74 • report — 1884. 



stating experimental facts which admit of no dispute. These tables 

 bring prominently forward the fact that those names have endured which 

 express no particular opinion on the ultimate constitution of the bodies 

 to which they were applied. Where the names have expressed such 

 opinions the ndvance of knowledge has necessitated change. Sixty 

 years ago the names ' Bi-chloride of phosphorus ' and ' Perchloride of 

 phosphorus ' were both applied to the higher chloride of phosphorus. 

 The former name has not lasted because it expressed a particular view 

 as to the number of atoms in the molecule, which view is no longer 

 accepted. The other name has endured because it merely expressed the 

 experimental fact that the compound contained more chlorine than the 

 lower chloride. To secure permanence for the future this principle 

 should be acted on. As a general rule those names are to be preferred 

 which have shown the most vitality and have led to no ambiguity. 

 Where there are hvo compounds composed of the same elements the terminations 

 OUS and ic should be employed. These terminations have been used in the 

 same sense by the great majority of chemists since Lavoisier. The 

 terms 'cuprous chloride,' ' chlorure cuivreux,' ' Kupferchloriir ' for the 

 lower chloride of copper, and the terms ' cupric chloride,' ' chloimre 

 cuivrique,' ' Kupferchlorid ' for the higher chloride have been used by 

 English, French, and German chemists consistently and without ambiguity. 



The prefixes proto, deuto, &c, introduced into chemical nomenclature 

 by Thomas Thomson, were not intended by him to indicate the number 

 of atoms in a molecule, but to mark the first, second, or third compound 

 of a series. Thus he styled the lower and higher chlorides of copper 

 ' protochloride ' and ' deutochloride ' respectively; but other chemists 

 have styled the higher chloride the protochloride, thereby indicating that 

 the molecule contained one atom of copper, and the lower chloride the 

 dichlori.de, thereby indicating that the molecule contained two atoms of 

 copper. Where the prefixes proto, deuto, &c, are retained they should 

 always be applied in the sense used by Thomson as indicating the first, 

 second, &c, compound of a series. 



A name once given to a particular body should not be taken from 

 that body and applied to another without the gravest reasons for the 

 transfer — reasons accepted by the majority of chemists. The name 

 carbonic oxide has been regularly used to denote the lower oxide of 

 carbon from the time of its discovery. Until quite recently, the name 

 ' carbonic oxide ' served without ambiguity to indicate a particular 

 compound. This name has lately been applied by certain chemists to the 

 higher oxide of carbon, and a new name has been given to the lower 

 oxide. On account of this transfer the name has become ambiguous. 

 A return to the common nomenclature would involve less change, and 

 would, therefore, be preferable to the adoption of two new names to avoid 

 this ambiguity. 



Report of the Committee, consisting of Professor W. A. Tilden and 

 Professor H. E. Armstrong (Secretary), appointed for the purpose 

 of investigating Isomeric Naphthalene Derivatives. 



Tiie Committee have to report that some steps have been taken towards 

 commencing the work ; but, owing to the unfortunate fire at the London 

 Institution, whereby much of the material was destroyed, and the appoint- 

 ment of Dr. Armstrong to the Chair of Chemistry at the Central Technical 

 Institute, the results are not yet in a state fit for publication. 



