224 SCIENCE PROGRESS 



isomeric changes take place is probably to be attributed to the 

 greater readiness with which an electrolyte can discharge at 

 two points in the same molecule as compared with interactions 

 in which the products of electrolysis have to be delivered to 

 different molecules ; the larger number of units that have to be 

 brought into the electrolytic circuit in the latter case provides 

 an ample explanation, from the kinetic standpoint, of the 

 lessened efficiency of the various agents employed. A chloro- 

 amine is thus a better agent for chlorinating the ring-system 

 of its own molecule than it would be for acting upon some 

 other substance, and similar considerations apply even more 

 emphatically in the case of the nitro group. 



(d) Transference of Hydroxy I Groups and of Double Linkages. — 

 The interconversion of alcohols and olefines has been so fully 

 dealt with in a previous article x that only a brief reference need 

 be made to it at this point. The mechanism of the change 

 depends on the dissociation of the alcohol (or its sulphate) into 

 olefine and water (or sulphuric acid). These operations may 

 be formulated electrolytically, the addition to the olefine of 

 water or of sulphuric acid depending on the discharge at the 

 double bond of the radicles H and OH or H and S0 4 H, whilst 

 the dissociation of the alcohol or its sulphate depends on an 

 electrolysis in the reverse direction. Attention may, however, 

 be directed to the dominant importance of this machinery in 

 determining the plastic character of the members of the terpene 

 group of compounds. These substances possess the faculty of 

 undergoing isomeric change to such an extraordinary degree 

 that in some cases, and notably in that of pinene, it is the 

 exception rather than the rule to be able to prepare derivatives 

 which possess the same structure as the parent substance. In 

 nearly every case these changes can be explained by the 

 addition and removal of water, sulphuric acid or hydrogen 

 chloride, sometimes in connection with the ethenoid linkages 

 of the molecule, and sometimes in connection with the ring- 

 systems. Examples might be multiplied to almost any extent, 

 but it will suffice to mention the conversion of limonene and 

 of terpinolene into terpinene as illustrating the migration of a 

 double bond under the influence of an acid catalyst by a series 

 of changes precisely similar to those studied by Butlerow in 

 the isodibutylenes : 



1 Lowry, " Isomeric Change, Part I.," Science Progress, 1909, iii. 616-37. 



