252 

Letters to the Editor. 
[Zhe Editor does not hold himself responsible for 
opinions expressed by his correspondents. Neither 
can he undertake to return, nor to correspond with 
the writers of, rejected manuscripts intended for 
this or any other part of NATURE. No notice is 
taken of anonymous communications. | 
On the New Element Hafnium. 
THROUGH the courtesy of the editor of NATURE we 
have been able to see an advance proof of the letter 
of MM. Urbain and Dauvillier (NATURE, February 17, 
p. 218), and are glad to have the opportunity to add 
the following comment : 
Our main reasons for believing that the element 
celtium, the detection of which was announced by 
Urbain in ro1i, is altogether different from the 
element detected by us and named hafnium, are: 
1. Celtium and hafnium show very great differences 
in their chemical properties. While we have found 
no difficulty in purifying hafnium preparations from 
contents of rare earths, the separation of celtium from 
the rare earths was found by Urbain to be so difficult, 
that although the detection was announced in 1911, 
only samples of small concentration have been 
obtained up to the present time. 
2. It has not been possible by means of highly 
concentrated hafnium preparations to reproduce the 
characteristic optical spectrum ascribed by Urbain to 
celtium, and which, together with an investigation of 
the magnetic properties of his preparation, was the 
basis of the announcement of the discovery of this 
element. The result of a closer investigation of the 
optical spectrum of hafnium will soon be published. 
3. The X-ray spectrum of a preparation containing 
a percentage of an element high enough to measure 
magnetic properties should show the characteristic 
X-ray lines of this element in great intensity, altogether 
different from the exceedingly faint lines found by 
Dauvillier. Quite apart from the possibility of 
accounting for these lines as due to a higher order 
spectrum of other elements, it seems to be very un- 
likely that these lines should be due to a contamina- 
tion of Urbain’s preparation by a trace of hafnium. 
Not only as stated in our first letter (NATURE, 
January 20, p. 79) they do not coincide within the 
limit of experimental error with our measurements of 
the wave-lengths of the hafnium X-ray lines La, and 
Lg., but also the reason given by Dauvillier for not 
detecting the line Lg,, which is stronger than Lg,, can 
scarcely be maintained. In fact, our measurements 
for this line give a value which differs about 3 X- 
units from the Lu-line denoted by Dauvillier as Lg,’, 
and with the dispersion used it should be easily 
separated from the latter line. 
As stated in our letter in Nature of February 10, p. 
182, hafnium appears in large abundance in zirconium 
minerals, and we estimate the hafnium content of the 
earth’s crust to be more than one part in 100,000. In 
the meantime we had the highly interesting informa- 
tion from Prof. V. Goldschmidt in Christiania, that 
in an investigation of zirconium minerals, in collabora- 
tion with Dr. Thomassen, he has discovered a mineral 
in which hafnium is a main metallic constituent. 
This has been verified by an X-ray investigation in 
this Institute of a sample kindly sent to us by Prof. 
Goldschmidt. On the other hand, an investigation 
of certain preparations extracted from a titanium 
mineral from New Zealand and kindly sent to us by 
Dr. Scott did not reveal any hafnium line. Taking the 
sensitiveness of the method into account, this mineral 
canuot contain appreciable amounts of hafnium. 
The question discussed by MM. Urbain and Dau- 
villier which elements are to be ascribed in the family 
NO. 2782, VOL. I11] 
[FEBRUARY 24, 1923, 

NATURE 



of rare earths, has hitherto been.a matter of pure 
definition, The recent development of the theory of 
atomic structure, however, has given the question 
involved an entirely new aspect. The appearance of 
a group of elements in the 6th period in the periodic 
table exhibiting very similar chemical properties but 
quite different magnetic ones could be explained by 
Bohr on the basis of the fundamental principles of 
the quantum theory (for particulars cf. Bohr’s Nobel 
lecture, shortly to appear in Nature). For this 
atomic theory the properties of the elements in the 
6th period of the periodic table have therefore become 
of great importance. The stimulus to our present 
investigations was provided by the great difficulty of 
reconciling this theory with the results announced six 
months ago by Dauvillier and Urbain. In fact, the 
existence of an element with atomic number 72 and 
the chemical properties ascribed to celtium cannot be 
reconciled with the theory. Our confidence in the 
theory, however, has been amply justified. For by 
following up the theoretical deductions we have been 
led to detect a new element, which is the proper 
analogue of zirconium and with atomic number 72, 
present in considerable abundance in the earth’s 
crust. This confirmation of the theory was the 
deciding factor in our choice of the name hafnium 
for the new element. D. Coster. 
G, HEvEsy. 
Copenhagen, February 9. 

Hafnium and Titanium. 
Tue black iron sand from New Zealand examined 
by Dr. Scott in 1915 in which, as he informed the 
Chemical Society at its meeting on February 1, he 
found a substance which he is now inclined to regard 
as probably identical with an oxide of the new element 
recently discovered by Dr. Coster and Prof. Hevesy 
of Copenhagen, and named by them hafnium, was 
doubtless similar in character to the deposit observed 
to occur in the bed of a rivulet at Tregonwell Mill, near 
Menaccan, in the parish of St. Keverne, Cornwall, and 
also in a stream at Lenarth, in the same parish, and 
in which the Rev. William Gregor, the minister of that 
parish, who analysed the deposit in 1789, first detected 
the existence of the element now known as titanium. 
The Cornish mineral, a titaniferous iron sand of 
variable composition, was known mineralogically as 
menaccanite, and the new element was consequently 
termed menachin. Similar deposits occur in other 
parts of the world, and, in fact, are widely distributed. 
Their characteristic constituents are known variously 
as ilmenite, iserine, thuenite, hystatite, washingtonite, 
crichtonite, etc.; the results of analyses of them by 
Mosander, Marignac and Kobell are to be found in 
Greg and Lettsom’s ‘‘ Mineralogy,’’ and a list of 
localities in which they occur is given by Dana. 
Their composition is very variable, the amount of 
titanic acid, for example, ranging from 22:2 per cent. to 
46-9 per cent. They are all essentially iron titanates, 
associated with variable amounts of oxides ofiron, and, 
occasionally, of manganese and other substances. 
The name titanium was given to the element by 
Klaproth as the result of his detection of it in rutile 
and ilmenite, and in ignorance, apparently, of Gregor’s 
prior discovery, although this was announced in 
Crell’s Annalen of 1791. Klaproth’s experiments 
were confirmed by Vauquelin and Hecht in 1796. 
Klaproth subsequently examined menaccanite, and 
found that menachin and titanium were identical. 
The atomic weight of titanium was made the subject 
of investigation by Rose in 1823, and again in 1829 ; 
by Mosander in 1830; by Dumas in the same year ; 
by Pierre in 1847, and by Demoly in 1849. The 
methods employed were not identical, but they usually 

