a mon- 



on the Physical Properties of Compounds. 189 



an attempt to refer the fluorescent phenomena of the anthra- 

 cene series to the chemical constitution of the members of this 

 series. According to him, those derivatives fluoresce in which 



the two carbon groups binding together the two benzene rings 



possess the constitution C 6 H 4 |^ C 6 H 4 (where M 



atomic element or group) ; whilst those derivatives which contain 



the double ketone group C 6 H^ c ^C 6 H 4 , or the group corre- 



fYOHVC H-") 

 sponding to it in phenulanth'acene,C 6 'K i <^QQ__ ^C 6 H 4 , 



do not fluoresce. This rule he finds to hold good in the case 

 of all the 60 to 70 compounds to which it can at present be 

 applied ; thus: — 



Fluorescent . 



Anthracene C 6 H 4 ^ H \C 6 H 4 . 



CH 



Dichloranthracene CeHaCl/^NCeHgOl. 



Trichloranthracene Xi\i /X*. 



CH 



Dibromanthracene „ 



Tetrachloranthracene „ 



Anthracene sulphonic acid ... C 6 H 4 <^i M] 6 H 3 .S0 3 H. 



CH 

 /CFT\ 

 a-anthracene disulphonic acid X lx | /X*. 



CH 

 /3-anthracene disulphonic acid „ 



&c. &c. 



Non-fluorescent. 



CO 

 Anthraquinone C 6 H 4 /qq\C 6 H 4 . 



CO 

 Anthraquinone sulphonic acid ... C 6 H 4 /qq^>C 6 H 3 .S0 3 H. 



CO 

 Oxyanthraquinone C 6 H 4 /q q\C 6 H 3 . OH. 



Alizarine C 6 H 3 .OH<qq>C 6 H 3 .OH. 



&c. 

 * Constitution of X and X x unknown. 



