218 REPORT— 1886. 



Naphthalene-? -fi-disulphonic Acid. — This acid is prepared by acting on 

 naphfchalene-/3-mono3ulphonic acid with chlorosnlphonic acid, and is cer- 

 tainly the chief product, but it remains to ascertain whether an isomer is 

 not produced simultaneously. It is at once converted by the action of 

 bromine into a dibromo-ruonosulphonic acid ; this behaviour renders it 

 more than probable that the sulphonic radicle introduced by the agency 

 of the SO3HCI assumes an a- position. 



The two acids prepared by Bbert and Merz by the action of sulphuric 

 acid at a high temperature (160°-180°) are in all probability /3-/3-deriva- 

 tives ; they are both isomeric with the acids obtained by sulphonating- 

 naphthalene-a- and /3-7>io«osulphonic acids by means of SO3HCI : and 

 this difference being established between the action of sulphuric acid 

 and that of chlorosulphonic acid, it appeared desirable to ascertain the 

 behaviour with SO3HCI of the naphthalene derivatives which had pre- 

 viously been converted into sulphonic acids in the ordinary manner. The 

 derivatives taken were a-nitro-, a-bromo-, a-chloro-, and /3-chloro-naph- 

 thalene : these have all been found to yield the same products when 

 sulphonated by means of SO3HCI as on treatment with sulphuric acid. 

 It is especially noteworthy, however, that from both a-bromo- and 

 fi-chloro-naphthalene an acid has been obtained in small quantity isomeric 

 with the ^ara-sulphonic acid previously known, and which forms the 

 chief product ; this secondary product is probably also an a-o -derivative 

 like the primary product, but of the same series as the nitro-sulphonic 

 acid formulated above. Two isomeric sulphonic acids also are obtained 

 from /3-chloronaphthalene. One, which is the chief product when 

 SO3ECI is used, has been shown by Arnell to correspond to 0-dichloro- 

 naphthalene, while the other corresponds to t-dichloronaphthalene, and 

 therefore to the /3-disnlphonic acid of Bbert and Merz, and to Schaefer's 

 betanaphtholsulphonic acid. Probably 0-dichloronaphthalene is the 

 ortho- or 1-2 modification, and it may almost be regarded as established 

 that £-dichloronaphthalene is a /3^-/33'-derivative ; so that, while «- and 

 ^-chloronaphthalene both behave in the manner to be expected from the 

 analogy subsisting between benzene and naphthalene, evidence is afforded 

 by the production of the a'-a'^'-derivative from the one and of the iP-jo^'- 

 derivative from the other of the existence in the naphthalene molecule, in 

 addition to the ' para-plane ' of benzene, of two ' planes of symmetry,' as. 

 it were, in which an inflaence is exercised. 



The study of the action of bromine on aqueous solutions of the naph'- 

 thalene-sulphonic acids has also furnished results of interest. It has long 

 been known that when naphthalene-a-sulphonic acid is treated with 

 bromine the sulphonic group is displaced, dibromonaphthalenes being 

 formed, whereas the /J-sulpbonic acid is converted into a dibromonaph- 

 thalene- sulphonic acid, the SO3H group retaining its place. It now 

 appears that this behaviour of the two acids is fairly typical. Thus the- 

 two disulpbonic acids of Ebert and Merz — which are doubtless both /3-/3- 

 derivatives — yield isomeric dibromonaphthaquinonemowosulphonates on 

 treatment with bromine in excess — ^only one of the sulphonic radicles, 

 viz., that which is contained in the Cg groap which is oxidised, being 

 displaced. The isomeric dibromomonosulphonic acids obtained by 

 treating (a) naphthalene /3-monosulphonic acid and (h) the ?-/3-disul- 

 phonic acid above described with bromine are finally converted by the 

 action of bromine into the same tetrabromonaphthaquinone, the sulpho- 

 nic radicle being displaced, although in the /3-position, in consequence 



