A text-book of inorganic chemistry / by A.F. Holleman...rendered into English by Hermon C. Cooper with the co-operation of the author.

  • Holleman, A. F. (Arnold Frederick), 1859-1953.
Date:
1902
Catalogue details

Licence: In copyright

Credit: A text-book of inorganic chemistry / by A.F. Holleman...rendered into English by Hermon C. Cooper with the co-operation of the author. Source: Wellcome Collection.

    463/500 (page 445)
    AMMONIA COMPOUNDS OF TUB METALS. U 5 The same applies to the compounds of the second class. NH3 can be substituted by various other molecules and the compounds M(NH3)4X, can lose NH3 and go over into compounds which bear a definite relation to the former, e.g.: Pt(NH3)4Cl3 ; Pt(NH,),Cl, ; Pt(NH,)sCl, Plato-diammine chloride Plato-mono-diainniine chloride Platosammine chloride These two large classes of metal-ammonia compounds comprise all known compounds of this sort. Their classification is thus simple. 318. The loss of ammonia just referred to is accompanied by an im- portant change in the structure of these complex compounds. Let us take the luteo-chlorides as an example in order to discuss this. Their aqueous solutions are strongly ionized, as the high electrical conductivity shows. The existing ions must be [Co(NH3)6] and 3CT, for in the first place all the chlorine can be precipitated directly with a silver solution, wherefore all three chlorine atoms must exist as ions, and in the second place the solu- tion gives neither the ordinary reactions of cobalt nor those of ammonia. If, however, a luteo salt is converted into a purpureo salt by the loss of INHj, one of the halogen atoms loses at the same time the ability to act as an ion, which is evident from the fact that silver nitrate directly pre- cipitates but two thirds of the chlorine atoms from a dissolved purpureo- chloride solution; moreover the electrical conductivity is considerably less- ened. The same statements apply to the transformation of purpureo-chlo- ride into praseo-chloride, the latter of which can be shown in a similar manner to contain only chlorine ion in aqueous solution. Finally in the hexamine salts all ionization has disappeared ; the solution of hexamine- cobalt nitrite, Co(NH3)3(N03)3, for example, was found to be practically a non-conductor. It must therefore be assumed that the solution of a luteo salt contains the trivalent ion [Co(NH3j6] besides three anions; a solution of a purpureo salt, the bivalent ion j^Co^^?3^6 and two anions; a solution of the praseo salts, the univalent ion Co(NII3)4 A 2 and one anion; while in the hexa- mine compounds the complex (NH3)3 X3 is non-ionizable, or in other words neutral (nullivalent). Entirely analogous to this is the behavior of the compounds of the second class in their progressive loss of ammonia mole- cules. It is interesting in this connection to note that in the first class the number of groups, or elements substituting them, present in the complex ion in addition to the metal is always six, in the second class always four. Werner assumes that these are directly united with the metal, while the ionizable halogen atoms or negative groups are indirectly connected with the metallic atom through ammonia. 319. Not less worthy of note is the effect of still further substitution