594 DR J. HALM ON 
which contains the five elements here considered we find also Hydrogen, which with 
regard to chemical valency is certainly related to our group of metals. Supposing, then, 
that Hydrogen belongs to the same group, we may, since we know the wave-frequency 
of the tail of its subsidiary series, compute its atomic volume. With v.=27426 we — 
find from the preceding equation 
423003 
a (52800 te 
: (Fa55) ee 
Since the atomic volume is defined as the atomic weight divided by the specific 
gravity of the substance in the solid state, we conclude that solid hydrogen should be 
14 times lighter than water. It is interesting to see that for the specific gravity of © 
the liquid at the lowest attainable temperature the same value was found by Professor 
DeEwak in his celebrated experiments on the liquefaction of gases. The close agreement 
may perhaps be accidental, especially since we do not know how much the specific 
gravity may change in the transformation of the gas from the liquid to the solid state, 
but nevertheless it seems that the new relation assigns to Hydrogen spectroscopically its 
correct position in the group of elements to which it is chemically related. The 
diticulty which appears in the attempt to connect, in this group, the position of the 
tails with the atomic weights, no longer comes in when atomic volumes are considered. 
In other groups the same relation, with altered constants, is noticeable. Thus we 
find : 
v 1/v Veg Comp. v 1/v Veo Comp. 
Mg: 137 0°41792 39780 39850 | Zn: well 0°47898 42925 42889 
Ca: 25°4 0°34019 33919 Bongo) Cd ebe:9 0°42638 40766 40840 
Sr: 34°8 0°30629 31060 SLIS0) 4 Hes La 0°40822 40168 40130 
Herp Ge Ho = 24298 ee eeee 
s/v xv 
On the other hand, however, the relation is not fulfilled for the elements Al, In, Tl, 
which Professor Kayser considers as a group of the third vertical column of 
MENDELEJEF’S system. But whether the three metals are indeed chemically co- 
ordinated, and should therefore be grouped together, is still somewhat doubtful. 
I am not contending, however, that the existence of the asserted relation between the 
wave-frequencies of the tails and the atomic volumes is conclusively proved by the 
preceding figures. So far as we may judge from the scanty materials at our disposal, 
we can only venture to say that indications in its favour seem to be present among the 
observations. Unfortunately it is not very probable that we shall learn more on 
this point in the future, as far as observations are concerned. Nevertheless the 
suggestion is perhaps valuable from the theoretical poimt of view, and for this reason a 
reference to it was thought advisable at this stage of the investigation. With regard to 
a 
