ON THE ELECTROLYTIC METHODS OF QUANTITATIVE ANALYSIS. 311 



seems on the whole preferable for ordinary simple determinations. The 

 further investigation of other methods will be conducted more from the 

 point of view of their application to special cases, such as separations. 



The tabulated experiments given in this paper are only a small portion 

 of those obtained, as experiments were often repeated under similar or 

 slightly varying conditions, so that general opinions might be more con- 

 fidently formed. In the case of cobalt especially the total number of 

 experiments was considei-able, owing to the much greater difficulty of 

 obtaining deposits which were really satisfactory. The selection has not 

 been made so as simply to give a series of the most concordant results, 

 but may be taken as fairly representative. 



In conclusion, I have to express my indebtedness to my brother, Mr. 

 Ralph Marshall, for assistance in carrying out the routine work of 

 numerous experiments during the latter part of the investigation. 



Isomeric Naphthalene Derivatives. — Report of the Committee, consisting 

 of Professor W. A. Tilden {Chairman) and Dr. H. E. Arm- 

 strong (Secretanj). 



Although it is established that when betanaphthol is acted on by bromine, 

 at first bromine enters the hydroxylated nucleus in position 1, and in the 

 second place the non-hydroxylated ring in position 3', the structure of 

 tribromonaphthol remains undetermined ; but it is certain that the third 

 bromine atom is introduced either into position 3 or into position 4, as 

 both these are occupied in tetrabromonaphthol. 



Considerable difficulty has been experienced in settling this point. 

 Meanwhile, in extending the inquiry, in order to obtain complete infor- 

 mation of the influence on substitution exercised by the OH group in 

 betanaphtnol, the discovery has been made that the two possible homo- 

 nucleal forms of tribromonaphthol are both produced when betanaphthol 

 is acted upon by three molecular proportions of bromine. The crude 

 product cannot be directly purified, but by converting it into acetate and 

 repeatedly extracting this with boiling acetone, about half is dissolved ; 

 the residue almost entirely consists of the acetate, of the tribromobeta- 

 naphthol already described by Armstrong and Rossiter. A further 

 quantity of this acetate is obtained by fractionally crystallising the solu- 

 tion, and also about 15 to 20 per cent, of the acetate of a new tribromo- 

 betanaphthol. AltJiough the two isomerides resemble each other very 

 closely, and cannot be directly separated, their derivatives differ consider- 

 ably ; thus — 



A. and R. New 



o o 



Tribromobetanaphthol m.p. 15.5 159 



„ „ acetate , 184 149 



„ „ benzoate ....,, 187 164 



Nitrodibromobetanapbthol ., 156 163 



Dibromobetanaphthaquinone ,,150 187 



The comparative investigation of the dibromonaphthoquinones ob- 

 tained from the tribromonaphthols and other sources is being undertaken 

 with the object of determining their constitution and that of the naphthol 

 derivatives from which they are prepared. That melting at 171°, obtained 



