VIII.

IV.—The Octahedral Groups.

These groups are at the turns of the spiral in Sir William Crookes' lemniscates (see p. 28). On the one side is carbon, with below it titanium and zirconium; on the other silicon, with germanium and tin. The characteristic form is an octahedron, rounded at the angles and a little depressed between the faces in consequence of the rounding; in fact, we did not, at first, recognize it as an octahedron, and we called it the "corded bale," the nearest likeness that struck us. The members of the group are all tetrads, and have eight funnels, opening on the eight faces of the octahedron. The first group is paramagnetic and positive; the corresponding one is diamagnetic and negative. The two groups are not closely allied in composition, though both titanium and tin have in common the five intersecting tetrahedra at their respective centres.

{ left 27 CARBON: One pair of funnels { right 22 { centre 1 -- 54 4 pairs of funnels of 54 atoms 216 Atomic weight 11.91 Number weight 216/18 12.00

TITANIUM: One carbon atom 216 4 c of 88 atoms 352 12 d of 14 " 168 Central globe 128 ---- Total 864 ---- Atomic weight 47.74 Number weight 864/18 48.00

ZIRCONIUM: One Carbon atom 216 4 c of 212 atoms 848 12 d of 36 " 432 Central globe 128 ---- Total 1624 ---- Atomic weight 89.85 Number weight 90.22

SILICON: 8 funnels of 65 atoms 520 Atomic weight 28.18 Number weight 520/18 28.88

GERMANIUM: 8 funnels of 156 atoms 1248 Central globe 52 ---- Total 1300 ---- Atomic weight 71.93 Number weight 1300/18 72.22

TIN: 8 funnels of 156 atoms 1248 6 spikes of 126 " 756 Central globe 120 ---- Total 2124 ---- Atomic weight 118.10 Number weight 2124/18 118.00

V.—The Bars Groups.

Here, for the first time, we find ourselves a little at issue with the accepted system of chemistry. Fluorine stands at the head of a group—called the inter-periodic—whereof the remaining members are (see Crookes' table, p. 28), manganese, iron, cobalt, nickel; ruthenium, rhodium, palladium; osmium, iridium, platinum. If we take all these as group V, we find that fluorine and manganese are violently forced into company with which they have hardly any points of relationship, and that they intrude into an otherwise very harmonious group of closely similar composition. Moreover, manganese reproduces the characteristic lithium "spike" and not the bars of those into whose company it is thrust, and it is thus allied with lithium, with which indeed it is almost identical. But lithium is placed by Crookes at the head of a group, the other members of which are potassium, rubidium and cæsium (the last not examined). Following these identities of composition, I think it is better to remove manganese and fluorine from their incongruous companions and place them with lithium and its allies as V a, the Spike Groups, marking, by the identity of number, similarities of arrangement which exist, and by the separation the differences of composition. It is worth while noting what Sir William Crookes, in his "Genesis of the Elements," remarks on the relations of the interperiodic group with its neighbours. He says: "These bodies are interperiodic because their atomic weights exclude them from the small periods into which the other elements fall, and because their chemical relations with some members of the neighbouring groups show that they are probably interperiodic in the sense of being in transition stages."

Group V in every case shows fourteen bars radiating from a centre as shown in iron, Plate IV, 1. While the form remains unchanged throughout, the increase of weight is gained by adding to the number of atoms contained in a bar. The group is made up, not of single chemical elements, as in all other cases, but of sub-groups, each containing three elements, and the relations within each sub-group are very close; moreover the weights only differ by two atoms per bar, making a weight difference of twenty-eight in the whole. Thus we have per bar:—

Iron 72 Palladium 136 Nickel 74 Osmium 245 Cobalt 76 Iridium 247 Ruthenium 132 Platinum A 249 Rhodium 134 Platinum B 257

It will be noticed (Plate XVII, 3, 4, 5,) that each bar has two sections, and that the three lower sections in iron, cobalt and nickel are identical; in the upper sections, iron has a cone of twenty-eight atoms, while cobalt and nickel have each three ovoids, and of these the middle ones alone differ, and that only in their upper globes, this globe being four-atomed in cobalt and six-atomed in nickel.

The long ovoids within each bar revolve round the central axis of the bar, remaining parallel with it, while each spins on its own axis; the iron cone spins round as though impaled on the axis.

14 bars of 72 atoms 1008 Atomic weight 55.47 Number weight 1008/18 56.00

14 bars of 74 atoms 1036 Atomic weight 57.70 Number weight 1036/18 57.55

14 bars of 76 atoms 1064 Atomic weight 58.30 Number weight 1064/18 59.11

(The weight of cobalt, as given in Erdmann's Lehrbuch, is 58.55, but Messrs. Parker and Sexton, in Nature, August 1, 1907, give the weight, as the result of their experiments, as 57.7.)

The next sub-group, ruthenium, rhodium, and palladium, has nothing to detain us. It will be observed that each bar contains eight segments, instead of the six of cobalt and nickel; that ruthenium and palladium have the same number of atoms in their upper ovoids, although in ruthenium a triplet and quartet represent the septet of palladium; and that in ruthenium and rhodium the lower ovoids are identical, though one has the order: sixteen, fourteen, sixteen, fourteen; and the other: fourteen, sixteen, fourteen, sixteen. One constantly asks oneself: What is the significance of these minute changes? Further investigators will probably discover the answer.

14 bars of 132 atoms 1848 Atomic weight 100.91 Number weight 1848/18 102.66

14 bars of 134 atoms 1876 Atomic weight 102.23 Number weight 1876/18 104.22

14 bars of 136 atoms 1904 Atomic weight 105.74 Number weight 1904/18 105.77

The third sub-group, osmium, iridium and platinum, is, of course, more complicated in its composition, but its builders succeed in preserving the bar form, gaining the necessary increase by a multiplication of contained spheres within the ovoids. Osmium has one peculiarity: the ovoid marked a (XVIII, 4) takes the place of axis in the upper half of the bar, and the three ovoids, marked b, revolve round it. In the lower half, the four ovoids, c, revolve round the central axis. In platinum, we have marked two forms as platinum A and platinum B, the latter having two four-atomed spheres (XVIII, 6 b) in the place of the two triplets marked a. It may well be that what we have called platinum B is not a variety of platinum, but a new element, the addition of two atoms in a bar being exactly that which separates the other elements within each of the sub-groups. It will be noticed that the four lower sections of the bars are identical in all the members of this sub-group, each ovoid containing thirty atoms. The upper ring of ovoids in iridium and platinum A are also identical, but for the substitution, in platinum A, of a quartet for a triplet in the second and third ovoids; their cones are identical, containing twenty-one atoms, like those of silver and tin.

14 bars of 245 atoms 3430 Atomic weight 189.55 Number weight 3430/18 190.55

14 bars of 247 atoms 3458 Atomic weight 191.11 Number weight 3458/18 192.11

14 bars of 249 atoms 3486 Atomic weight 193.66 Number weight 3486/18 193.34

14 bars of 251 atoms 3514 Atomic weight ------ Number weight 3514/18 195.22

V a.—The Spike Groups.

I place within this group lithium, potassium, rubidium, fluorine, and manganese, because of their similarity in internal composition. Manganese has fourteen spikes, arranged as in the iron group, but radiating from a central globe. Potassium has nine, rubidium has sixteen, in both cases radiating from a central globe. Lithium (Plate IV, 2) and fluorine (Plate IV, 3) are the two types which dominate the group, lithium supplying the spike which is reproduced in all of them, and fluorine the "nitrogen balloon" which appears in all save lithium. It will be seen that the natural affinities are strongly marked. They are all monads and paramagnetic; lithium, potassium and rubidium are positive, while fluorine and manganese are negative. We seem thus to have a pair, corresponding with each other, as in other cases, and the interperiodic group is left interperiodic and congruous within itself.

LITHIUM: Spike of 63 atoms 63 8 petals of 6 atoms 48 Central globe of 16 atoms 16 ---- Total 127 ---- Atomic weight 6.98 Number weight 127/18 7.05

POTASSIUM: 9 bars of 63 atoms 567 Central globe 134 ---- Total 701 ---- Atomic weight 38.94 Number weight 701/18 38.85

(The weight, as determined by Richards [Nature, July 18, 1907] is 39.114.)

RUBIDIUM: 16 spikes of 75 atoms 1200 Central globe 330 ---- Total 1530 ---- Atomic weight 84.85 Number weight 1530/18 85.00

The corresponding negative group consists only of fluorine and manganese, so far as our investigations have gone.

FLUORINE: 8 spikes of 15 atoms 120 2 balloons 220 ---- Total 340 ---- Atomic weight 18.90 Number weight 340/18 18.88

MANGANESE: 14 spikes of 63 atoms 882 Central balloon 110 ---- Total 992 ---- Atomic weight 54.57 Number weight 992/18 55.11