OF ARTS AND SCIENCES. 307 



in 1868. The salt was thus obtained in colorless needles which 

 gave with baric chloride glistening crystals of (C 7 H 6 ClS0 3 ) 2 Ba. H 2 ; 

 the acid (made from the barium salt with sulphuric acid) formed 

 when heated with an excess of plumbic hydrate, a basic lead salt, 

 (C 7 H 6 GS0 8 ) 2 Pb . Pb0 2 H 2 , crystallized in scales with a silvery lustre ; 

 while with less plumbic hydrate a neutral salt was obtained, which, 

 however, he did not analyze. All these salts were made from ordi- 

 nary chlorbenzylchloride, and must therefore have been contaminated 

 with the corresponding ortho compounds, as indeed was proved by 

 Vogt and Henninger,* who took up the subject again in 1872, and 

 by fusing the potassium salt (made according to Bohler's method) 

 with potassic hydrate obtained a mixture of salicylic and paraoxy- 

 benzoic acids. They did not try, however, to separate the para from 

 the ortho compound, but contented themselves with analyzing Bohler's 

 potassium and barium salts : for the first they found the formula 

 C r H 6 ClS0 3 K . H 2 ; it crystallized from water in concentric groups of 

 large flat needles, from alcohol in pearly plates, lost its water of crys- 

 tallization at 160°, and was decomposed at higher temperatures; their 

 barium salt agreed in amount of water of crystallization and proper- 

 ties with that of Border, except that it crystallized in bunches of nee- 

 dles. In preparing their potassium salt Vogt and Henninger observed 

 the formation of an insoluble substance which, purified by crystalliza- 

 tion from alcohol, melted at 167° and had the formula (C 7 H 6 C1) 2 S0 2 ; 

 from the mother-liquors small quantities of two other substances were 

 obtained, melting at 149° and 185°, and apparently having the same 

 composition ; they supposed, therefore, that the main product (melt- 

 ing-point 167°) was a mixture of these, and called it chlorinated 

 benzylosulphide, — a name which, according to our present nomencla- 

 ture, would be altered to dichlorbenzylsulphone. For a revision of 

 their work on this substance, see page 314. 



In taking up the subject we followed the method of our predeces- 

 sors, except that we used sodic instead of potassic sulphite,t which 

 we made by saturating one half of a strong solution of sodic carbo- 

 nate with sulphurous dioxide, and then adding to it the other half. 

 After boiling this solution with parachlorbenzylbromide, in the pro- 

 portion of one molecule of bromide to one of sulphite, in a flask with 

 a return-cooler for seven hours, the smell of the benzylbromide had 

 disappeared ; the liquid was therefore allowed to cool, and the insol- 



* Vogt and Henninger, Ann. Chem. Pharm. 165, p. 372. 

 t Potassic sulphite is to be preferred, however. See p. 309. 



