234 



REPORT 1887. 



product is obtained, consisting chiefly of an acid which most probably is 

 the ethylated derivative of Bayer's naphtholsulphonic acid together with a 

 small proportion of what is undoubtedly the isomeric ethylated derivative 

 of Schaefer's acid ; if, however, the product be heated on the water-bath, 

 the former acid is converted into the latter. 



These results afford evidence of a most interesting character, both the 

 ease with which the conversion is effected and the variety of isomeric 

 changes which are disclosed being remarkable. Special attention is being 

 directed to the further elucidation of this branch of the inquiry. 



Theory of the formation of azo-dye stuffs from /3-naphthol. — A series of 

 dye stufl's of considerable technical value are produced from y8-naphthol 

 and its sulphouic acids by interaction with diazo-salts. It is well known 

 that in the case of yS-naphthol itself the a-hydrogen atom contiguous to 

 the OH group becomes displaced by the azo-group. This position 

 appears to be free in all the sulphonic acids which afford azo-colours, and 

 those naphthol derivatives in which it is not free appear to be incapable 

 of forming such colours ; it is therefore a legitimate inference that all 

 azo-dyes derived from /3-naphthol are formed by the introduction of an 

 azo-group in the position indicated. The formation of such azo-colours 

 in all probability involves the occurrence of isomeric change, the initial 

 action consisting in the displacement of the H atom of the OH group by 

 the azo-group Az, the compound thus constituted then undergoing 

 change ; thus — 



H Az 



OAz 



In the case of such compounds the isomeric change apparently can 

 take place only in the one direction, and on this account it is impossible 

 to effect the introduction of the azo-group into any other position ; if it 

 were possible to displace some other hydrogen atom, azo-colours might 

 well result. 



Melting-points of the isomeric sulpho- chlorides. — The following num- 

 bers are interesting, as showing that the same change in composition 

 does not always involve a change in physical properties of the same 

 order; it will be noticed that, whereas in the 1:4 series the bromo-com- 

 pound has a lower melting-point ' than either the cbloro- or iodo-com pound, 

 in the 2:3 series the bromo- derivative has the highest melting-point; the 

 low melting point of the 2:3' iodosulphochloride is also remarkable. 



a-Cl.CioHc.SOoCl 

 a-Br.C,oHo.SO.>Cl 

 a-I.C,oHr,.SO,Cl 



/S-CI.OioHc.SO^Cl 

 ^-Br.C.oHg.SO^Cl 

 ^-LC.oHg.SO^Cl 



' The melting-point cited is that given by Jolin ; the others are from my own 

 observation. 



