Liquids, variable valency

N. M. Emanuel, Z. K. Maizus, I. P. Skibida, and V. G. Vinogradova Homogeneous catalysis by compounds of variable valence metals in liquid-phase oxidation, pp. 131-159 (49). 

The other type of metals are the transition elements, which are less reactive, have variable valences, and tend to form complexes. In the solid and liquid states metals have metallic bonds, formed by positive ions with free electrons. See also metalloid non-metal. 

Redox mixed phases — are phases containing both the reduced and the oxidized form of a redox species. Whereas this case is trivial for liquid electrolyte solutions, it is of special significance for solid materials. In sohd phases under -> equilibrium conditions, this phenomenon requires a presence of variable-valence... 

Elements that can expand their valence shells commonly show variable covalence, the ability to form different numbers of covalent bonds. Elements that have variable covalence can form one number of bonds in some compounds and a different number in others. Phosphorus is an example. It reacts directly with a limited supply of chlorine to form the toxic, colorless liquid phosphorus trichloride ... 

In the metals, the same type of interatomic force acts between atom of different metals that acts between atoms of a single element. We have already stated that for this reason liquid solutions of many metals with each other exist in wide ranges of composition. There, are many other cases in which two substances ordinarily solid at room temperature are soluble in each other when liquefied. Thus, a great variety of molten ionic crystals are soluble in each other. And among the silicates and other substances held by valence bonds, the liquid phase permits a wide range of compositions. This is familiar from the glasses, which can have a continuous variability of composition and which can then supercool to essentially solid form, still with quite arbitrary compositions, and yet perfectly homogeneous structure. 

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