1879.] ^45 [Greene. 



and silver. The denarii of Otho are of not infrequent occurrence, not- 

 withstanding the extremely short duration of his reign. 



We cannot more appropriately conclude this sketch than with the words 

 of the Spanish writer, Gusseme: 



"No pretendo que la aficion a las medallas sea la unica; pero si que no 

 se olvide, que no se abandone, antes si que se cultive. Ella es de tal calidad, 

 que siempre recrea, que ofrece a cado paso nuevas satisfacciones, y con una 

 solidez, que no se holla con tanta frequencia en los demas estudios. * * * 

 La Erudition debe ser en todos tiempos, y en todas Naciones apetetida y 

 solicitada ; y seguramenle no hay modo para adquivirla con mayor exten- 

 sion que el uso de los medallas, el esludio para su perfecto conocimienxo., y el 

 manejo de los libros que tratan de ellas. Quien las cultiva va adquiriendo 

 de grado en grado los mas utiles conocimientos, y una vasla extension en el 

 campo de las bellas lettras. 



" Cada medulla es un diploma o instrumento autentico ; que comprueba 

 la verdad de la Historic/, ; y no habrd en el mundo archivo de mas seguros 

 y antiguos documentos. * * * * El estudio de la antiguedad es cosa 

 que no debemos jamas olvidar y abandonar segun Claudiano ; 



Nee desinat unquam 

 Tecum Graia loqui, tecum Romana ■vetustas." 



On the Formation of Dibenzyl by the Action of Ethylene Chloride on Benzol 

 in the Presence of Aluminium Chloride. By William H. Greene. 



{Read at the Meeting of the American Philosophical Society, October 17, 1879. ) 



By a series of the most remarkable chemical investigations of late years, 

 MM. Friedel and Crafts have shown that the radicles of the saturated hy- 

 drocarbons can be grafted upon the benzol nucleus by the action of alu- 

 minium chloride upon a mixture of benzol and the monatomic chlorides, bro- 

 mides, etc. Thus, on passing methyl chloride into benzol in which alu- 

 minium chloride is suspended, all of the methyl derivatives of benzol, from 

 toluol to hexamethyl benzol, may be formed, according to the proportions 

 of benzol and methyl chloride which are brought into contact. In the 

 same manner, the ethyl, propyl, and other derivatives of benzol may be ob- 

 tained abundantly. 



In these reactions, hydrochloric acid is disengaged, and the explanation 

 proposed by Friedel and Crafts supposes the reaction to take place in two 

 phases : In the first, a compound of benzol and aluminium chloride is 

 formed, with elimination of hydrochloiic acid. 



C 6 II 6 + A1 2 C1 6 = C 6 H 5 . APC1 5 + HCl 



In the second, the aluminium-benzol compound reacts upon the mona- 



