RADIOACTIVITY AND MATTER. 269 



seriously supposed that calcium had been decomposed, because the green 

 line of its spectrum had been made to disappear by fractioned precipita- 

 tions of its chloride, and crystallographers on this ground tried to find 

 reason for the extraordinary richness of the crystal forms of calcite. 

 Similar pardonable errors may also occur in other cases, though we do 

 not mean to assert that such errors have actually been committed in 

 the fractioning of radioactive substances. 



But we must be permitted to ask whether it is really justifiable to 

 assume the presence of a new element in a substance for the sole 

 reason that this substance is radioactive. It would certainly be sur- 

 prising if every one of the numerous, long known chemical elements, 

 which show radioactivity, were to contain also an elementary associate 

 of almost exactly the same chemical character. Against such a sup- 

 position we can mention many reasons, entirely independent of the 

 fact that such a supposition is in conflict with all general experience 

 and the hitherto unshaken idea of the nature of chemical elements. 

 Uranium — one of the elements in question — is certainly a typical ele- 

 ment, yet, according to William Crookes, it can be separated into an 

 active and a non-active fraction by merely treating its hydrous nitrate 

 with ether, or by fractional crystallization or by fractional ignition — 

 and at the same time these fractions are said to show no chemical dif- 

 ferences whatever. Bela v. Lengyel who doubts the existence of 

 radium, succeeded in making barium active by heating its nitrate with 

 uranylnitrate, and Henry Becquerel prepared a strongly active barium 

 sulphate by precipitating by sulphuric acid a barium chloride solution 

 to winch uranyl chloride had previously been added; in this case the 

 activity of the uranium compound had at the same time diminished. 

 Further K. A. Hofmann and E. Strauss have obtained inactive frac- 

 tions from active uranium compounds; on the other hand they suc- 

 ceeded in temporarily withdrawing from uranium its activity by means 

 of barium or bismuth compounds. Especially remarkable are the 

 experiments of A. Debierne, which have been conducted in a similar 

 manner with actinium, and by which it was proved that it is easy to 

 make active the compounds of barium so that they scarcely differ from 

 those of radium, except that they do not give a radium spectrum. The 

 active barium is said to stand between barium and radium, its an- 

 hydrous chloride is self-luminous like that of radium, and may equally 

 well, by fractional crystallization, be separated in a more active and a 

 less active portion. 



By induction alone such remarkable phenomena can hardly be 

 accounted for. The objection raised by F. Giesel against Bela v. 

 Lengyel, namely that the activation of barium first produced by the 

 latter might be due to some radium contained in the uranium salt used, 

 is disproved by the fact stated, that under other conditions the same 

 result even in a much higher degree was obtained. 



