130 REPORT—1883. 
SPECTRUM OF BERYLLIUM. 
Wave-lengths Description 
33201 . : : : . Strong sharp 
3129°9 ; . : . Very strong, extended 
26494. . . ; . Strong sharp 
2493°2. . ; ; . Strong sharp 
2477-7. F . : . Strong sharp 
The first two numbers differ slightly from those given in the ‘ Journal 
of the Chemical Society,’ but they are believed to be the more accurate. 
The previous measurements of the lines of beryllium were two given 
by Thalén? with wave-lengths 4487 and 4575, and two lines very close 
together given in Cornu’s map of the solar spectrum, wave-lengths 3130 
and 3130-4. It will be observed that in the spark spectrum there is 
only one line corresponding to'the first of the latter, with wave-length 
3129°9. There is probably a difference in this case between the are and 
the spark spectrum, because there is no difficulty in distinguishing be- 
tween two lines differing by 0°4, and under various conditions two lines 
have never been observed at this point in the spark spectrum. On the 
other hand such differences are by no means unusual. 
Regarding the views held by Emerson Reynolds, Nilson and 
Pettersson, and Brauner on the subject of beryllium, there may be a 
want of harmony in detail, but they at least agree in assigning a 
value, not greater than 13°8 and not less than 9-2, to its atomic weight. 
The former number implies that the metal is a triad, the latter that 
itis adyad. In the former case it must belong either to the series of 
elements of which aluminium, gallium, and iridium are members, or to a 
sub-group of rare earth metals to which yttrium and scandium belong. 
In attempting to accommodate the element with a position in either 
series we are met by a serious difficulty—viz., that not only is the atomic 
weight not in keeping with the periodic law (a point which cannot be 
discussed here), but its spectrum is altogether different from the spectra 
typical of either class. There is a periodic variation in the spectra of 
the elements as well as in their atomic weights and chemical properties, 
and we cannot put the periodic law out of mind in considering the position 
of beryllium. Now the spectra typical of the triad group, of which alu- 
minium and indium are the first and third terms, consist of three pairs of 
lines harmonically related, the intervals between the individuals of each 
pair increasing with increased refrangibility of the rays in each spectrum, 
while the intervals between the individuals in each pair in different spectra 
increase with the increase of atomic weight. The interval between each 
pair of lines contains an isolated ray. As the atomic weight of beryllium 
is less than that of aluminium, it should have a spectrum in which the 
same grouping appears, but the intervals between the pairs of lines should 
be shorter, and the individuals of each pair should be closer together. 
The lines of beryllium are not characteristically grouped like those of 
aluminium and indium, it cannot therefore belong to this series of 
elements. If we attempt to classify beryllium in a manner which accords 
with Nilson and Pettersson’s views,’ the elements scandium and yttrium, 
with atomic weights 44 and 89 respectively, must yield spectra typical of 
the series, and the similarity between the spectra of the two metals, 
1 June, 1883, p. 316. 2? Watt's Index of Spectra. 
% Proc. Roy. Soc. 1880, vol. 31, p. 37. 
