300 THE REVIVAL OF INORGANIC CHEMISTRY. 



relations of the elements, which are based not on theory, bnt on obser- 

 vation pure and simple, and it is on these, and not on the atomic 

 theory, that the Periodic Law is based. 



The Periodic Law is exerting a stimulating influence on inorganic 

 chemistry in various ways. It is leading to a more careful study of 

 all the elements, with the object of discovering further analogies; new 

 compounds are being prepared and old ones studied better witli this 

 in view; new kinds of periodicity are being sought for in physical as 

 well as in chemical properties. The question of the nature of the rare 

 earth metals, the asteroids of the elementary system, as Orookes calls 

 them, is being attacked with greater energy. Are these, of which 

 Crookes claims there are thirty or perhaps sixty, capable of being 

 fitted into the system as it now exists? Must we modify it in order 

 to take them in, or do they represent certain exceptional phases 

 of the evolution of matter from the original protyl, or different very 

 stable modifications on allotropic forms of a few elements? Do 

 the blanks within the system represent existing but as yet undis- 

 covered elements? Do some of them correspond to hypothetical 

 elements, which for some unknown reason are incapable of existence, 

 like many organic compounds which are theoretically possible, but 

 which, if momentarily existing, lapse at once into other forms, or must 

 the scheme be so modified as to exclude them? These are some of the 

 questions raised by the Periodic Law which it belongs to the inorganic 

 chemist to solve. Most important of all is the question of the cause of 

 the periodicity. Before we can hope to establish a mathematical and 

 possibly a genetic relation between a series of numbers, such as the 

 atomic weights and the chemical properties of the elements, we must 

 establish with greater accuracy than heretoi'oie the precise magnitude 

 of these numbers; and it is this that an ever increasing number of 

 atomic- weight chemists is striving to do. The question of the unity 

 of matter is one to a solution of which we are no nearer than ever, and 

 the Peroidic Law in its present form does not afford a proof, or, I 

 think, even a presumption in favor of a genetic relation between the 

 elements. It is quite conceivable that we may have relations of prop- 

 erties without a common origin. With ever increasing accuracy we 

 seem to be removing further and further from the possibility of any 

 hypothesis like that of Prout. The electric furnace, with its tempera- 

 ture of 3,500° C, gives not a sign of the decomposition or transforma- 

 tion of the elements. • These questions and the query why we know 

 no elements below hydrogen or above uranium, why the number of 

 the elements is limited, and why there are not as many kinds of matter 

 as there are different wave-lengths of light — all these seem to belong 

 as yet to a scientific dreamland rather than to the realm of legitimate 

 research, yet their solution, if possible at all, will be accomplished 

 only by the labors of the inorganic chemist. 



Let us now turn to the more special consideration of the questions of 



