c. H. BRUBrlKER, JR.
4274 [CONTRIBUTION FROM
THE
Irol. 79
REDZIE CHEMICAL LABORATORY, MICHIGAXSTATEUNIVERSITY]
Activity Coefficients of Electrolytes of High Charge : Tris-(ethylenediamine)-platinum(IV) Perchlorate and Tris- (ethylenediamine)-cobalt (111) Chloride BY C. H. BRUBAKER, JR. RECEIVED -IPRII, 15, 1957 .Ictivity and osmotic coefficients of aqueous solutions of Pt(en)l(C10,)4and Co(en)9C13 have been determined a t 25' b y isopiestic comparison with KC1 solutions. Measurements have been made on solutions varying from about 0.05 nz t o C l ~ found to be 0.2229 and 1.110 m, respectively. T h e platisaturation. The solubilities of Pt(en)a(ClOa)d and C ~ ( e n ) ~were num complex appedrs t o be a strong 4-1 electrolyte, but the cobalt compound does not behave as a typical 3-1 salt.
-1s part of a program of investigation of the properties of solutions of electrolytes of high charge,',? two additional compounds, tris-(ethylenediamine)platinum(1V) perchlorate and tris-(ethylenediamine)-cobalt (111) chloride, which showed some promise of serving as representative electrolytes of high charge and large size, have been prepared and studied. The first seems to qualify as a 4-1 electrolyte, perhaps stronger than potassium octacyanomolybdate(IV), but the cobalt complex is very different in behavior from other 3-1 chlor i d e ~ . Osmotic ~ coefficients of these salts were determined by isopiestic comparison with potassium chloride solutions a t 23" and activity coefficients have been derived from the osmotic c0efficients.l Experimental The experimental procedure and apparatus were t h e same as in t h e previous work,2 with t h e exception t h a t t h e gold plated sample containers have been replaced with platinum ones. T h e temperature was 24.953 4~ 0.005'. Tris-(ethl-lenediarnine)-platinum(IV) perchlorate was prepared by a quantitative metathesis reaction between Pt(en):iClr2and -lgC104 in aqueous solution. .In excess of freshly prepared, nitrate free, .IgyO was treated with 0.1 2 1 1 HClOI and the resulting 0.1 JI .%gC104 solution was separated from the excess Xg,O bl- filtration. From this a 0.0580 11 solution was prepared. 2.1127 g. of Pt(en)sC14in 25 ml. of waterwastitratedwith t h e .kgCIOr solution and care was taken t h a t only a drop or two excess .IgCIOa was used. T h e silver chloride was filtered off after being digested on a steam-bath for one hour and t h e Pt(en),(C104)4was recovered b y evaporation. This product was dried in an oven a t SO" and was weighed. 3.1532 g . of Pt(en)a(CIOa)awas obtained; the theoretical yield would be 3.159 g. T h e Pt(en)z(CIOa)r was then recrystallized from water three times and was dried a t 70' and stored over barium oxide. This salt occurs as a hydrate in equilibrium with water a t room temperature, b u t much water is lost on standing in air and t h e compound can be completely dehydrated a t 70" or b y drying over barium oxide. T h e exact degree of hvdration m-as not determined, b u t there are probably 2 H J 0 or 2.5H20(compare Pt(en)3(SOs,)r.2H.05and Pt(en):iCl,.2.5H20).6 T h e anhydrous n i a t e r d does not absorb moisture from the air readily and was The form weighed in these experiments. Co(en)3Cla\vas prepared according t o t h e method in "Inorganic Syntheses"' and the product was purified by recrystallizing three times from water. T h e trihydrate is prepared by this process, b u t t h e water is removed by drying ;1) This program is supported by a research grant from T h e S a tional Science Foundation ( 2 ) C . H . Brubaker, Jr.. THIS J O U R N A L . 78, 5 7 6 2 (1950). I:
