Carbon was joined with silicon, zirconium and titanium, while boron, being trivalent, was relegated to another group. A general classification of elements, however, was not realized by Frankland, nor even by Odling, who had also investigated the question from the valency standpoint.
Group III.: B, trivalent; Al, trivalent, but possibly also tetra-or penta-valent; Ga, divalent and trivalent; In, mono-, diand tri-valent; Tl, monovalent and trivalent..
Group V.: N, trivalent and pentavalent, but divalent in nitric oxide; P, As, Sb, Bi, trivalent and pentavalent, the last being possibly divalent in BiO and BiC1 2.
Group VIII.: Fe, Co, divalent and trivalent; Ni, divalent; Os, Ru, hexavalent and octavalent; Pd, Pt, divalent and tetravalent; Ir, tri-, tetraand hexa-valent.
If a certain minimum charge must be collected in order to start coagulation, it will need the conjunction of 6n monovalent, or 3n divalent, to equal the effect of 2n trivalent ions.
Is the sign of an alkali metal (potassium, sodium, rubidium, caesium), silver or ammonium, and M 111 denotes one of the trivalent metals, aluminium, chromium or ferric iron.
Such a reaction can only take place if the addition of the alkyl group takes place on the nitrogen atom of the isonitrile, from which it follows that the nitrogen atom must be trivalent and consequently the carbon atom divalent.
The average of the coagulative powers of salts of univalent, divalent and trivalent metals have been found by experiment to be proportional to the numbers 1: 35: 1023.
Similarly the trivalent phosphorus in the ordinary white form shows such resistance as if it were practically stable; on the other hand the red modification is in reality also stable, being formed, for instance, under the influence of light.
The first two give origin to well-defined series of salts, the ferrous salts, wherein the metal is divalent, and the ferric salts, wherein the metal is trivalent; the former readily pass into the latter on oxidation, and the latter into the former on reduction.