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Linnett and Poe, using the procedure of Zimmerman and Van Rysselberghe with hydrogen-like wave functions, found that the inter-bond angles formed by trivalent nitrogen would be expected to be a little less than the tetrahedral angle. In the present work it has been found, using the atomic wave functions of Duncanson and Coulson, that the angles would only be expected to be very slightly less than the tetrahedral. The quantitative result, though not the qualitative one, is therefore markedly dependent on the exact form used for the wave function. Similar calculations to those of Linnett and Poe were carried out for phosphorus to discover whether it was possible, by the method of Zimmerman and Van Rysselberghe, to account for the valency angle in PH3 being smaller than that in NH3. It was found that the simple application of that method did not account for this observed difference. An examination of valency angles in various hydrides and fluorides indicated that these are smaller the greater the electronegativity of the outer atom, or the smaller is the electronegativity of the central atom; and that they are also smaller the greater the number of lone pairs on the central atom. These conclusions are discussed.

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Zusammenfassung BesumeExperiments on the adsorption and Sedimentation of yttrium solutions have been carried out with solutions containing minimal suspended matter. It has been shown that such clean solutions of 'carrierfree' yttrium can be kept in polystyrene vessels, even at pH = 8 or more, with no Sedimentation taking place, and only a small amount of adsorption on to the vessel walls. It has also been shown that addition of 'Analar' water to such solutions converts the yttrium to a centrifugable form. It is suggested that the 'radiocoUoidal' properties of yttrium reported in the literature are due to ion exchange adsorption of yttrium ions on to suspended particulate matter and on to surfaces. Versuche über Adsorption und Sedimentation von gelöstem Yttrium wurden in Lösungen ausgeführt, die nur minimale Mengen suspendierten Materials enthalten. Es zeigte sich, daß solche reinen Lösungen "trägerfreien" Yttriums in Polystyrolgefäßen sogar bei pH 8 und mehr aufbewahrt werden können, wobei keine Sedimentation und nur wenig Adsorption an den Gefäßwänden auftritt. Bei Zusatz von "Analar"-Wasser wird das Yttrium zentrifugierbar. Wir glauben, daß die in der Literatur beschriebenen ,,radiokolloidalen" Eigenschaften des Yttriums von einer Austauschadsorption der Yttriumionen an suspendierte Partikelchen und an Oberflächen herrühren.Nous avons exp6riment6 sur l'adsorption et la Sedimentation d'yttrium dans des solutions ne contenant que des quantit^s minimales de matiere en suspension. Oes solutions pures d'yttrium sans entrameur peuvent etre conserv^es dans des r6cipients en polystyrene, meme ä pH 8 et au-dessus, sans Sedimentation et seulement une faible adsorption sur les parois. Par addition d'eau «Analar» l'yttrium prend une forme centrifugeable. Nous proposons d'expliquer les propriet^s radio-colloidales decrites dans la litterature par une absorption des ions d'yttrium par 6change sur les particules en suspension et les surfaces.

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