Marcu 17, 1904] 
LETTERS TO THE EDITOR. 
(The Editor does not hold himself responsible for opinions 
expressed by his correspondents. Neither can he undertake 
to return, or to correspond with the writers of, rejected 
manuscripts intended for this or any other part of NatTuRE. 
No notice is taken of anonymous communications. ] 
Radio-tellurium. 
In an article in the issue of Nature for February 11 Mr. | 
F. Soddy gave some account of certain of the results of my 
investigations with regard to radio-tellurium. In this he 
criticised somewhat severely my choice of a name for the 
radio-active substance. He holds the substance investigated 
by me to be identical with polonium, and even goes farther 
than Madame Curie herself, who, in her recently published 
“* Dissertation,’’ characterises the use of a new name for 
the substance as premature. 
In a paper published by me in the Berichte der deutschen 
chemischen Gesellschaft in September last, I have already 
given the reasons which have induced me to propose the 
name radio-tellurium ‘‘ provisionally ’’ (vorlaufig). Mr. 
Soddy has not discussed these reasons, although he has had 
the opportunity of making himself acquainted with my com- 
munication before writing his criticism. As the question has 
once been raised before the readers of NAtuRE, however, it 
might be of advantage to discuss it here somewhat more 
fully. 
Shortly after the discovery of polonium by M. and Madame 
Curie, Giesel found that this substance quickly lost its radio- 
activity, and he characterised it therefore as inducedly active 
bismuth. P. and S. Curie themselves had, indeed, shortly 
before the publication of my first paper on the subject, de- 
fined polonium as ‘‘ une espéce de bismut actif.’’ The 
observations of Giesel and the Curies differ from one another 
on two points. Giesel’s polonium emitted a and B rays and 
lost its activity within a few weeks, while that of the Curies 
sent out, only a rays, and lost the greater part of its activity 
only after the lapse of a few months. More recently Giesel 
has shown that bismuth by prolonged immersion in a solu- 
tion of pure radium bromide can become permanently (?) 
active, and then emits only a rays. 
Hence there exists with certainty an inducedly active 
bismuth giving out only @ rays, and this might with 
accuracy be called polonium. There exists, further, a 
bismuth giving out a and B rays—Giesel’s polonium. In 
this I have found traces of radio-tellurium, and I have shown 
that after the removal of the latter the remaining substance 
shows strong 8 and diminished a radiations. Finally, after 
the discovery of radio-tellurium, Madame Curie has purified 
her polonium by fractional precipitation of the subnitrate, 
and has ultimately arrived at a substance, of which she de- 
scribes precipitates, the properties of which agree neither 
with those of bismuth nor with those of radio-tellurium. 
This substance she calls polonium. It can be seen from this 
brief summary that the idea associated with the name 
polonium is an extremely variable and indeterminate one. 
In the investigation of bismuth separated from Joachims- 
thal pitchblende in an essentially different way from 
Madame Curie,’ I found a small quantity of tellurium 
which was extraordinarily active. From one kilogram of 
bismuth I was able to separate only about a tenth of a 
gram of tellurium. This had not previously been found in 
the pitchblende. 
Since the substance was distinguished from ordinary 
tellurium at first only by its radio-activity, I named it radio- 
tellurium “‘ provisionally.’’ To give a final name to it 
seemed to me to be premature. The example of polonium 
showed clearly enough the confusion arising from giving 
a permanent name to a thing before the thing itself has 
been accurately defined. Hence Madame Curie can least of 
all afford to reproach me with being too hasty in my 
naming. 
The further investigation of radio-tellurium showed how 
necessary was my caution, for it proved that the substance 
consisted mainly of ordinary tellurium. It was possible, 
however, to separate, in a quantity amounting at most to 
1 Madame Corie has recently published her method of separation. I 
separated the bismuth from the pitchblende by precipitating it as oxy- 
chloride by the addition of much water to the hydrochloric acid solution. 
NO. 1794, VOL. 69] 
NATURE 
461 
a few tenths of 1 per cent., a radio-active substance of 
extremely high activity in proportion to its quantity. This 
substance, of which up to the present I possess only a few 
milligrams, I have named radio-tellurium ‘‘ provisionally.’’ 
Ought I, as Mr. Soddy seems to suggest, to call it also 
polonium, and so increase the present confusion? 
Mr. Soddy appears to wish the justification for a new 
| name to depend on the proof of the constancy of radio-activity 
of my substance. This suggestion of Mr. Soddy’s was not 
necessary to induce me to pursue experiments in this direc- 
tion. Such are already undertaken in the most accurate 
manner, but their results, which must be waited for, have 
not the least to do with the question of nomenclature. The 
name polonium does not denote a particular substance which 
has the property of losing its radio-activity with the course 
of time—who could at present be sure of the constancy of 
activity of radium?—but merely radio-active bismuth. So 
far as the constancy of the radio-tellurium emission is con- 
cerned, I may here cite the following experiment. A copper 
plate of about 8 square ‘em. surface, on which not more 
than a few hundredths of a milligram of the purest radio- 
tellurium have been precipitated, now, after nine months, 
radiates so powerfully that the phosphorescence of zinc 
blende and of barium platinocyanide can be made visible to 
an audience of several hundred people. 
Mr. Soddy has thought fit towards the close of his article 
to attribute to certain German organic chemists the custom 
of ‘‘ rechristening well-known bodies.’? In a way that can 
hardly be misunderstood, he insinuates that this may be 
traced to an endeavour to claim for themselves the dis- 
coveries of others. 
This somewhat objectionable charge Mr. Soddy has in no 
way shown to be grounded. Polonium can, indeed, hardly 
be reckoned as one of the well-known bodies. 
I can also the more easily refrain from answering this 
aspersion as I am aware that some of the most prominent 
English chemists have a quite different opinion of their 
German colleagues from that of Mr. Soddy. I would re- 
commend in this direction a perusal of Prof. P. F. Frank- 
land’s address to the chemical section of the British 
Association in 1gor. W. MarcKwatp. 
Pror. Marckwatp’s communication will probably be 
welcomed by the scientific world on account of the oppor- 
tunity it affords of settling finally the disputed question as 
to the nature of the body named by him ‘‘ radio-tellurium.’’ 
In my own mind, before I had read Prof. Marckwald’s 
letter, a doubt still lingered as to the identity of the body 
with Madame Curie’s polonium on account of the very de- 
finite statement made by Prof. Marckwald in his first com- 
munication on the subject that the activity of his body did 
not decay with the time. This to me was an insuperable 
difficulty in the way of considering the two bodies to be 
identical. The other reasons Prof. Marckwald has 
advanced—and it is not likely I should have ventured to 
express an opinion without having made myself acquainted 
with these reasons—seemed to arise out of a misconception 
on the part of Prof. Marckwald himself as to the nature of 
polonium. This point I hope to discuss later, but first I 
wish to deal with the, to me, important question of the 
constancy of the radio-activity of radio-tellurium. It is 
satisfactory to learn that accurate determinations are in 
progress. Everyone will understand that the results must 
be waited for. What I did not appreciate before reading 
Prof. Marckwald’s letter was that his conclusion that the 
activity of radio-tellurium did not decay with time was 
merely an impression unsupported by actual measurements. 
The experiment quoted, that a sample of radio-tellurium 
after nine months still illuminates a phosphorescent 
screen brightly, would seem to illustrate my _ point 
that Prof. Marckwald even now seems to be under 
a misapprehension as to the nature of polonium. 
After nine months, polonium, according to the work of its 
discoverer, would still possess at least one-half of its initiat 
activity. I suppose no one would maintain that it is possible 
to remember over a period of nine months the various 
degrees of luminosity, produced by a radio-active prepar- 
ation, with sufficient accuracy to be sure of a diminution by 
one-half of the initial luminosity during that interval. In 
| two or three years the decay of activity of polonium should 
