174 REPORT — 1889. 



Eecent experiments of Mr. Houlding (cf. ' Chem. Soc. Proceedings,' 1889, 

 74) have served to show that the minor product is not the 2 : 3' derivative. 

 Subsequently Mr. Wynne and I have found (ibid. 18S9, 119) that the 

 chief product of sulphonation in the case of/3-iodonaphthalene corresponds 

 with the chief product afforded by y8-chloro- and yS-bromonaphthalene, and 

 that the minor product obtained from /3-iodonaphthalene is the second 

 heteronucleal 2 : 4' aZp/ia-sulphonic acid : so that whereas only one 

 alpha-acid is obtained on sulphonating ^-chloro- and yS-bromonaphthalene, 

 /3-iodonaphthalene yields the two possible heteronucleal alpha-acids. Both 

 jS-iodo a-sulphonic acids, however, are found to yield the same 2 : 3' 

 /3-sulphonic acid when heated at about 150°. It is therefore not 

 improbable that on sulphonating the chloro- and bromo- compounds, two 

 aZp7ia-acids are initially formed, and that one of these forth with under- 

 goes spontaneous isomeric change into the 2 : 3' acid. 



The results obtained in the case of the dichloronaphthalenes tend to 

 support this view. Thus 1:3 {9) dichloronaphthalene affords but a 

 single sulphonic acid ; this product is identical with that prepared by 

 Widman from naphthalene-a-sulphonic acid and is in all probability the 

 1:3:4' acid. 



1 : 2 dichloronaphthalene, however, yields two isomeric acids, the 

 chief product (about 2-3rds) being the 1:2:4' (a) acid, the subsidiary 

 product the 1:2:3' (/3) acid ; as the latter is almost the sole product if 

 the original product of sulphonation be heated at 150°-160° during several 

 hours, it is probable that the ;S-acid in the original product is formed by 

 spontaneous isomeric change at the moment of sulphonation. 



1 : 4 (/3) dichloronaphthalene, however, yields as sole product the 

 1:4:2' {(3) sulphonic acid, and it would appear that isomeric change 

 takes place in this case spontaneously and with exceptional facility and 

 completeness. 



1 : 4' (y) dichloronaphthalene yields as chief product (about four- 

 :fifths), the 1 : 4' : 2' betasulphonic acid (m.p. of sulphochloride 139°- 

 140°), together with what appears to be the isomeric 1 : 4' : 3' beta-acid 

 (m.p. of sulphochloride 98°-100°) ; in this case it is possible that an 

 alpha acid is first formed, which at once changes, but more probably the 

 two alpha positions are ' protected ' by the two alpha-chlorine atoms, the 

 1 : 4' : 3' beta acid being first formed, and at once partly converted by 

 spontaneous isomeric change into the more stable 1 : 4' ; 2' acid. It is 

 obvious that much important information is to be obtained by further 

 study of the subject. 



Azo-dye stuffs derived from naphthalene.- — In the second of these reports 

 it was argued that the azo-dye stuffs from betanaphthol were all 1 : 2 

 a-/3 derivatives, and as a matter of course the argument would apply 

 equally to betannphthylamine. Experiments were commenced with the 

 object of obtaining the data required to verify this theory, but their 

 continuance became unnecessary in consequence of the publication of a 

 valuable paper by Dr. O. N. Witt ('Berichte,' 1888, 34-68), in which it 

 is demonstrated that the azo-colours from the free isomeric betanaphthyl- 

 aminesulphonic acids and a number of others are all 1 : 2 derivatives. 

 In pointing out (cf. second report) that the formation of the azo-colour 

 involves an isomeric change which apparently can take place only in the 

 one direction, and that on this account it is impossible to effect the 

 introduction of the azo-group into any other position than that con- 

 iiguous to the OH or NHj group, no special note was taken of the 



