seriously supposed that calcium had been decomposed, because the green line of its spectrum had been made to disappear by fractioned precipitations 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 surprising 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 supposition 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 element, 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 differences whatever. Béla 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 fractions from active uranium compounds; on the other hand they succeeded 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 anhydrous 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 Béla 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.
