ON ISOMERIC NAPHTHALENE DERIVATIVES. 383 



We have iu a previous report directed attention to the fact that the 

 polysulphonic acids which can be obtained by sulphonation are of certain 

 types, and that there is, in fact, an invincible objection on the part of two 

 SO3H groups — under conditions thereby prevailing — to remain in either 

 contiguous, or para-, or peri-positions. During the year we have been 

 able to examine three of the naphthalenedisulphonic acids which cannot 

 be obtained by direct sulphonation, i.e., the 1 : 2, 1 : 4, and 1 : 1' acids, 

 having prepared these, and the 2:3: 2'-naphthalenetrisulphonic acid by 

 an indirect method communicated to us by Dr. Duisberg.' With the aid 

 of these acids and of others prepared by the same method we hope to 

 further elucidate the phenomena of sulphonation. 



We have ascertained that of the three acids prepared by sulphonating 

 chloro-/3-naphthylamine hydrochloride, viz, — 



CI CI CI 



/\/\ NTT /\/\ XR S /\/\ 



NH., S / ^r > NH, 



s 



No. 1. No. 2. No. 3. 



Nos. 2 and 3 are of independent origin ; in other words, that, although 

 both can be obtained from No. 1, No. 2 is not convertible into No. 3 

 under the conditions which admit of the conversion of No. 1 into Nos. 2 

 and 3. It is noteworthy that, in the formation of the No. 2 and No. 3 

 acids, chloronaphthylaminedisulphonic acids always accompany the two 

 monosulphonic acids, and the investigation of these compounds, so far as 

 it has progressed, affords further evidence in favour of our view of the 

 complexity of the phenomena underlying the formation of /3-sulphonic 

 acids. 2 



Another case which may be referred to is that of the formation of 1 : 2 

 a-naphthylamine /3-sulphonic acid from naphthionic acid (1 : 4), which is 

 effected by heating the sodium salt of the latter at about 200°. It appears 

 probable to ns that the change involves the formation of a disulphonic 

 acid, which then undergoes hydrolysis, yielding the ortho-acid, thus : — 



NHj NH, NH., 



\/\/ 



\/\/ 



s s 



The production of disulphonic acid may be the outcome either of 

 direct intei'action of two molecules of the monosulphonic acid or of the 

 action of acid sulphate formed by the agency of traces of water unavoidably 

 present in the salt. It has actually been observed that hj'drated potassium 

 1:2:4 a-naphtholdisulphonate yields the ortho-mono-sulphonate when 

 heated.^ The superior stability of the ortho- as compared with the para- 

 sulphonate thus brought into evidence in the case of both naphthol and 

 naphthylamine is highly remarkable, bearing in mind the extreme in- 

 stability of the corresponding benzene derivatives, and is evidence that the 



' Cf. Chem. Soc. Proc, 1893, p. 166. 



"^ Ibid., 1890, p. 133. 



' Cf. Conrad and Fischer, Liebig's Annalen. 



