since, owing to its slight solubility, it can be filtered 

 out with little loss after the addition of water to the product of the 

 reaction, and is then ready to use again after drying. It follows from 

 the above results that the salt does not act as a dehydrating agent, but 

 rather as a carrier of the sulphuric acid, owing to the formation of an 

 acid salt. 



The experiments just described have led us to the following hy- 

 pothesis to explain the formation of the benzol trisulphonate by the 

 action of potassic sulphate and sulphuric acid ; but we wish it dis- 

 tinctly understood that we could find no way of submitting this bypoth- 

 esis to a complete experimental proof, and therefore oflfer it simply as 

 the most plausible explanation of the observed facts that we have been 

 able to find. The acid potassic sulphate formed by the sulphuric acid 

 and potassic sulphate is first, we suppose, converted into the potassic 

 pyrosulphate by loss of water, and the pyrosulphate in its turn decom- 

 posed by the sulphuric acid, giving potassic sulphate and fuming sul- 

 phuric acid, which, breaking up into Il2S0^ and SO.,, furnishes the 

 nascent sulphuric anhydride to form the benzoltrisulphonic acid, while 

 the potassic sulphate goes through the same series of reactions again, 

 which can be written as follows : — 



K2SO, -f H,SO, = 2 KHSO, 



2 KHSO, = K2S2O, -f H,0 



K^^^Ot + H,SO, = K2SO, + H,S,0- = K.SO, + H,SO, + SO3. 



Of these reactions the second can be considered well established, since 

 the proportion of acid to potassic sulphate in the mixture used by 

 us is almost exactly one molecule of K„SO^ to two of H.,SO^ ; and 

 it has been found,* when such a solution is allowed to cool, that it 

 deposits first the neutral salt KgSO^, and afterward the potassic pyro- 

 sulphate KoSsO?- l^ut the last reaction is certainly not above criti- 

 cism, since in it sulphuric acid is made to displace pyrosulphuric acid, 

 which last, it is fair to suppose, is the stronger of the two. In answer 

 to this we would suggest, that the reaction either may be brought un- 

 der Berthollet's law on account of the formation of the' volatile sul- 



* Gmelin Kraut., 1875, ii. 48. 



