OF ARTS AND SCIENCES. 203 



The next important step was taken by Cannizzaro,* in 1855, who 

 proved that the product of the action of chlorine on toluol is identical 

 with benzylchloride made from benzylalcohol. Beilstein,f in 18G0, 

 introduced a great deal of confusion into the subject by contradicting 

 Gerhard t'sf inference from Deville's work, that the action of chlorine 

 on cold toluol was different from its action on hot, and describing ex- 

 periments of his own to prove that differences in temperature made 

 no difference in the products. He also thought he had proved the 

 identity of the dichlortoluol from toluol and chlorine with the chloro- 

 benzo! made from benzaldehyde witli phosphoric pcntaehloride, but 

 Cahours, § three years later (I860), announced that they were only 

 isomeric. In the same year (1863), Naquet |j studied trichlortoluol 

 in comparison with the product of the action of phosphoric pentachlo- 

 ride on benzoylchloridc. 



The next important discovery was made in 1865 by Fittig and 

 Glinzer,!! who obtained monobromtoluol by treating cold toluol with 

 bromine, and pointed out the marked differences between it and chlor- 

 toluol (benzylchloride) ; while in 1866 Kekule,** in his paper on 

 aromatic isomeres described benzylbromide made from benzylalcohol, 

 and, after comparing it with monobromtoluol, explained the cause of 

 their difference. 



In this same year (1866), Beilstein, in conjunction with Geitner,tf 

 put the whole subject on a firm basis by the following statement, since 

 known as Beilsteiu's Law: — Toluol behaves differently with chlorine 

 according as it is hot or cold; in the cold, a chlortoluol as stable as 

 chlorbenzol is formed, usually, however, mixed with benzylchloride 

 unless great care is taken in cooling. If hot, the toluol is converted 

 into benzylchloride, but it is not necessary absolutely to boil it, as a 

 very slight increase of temperature is enough completely to prevent 

 the formation of chlortoluol. With iodine only chlortoluol is formed 

 under all conditions, even when the toluol is boiling ; \\ the chlortoluol 

 obtained by this process is however contaminated with substances con- 

 taining iodine. In this paper they predict a similar action with 



* Ann. Chem. Pliariu., xcvi. 240. \ Trade' de Chimie, iii. 507. 



t Ibid., cxvi. 006. § Comptcs Rendus, Ivi. 222. 



|| Comptcs Rendus, Iv. 407, lvi. 129. 



IT Ann. Chem. Pharm., exxxiii. 47, exxxvi. 801. 

 ** Ibid., exxxvii. 188. tt Ibid., exxxix. 831. 



XX The use of iodine was suggested by the paper of II. Miiller (Journal Lon- 

 don Client. Soc, xv. 41) on making chlorine substitution products front benzol 

 in presence of iodine. 



