210 
as forms of H 5n, or H5n + 1, they form a triad as well 
defined as their homologues of position in H3^, H2?i and 
H?i. Triads are also formed by antimony, arsenic, and 
phosphorus : — bismuth, antimony, and phosphorus — tanta- 
lum, niobium, and boron : — x = 140, As = 75 and B = 10 : — 
x = 140, Nb = 95, and Y = 50. The atomic weights of boron, 
phosphorus, and vanadium have been so carefully deter- 
mined by chemists, as to preclude any doubt of their being 
represented by H 5n + 1, rather than H on ; but the fact that 
arsenic, antimony, and bismuth are better represented by 
the formula H 5n, and that Cu, and Zn, in the series Hn, 
and IT2 n, exhibit the same constant minus difference from 
the classical atomic numbers as B, P, and Y, are further 
indications of some unknown property of the elements 
which conceals their exact multiple relations from view. 
If the discovery of two new elements of this group by Her- 
mann,* to which this chemist has given the names of 
neptunium, and illmenium be confirmed, the former element 
will have an atomic weight of 140, and the latter element 
an atomic weight of 165, as shown in the table. 
Although the numerical relations of the members of the 
series H on are very interesting, yet, it will be seen that the 
ratios are not so simple as those of the series H n, H2 n, H3 n, 
as multiples of the second member, minus the first, do not 
give the atomic weights of the other members of the series. 
The series H4 n 9 besides being incomplete by reason of the 
absence of several of its members, the atomicity of lanthanum 
and didymium is not yet agreed upon by chemists. There can, 
however, be no question as to the position of titanium as the 
third member of this series, as there is no other place vacant 
where an element with an atomic weight of 48 would fit, 
while the isomorphism of rutile with cassiterite and zirconia 
indicate the relation of tin and zirconium with the same 
series. 
* Nature, April 12th, 1877. H- Kolbe's Journal J'i.ir xn'akti^che chemie, 
Feb. 1877, p. 105—150. 
