X-ray studies on the hydrous oxides
Milligan, W. O.
Doctor of Philosophy
The addition of a solution of an alkali hydroxide to a solution of a heavy metal salt usually gives a voluminous, gelatinous precipitate containing an amount of water depending upon the conditions of formation and subsequent treatment of the sample. While many of the cherished hydrates of the early investigators have been shown to be non-existent, in many cases modern methods of investigation have shown the situation in may cases to be such more complicated than it was formerly supposed. Examples of this will be given in following sections of this paper. For the purposes of this paper a hydrous oxide shall be defined as an adsorptive oxide containing an amount of adsorbed water depending upon the conditions of formation and treatment of the sample. A hydrate shall be considered to be a definite, crystalline, chemical compound. In most definite "hydroxides" it has been shown by x-ray analysis that the crystal lattice consists of metal ions and hydroxyl ions, and that in certain "hydrates", H2O groups are arranged around some central group after the manner of Werner complexes. "Hydroxides" may also contain additional chemically bound water over and above the true hydroxide. However, since in so many cases the complete structure has not been determined by x-ray analysis no attempt shall be made, in general, to distinguish between "hydroxides" and "hydrates". It is not considered that anything would be gained by using the terms "water of crystallization" and "water of constitution".