MR. WATSON SMITH ON ISODINAPHTHYL. 



17 



trated sulphuric acid (about 5 p. c. by volume) ; and, after 

 separating, it was again shaken with hot caustic soda so- 

 lution of sp. gr. = 1*18. The naphthalin thus treated was 

 now purified by fractional distillation, the portion boiling 

 between 210 C. and 21 2° C. being kept. After another 

 distillation, the perfectly white product obtained was 

 taken for experiment. Into a small flask (a) 152*6 grms. 



a. Small flask with naphthalin. 



b. ^-inch iron tube, filled with small fragments of charcoal. 



c. Retort, to collect distillate. 



d. Gas-jar, to collect and measure gas evolved. 



of the pure naphthalin were introduced, and the flask was 

 connected with an iron tube (^ inch diameter) filled with 

 small fragments of charcoal, to afford a large heated sur- 

 face. That charcoal had no chemical influence beyond 

 that of affording a large heated surface, was proved by the 

 fact that the same results were obtained when fragments 

 of pumice stone, soda-lime, brick, or the empty tube itself 

 was employed. With the other end of the iron tube was 

 .connected a bent glass tube (b) (^ inch diameter), fitting air- 

 tight into a retort (c) so deep that the end thereof should 

 be below the aperture of the retort-stem. With the ex- 

 tremity of the retort- stem was connected another bent 

 glass tube, dipping into the pneumatic trough, over which 

 was ajar of 340 cub. cent, capacity, to collect the gaseous 

 products evolved. The iron tube was placed in a " GrifnVs 

 gas-furnace," where it was raised to a bright red heat, in 

 some parts approaching to whiteness. When the iron 

 tube was red hot, the naphthalin was distilled through 

 cautiously. As soon as it made its appearance in the tube 

 SER. III. vol. v. c 



