570 REPORT— 1902. 



never really want such conceptions ; one of the many definitions of science is the 

 quantification of phenomena, and in every chemical phenomenon the substances 

 concerned are quantified as molecules. The quantification of radicals expressed 

 by the atom is fundamentally the same in jirinciple as that of substances, namely, 

 that of chemical equality in interaction ; but it may be better to say that it is 

 dependent upon the quantification of substances as molecules. 



In the interaction of double decomposition each substance by contact and 

 union with the other develops and manifests a dual character by becoming 

 distributed as the two new substances, with the consequence that each of these 

 has certain properties the same as those of the one, and certain others the same 

 as those of the second interacting substance. What is common in this way to 

 one of the interacting and one of the resulting substances is a radical of these 

 substances, of which there are evidently four in every double decomposition. 

 These radicals of a single interaction are defined as whatever two parts of the 

 powers of a substance to yield the simple substances of its chemical composition 

 are, in certain interactions, continued separately from each other in the two new 

 substances. But the pair of radicals developed in the various double decomposi- 

 tions of a substance being by no means always the same, one of the radicals 

 of one pair must include in its composition part or all of one of those of another 

 pair. Acetic acid has for one pair of radicals methyl and carboxyl, and for 

 another pair acetyl and hydroxyl. Of these, carboxyl includes hydroxyl, and 

 acetyl includes methyl. Again, acetic acid yields the hydrogen and acetate 

 radicals in one interaction, and hydroxyl and acetyl in another, so that in these 

 cases the acetate radical includes acetyl and the hydroxyl includes the radical 

 hydrogen. Now, what is common to carboxyl and acetyl and what is common 

 to the acetate radical and hydroxyl are also treated as radicals, the one being 

 known as carbonyl and the other as the radical oxygen. These are examples 

 of what may be distinguished from the others as the polyvalent radicals. They 

 are radicals of radicals, and therefore also radicals of substances. They may be 

 defined as the common part of two or more other radicals. A single deiinition of 

 all radicals can be given, but it is not instructive. A radical is any single power 

 or any interdependent association of the powers of a substance to produce simple 

 substances which continue in any product or series of successive products of its 

 chemical change. 



Before I leave the subject of the radical I wish to repeat that it is only 

 when it is interacting that a substance shows a dual character or division, as it 

 were, into parts or radicals, and that the duality it then shows is determined as 

 much by the nature of the other substance as by its own. A substance is neither 

 actually nor conceptually the sum of its radicals. The very fact of the difierence 

 of these in ditfereut interactions should be proof of this ; though it only leads 

 to its being taken to be at least the sum of its ultimate or simple radicals. 

 If, however, it is not the sum of its proximate radicals, it is hard to see how it 

 can be imagined to be that of the ultimate ones. In relation to its radicals, a 

 substance must be held to present itself as any one of these for the purpose of 

 investigation, and at the standpoint from which it is considered. It is then to the 

 mind that particular radical, though also something else; just as snow is white 

 and cold, yet also something else, for the moment unconsidered. Nor can the 

 two products of an interaction be looked upon as themselves the sum in properties 

 of the interacting substances. To a limited extent and imperfectly, we can attach 

 to a given radical certain of the properties common to its compounds ; but it 

 needs no greater insight than we have already, to recognise that a substance cannot 

 be what it is in one way, without being in that way greatly aflected by what 

 it is in another. This is now a recognised but not sufiiciently considered point, 

 and I therefore welcome those publications of Professor Vorlaender, of Halle (who 

 now honours this Section with his presence), in which he has been vigorously 

 calling attention to the extent to which the properties of a substance, acid, basic, 

 stable, and what not, depend as much as, if not more, upon the interrelations of 

 the radicals than upon the radicals themselves. 



One other thing J have to say about the radical, which ie as to the spelling of 



