267 



SO,NH., m. p. = 216°. 



The establishment of the existence of such a series of ten isomeride.s 

 formed by the introduction of but two atoms of chlorine into a hydro- 

 carbon is in itself remarkable ; it is still more remarkable when the 

 diversity of properties which the isomerides manifest is taken into con- 

 sideration ; moreover the identification of ten isomerides and the recog- 

 nition of their constitution afford striking testimony to the completeness 

 of modern methods of inquiry and the truth of our theory of constitution : 

 however much our symbols may differ from actuality, there cannot be a 

 doubt that they afford a most accurate presentment of intramolecular 

 relationship. 



It may be added that the facts now established place it beyond ques- 

 tion that the hydrocarbon naphthalene has a symmetrical structure such 

 as is indicated by the conventional double hexagon formula ; it remains 

 to solve the far more difficult problem involved in the determination of 

 its exact inner structure. 



The opportunity afforded by a series of ten isomerides for the com- 

 parative study of physical properties in their relation to constitution is 

 obviously very great, and it is intended ere long to enter on this branch 

 of the inquiry. 



The isomeric dihromonaphtJialenes. — With the object of securing the 

 data necessary for the exact comparison of the chloro- and bromo-deriva- 

 tives of naphthalene, and especially the behaviour of naphthalene towards 

 chlorine and bromine, much time has been devoted by the writer and Mr. 

 Rossiter to the study of the dibromonaphthalenes. The results are not 

 yet sufficiently complete to render their publication desirable. 



The isomeric trichloronaphthale^ies. — Theoretically fourteen isomeric 

 trichloronaphthalenes can exist. As the determination of the constitu- 

 tion of a large number of naphthalene derivatives — including many of 

 technical importance — is dependent on a knowledge of the trichloronaph- 

 thalenes, Mr. Wynne and the writer have paid much attention to their 

 study ; besides the seven already known, they have succeeded in preparing 

 six others, and are at present endeavouring to prepare the only modifica- 

 tion which remains to be discovered. The melting points of the thirteen 

 known trichloronaphthalenes and their probable constitution are indicated 

 in the following table, in which also are given the letters by which they 

 have been distinguished. 



